store managers' guide - ahdb potatoes · all recommendations in the store managers’ guide...
TRANSCRIPT
Store ManagersrsquoGuide
2 S T O R E m a n a g E R S rsquo g U I D E22
PotatoCouncilSuttonBridgeCropStorageresearchEastBankSuttonBridgeSpaldingLincolnshirePE129YDTel01406351444Fax01406351125E-mailsbcsrpotatoahdborgukWebwwwpotatoorguksbcsrFreephoneadviceline08000282111
WrittenbyAdrianCunningtonandRobertPringle
EditedbyAdrianCunningtonandKateJackson
AdditionalwritingbyAdrianBriddonRobertClaytonRichardCrowhurstKateJacksonAjayJinaSteveSaundersGraemeStroudampTimPrattPhotographybyTimScrivenerandGraemeStroudDesignbyMistralPublishedbyAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBPrintedon75recycledpaperusingvegetable-basedinksandchemistry-freeplatetechnologyinlinewiththeBritishPrintingIndustriesFederationrsquosenvironmentalpolicyonconservingenergyandnaturalresourcesandreducingwasteSecondedition2008reprinted2012Firstpublished2001copyAHDB20082012
AllrecommendationsintheStoreManagersrsquoGuidearegiveningoodfaithbutneitherAHDBPotatoCouncilnoritsauthorsresearchersadvisorsorcontractorscanbeheldliableforanylossinjuryordamagesuffereddirectlyorindirectlyfromtheuseofthisGuide
3S T O R E m a n a g E R S rsquo g U I D E 333
Introduction
thisisthesecondeditionofthePotatoCouncilrsquosStoreManagersrsquoGuideIthasbeenproducedtoofferacomprehensiveoverviewofbestpractice
inpotatostoremanagement
ManagementiskeyPotatostorageisacriticalcomponentofthepotatoproductionprocesswithsomecropsspendinglongerinstoragethantheydointhegroundItfollowsthereforethatpotatoesinstoresshouldbeaffordedasimilarlevelofmanagementinputasmightbeappliedtoagrowingcropThesituationinstoresisdynamicthecropisrespiringandreactingtoitsenvironmentStoreoperatorsmusthavethecapabilityndashinbothexpertiseandenvironmentalcontrolequipmentndashtorespondtothischangetooptimiseconditionsinthestoreandmaintainqualitythroughoutthestorageperiod
AcriticaltimeforpotatostorageMuchofthepotatostorageinGreatBritainhassufferedfromalengthyperiodwithoutmajorcapitalinvestmentManybusinessesnowfacecriticaldecisionsaboutthecontinuedsuitabilityofsomeolderstores
Thefirststeponthisdecision-makingpathisthestoreassessmentprocess(Section1)ThishelpstoidentifyanydeficienciesorareasforimprovementevaluationofperformanceprioritisationforoperationandsuitabilityforspecificusesHavingtherightequipmentforthejobisfundamentaltosuccessStorageisnotjustaboutkeepingpotatoesitisaboutmaintainingtheirqualitythroughoutthestorageperiodsothatitispossibletodeliverconsistentlyinaccordancewiththemarketspecificationataneconomicandsustainablecosttoearnaworthwhilereturn
ChangestoatrustedguideInupdatingthisguidethesametried-and-testedformathasbeenretainedandemphasishasbeenplacedonprovidingadvicewhichisapplicabletomoststorageinstallationsHowevertheopportunityhasalsobeentakentohighlightnewdevelopmentsandtechniqueswhichwillbeofinteresttothoselookingtomovetheirstorageforwardoverthecomingseasons
TopicswhichfeatureprominentlyinthePotatoCouncilrsquosresearchprioritiesincludebullDiseasemanagementbullChemicalresidueminimisationbullCostcontrolbullEnergyefficiencyandsustainability
Focusedissue-specificstrategieshavebeenintroducedandareanincreasinglyimportantaspectofpotatostoremanagementTheseincludebullThe Safe HavenschemeforthepreventionofnotifiablediseasesbullThePotato Industry CIPC Stewardship Action PlantoaddressallaspectsoftheuseofthesproutsuppressantPleaserefertowwwpotatoorgukcipcforthelatestinformation
FindingtheinformationyouneedTheguideiswritteninamodularformatwithcross-referencingsoyoucanmovebetweenthesectionswhicharerelevanttoyourstorageBestpracticeguidanceisbasedaroundinformationfromarangeofsourcessummarisedinthebibliography(Appendix1)
Muchoftheinformationisderivedfromlevy-fundedresearchanddevelopmentbutisalsosupportedbysomefromgovernmentindustryortheprivatesectorIfyouneedfurtherassistanceintheinterpretationoftheguidepleasecontacttheStorageAdviceLineon08000282111ore-mailsbcsrpotatoahdborguk
4 S T O R E m a n a g E R S rsquo g U I D E
Contents
IntroduCtIon 3
1 StorESELF-ASSESSMEnt 6 Aquickmethodofassessingastorersquoscapabilities
2 StorAGEBuILdInGS 10 Basicinformationontherequirementsforstoragebuildingsdiurnalvariation
3 CroPPHYSIoLoGY 12 Respirationdormancysugars
4 ControLoFStorAGEdISEASES 14 Whydiseasesdevelopinstoreintegratedcontrolcommonstoragediseases
5 StorEHYGIEnE 16 Keyrequirementsforminimisingdiseasecontaminationinstore
6 SErVICInGAndSEnSorS 18 Routinemaintenanceofequipmentandcalibrationofsensors
7 LoAdInGtHEStorE 20 Cropsamplingboxstackingspeedofloading
8 VEntILAtIon 22 Automationairflowratesspaceandpositivelyventilatedstores
9 drYInG 24 Removaloffreemoisturedryingfrontspositiveventilation
10 WoundHEALInGAndPuLL-doWn 26 Ratesofwoundhealingriskbasedmanagementtemperaturereduction
11 CondEnSAtIonontHECroP 28 Whycondensationonthecropoccursriskstothecrop
5S T O R E m a n a g E R S rsquo g U I D E
12 StruCturALCondEnSAtIon 30 Whystructuralcondensationoccurspreventativemeasuresroofspaceheating
13 rEFrIGErAtIon 32 Environmentalcontrolcoolingratesmaintenance
14 HuMIdItY 34 Humidityandmoisturelosshumidification
15 EnErGYMAnAGEMEnt 36 Monitoringexamplecostsoptimisinguse
16 StorEAtMoSPHErE 38 Oxygencarbondioxideothervolatiles
17 StorAGEForMArKEtS 40 CostscropmonitoringgettingthebestfromQCsampling
18 SProutSuPPrESSIon 44 RequirementforsproutcontrolactiveingredientsoptimisinguseofCIPC
19 WArMInG 46 Physicsofwarmingsystemstousedryingofskinsandlsquofingernailrsquodamage
20 StorEMonItorInGAndQuALItYASSurAnCE 48 Recordkeepingandprotocolsstoremonitoringanddatalogging
21 HEALtHAndSAFEtY 50 Workingatheightrisksinstoressafetyclothing
Appendices
1Bibliography 52
2Glossaryofterms 53
3Metricequivalents 54
4dew-pointtable 55
6 S T O R E m a n a g E R S rsquo g U I D E
1 Storeself-assessment
ForeachstorefeatureinthetableconsiderthefactorslistedandringthedescriptiononeachlinewhichbestsummarisesyourownstoreUsetheassessmenttoidentifythoseareaswhereimprovementscanbemade(anyscoring1asaminimum)andconsulttheappropriatesectionforfurtherinformationSomeproblemsmaybeeasytosolveandwillquicklyproducesignificantbenefitsothersmayneedlonger-termplanningtorectify
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
HYGIEnE
Cleaningfrequency
Mainmethodusedwhere
VErMInControL
HIGHrISKoFContAMInAtIonNocleaning
Sweeping
Nospecificmeasures
CleanedannuallyVacuumampdebrisremoval
Floorandwalls
Controlmeasuresinplacewithinstore
Vacuum+wash
+washboxesampmainsurfaces
VErYLoWdISEASErISKStorecleaneddaily+disinfectantapplied
+fogappliedtoentirestore
Accreditedprofessionalpestcontrolforfarm
Storehygiene
StruCturE
Storefabric
door(s)
Exposure
LEAKYPronEtoCondEnSAtIonLotoflightenters
2ormoregapsallround
Noshelter
Somelightenters
Door(s)sealedwithbrushesorrubber
Shelteredfromprevailingwind
Oddpinpricksoflight
Oneexternaldooronlysealedallround
Shelteredallround
SEALEdControLLABLECompletelydark
Noexternaldoorsloadviagradingarea
Singledoorexitstogradingarea
Storagebuildingsampcondensationonthecrop
InSuLAtIon
roof
Wall
noInSuLAtIon
Singleskinroof
Brickblockstonewalls
Doubleskin+glassfibreroof
Lightweightcavitywalls
lt75mmEEPsprayfoam
Compositepanel+gt50mmfoamEEP
HIGHLEVELInSuLAtIon75mm+foamEEPinsulation
Ascolumn3butgt75mm
Storagebuildings
7S T O R E m a n a g E R S rsquo g U I D E
bullringthedescriptionswhichmostcloselydescribeyourstorebullConsiderthefactorsandrisksthisself-assessmentidentifiesbulldecideonanyactionneededbullrefertotheappropriatesectionoftheguideorseekfurtherspecialistadvice
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
VEntILAtIon
Bulkstoresystem
Boxstoresystem
Boxstoreairdistribution
recirculation
HIGHrISKoFContAMInAtIonNofanopendooronly
Nofanopendooronly
Aroundboxesnosingleldquoairrollrdquoestablished
None
Fanslt002m3st
Fanslt002m3st
Spaceventilationformsrollofairpartviaboxapertures
Someairmovementbutnoairroll
Spaceventilationampfansge002m3st
Ascolumn2+rooffansorpositiveventilationwithtraditionalboxes
Intermittentlt002m3stLowratepartstore
PoSItIVEampFAStdrYInGFansge002m3st
Positiveventilationampfansge004m3st
Positiveventilationusingpurposedesignedboxes
Intermittentge002m3stLowratecontinuous
Ventilation
FAnSYStEMS
Fantype
Fanefficiency
Ventilationcontrol
Mixing
Inletairprotection
unControLLEdrISKtoCroP
Centrifugalfan
Oldagedfanwithbigstartingload
Onoffswitching
Manual
Nofrostthermostat
Axial(propellerstyle)
Modernfan(s)withpower-factorcorrection
Automaticswitchingofsinglemultiplefans
Autonoairmixing
Thermostattocutfanoffineventoffrost
Automatedaxialfans
High-efficiencyfansforlowrunningcost
Manualspeedcontrolofautomaticsinglemultiplefans
Auto+airmixing
Inlettemperaturecontrol
FuLLControLoFCooLInG
AxialfansforpositiveventilationSoftstarthigh-efficiencylownoisefans
Automatedvariablespeedcontroloffans
Auto+airmixingampdew-pointcontrol
Inlettemperature+condensationcontrol
Ventilation
8 S T O R E m a n a g E R S rsquo g U I D E
1 Storeself-assessment
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
BoXStACKInG
Spaceventilatedstores
Cross-stackedboxes(ieat90degtomainblock)
Boxheight
rEStrICtEdAIrFLoWrISKoFCondEnSAtIonBoxesstackedrandomly
Boxesstackedacrosspalletslotsofmainblock
Inconsistentstackingheightthroughoutstore
Gapsacrossstore(riskofshortcircuiting)
Boxescross-stackedawayfrommainblocktoallowairtoenterpalletapertures
Rowsateaves1boxlowercapacityeconomicsdictate
Gapsgt150mmbetweenrows
Slattedboxeslessrestrictivetoairflowwhencross-stackedifonly2wide
Allboxesatsameheight
oPtIMALAIrFLoWLoWrISKoFCondEnSAtIonGapslt150mmandsupplementaryfanstotargetlsquodeadspotsrsquo
Boxesstackedat90degtoairflowwith50mmgapsbetweenalternateboxeswithinrows
Allboxesatsameheightroofspaceventilatedheated
Loadingthestore
rEFrIGErAtIon
Fridgesystemsizeampperformance
Spaceventilationcoolingrate
Positiveventilationcoolingrate
dEHYdrAtIonrISK
Smallfridgecoilwithair-onair-offtempdifferencegt35degC
Longrunningtimesnoeffectivecooling
Asabove
Coolsatlt025degCday
Coolsatlt05degCday
Coolsatgt05degCday
Coolsatgt1degCday(ManagecondensationriskP11)
FrIdGESIZEoPtIMAL
Air-onair-offtemperaturedifference~25degC
Coolsat~05degCday
Coolsat~1degCday
Refrigeration
9S T O R E m a n a g E R S rsquo g U I D E
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
MonItorInGAndtrACEABILtY
temperaturesensors
Bulkstacksensorplacement
Condensationcontrol
Stockcontrol
Storerecording
LACKoFControL
Nosensorsinstore
Asabove
Asabove
Chemicalrecordsonlylegalminimum
Asabove
Inaironlycropconditionunknown
Topsurfaceonly-pronetoinfluencebyairabove
Controloftemperaturedifferentials
Chemicaluseplusstocklocationinstorerecorded
Occasionalmanualrecordingofstoretemperatures
1or2sensorsincropnomeasureoftemperaturevariation
Topandbaseofstacktomeasurepiletemperaturegradient
Relativehumiditymeasurementfordew-pointcontrol
Chemicalusestockdetailslabelledoneachbox
Regularmanualrecordingofstoretemperaturesandfanrunningtimes
FuLLCAPABILItY
1sensorper100tonnes
Ascolumn3butalso300mmdowntoanticipatecondensation
Skinresistancesensingtomeasureanywetting
Boxrecordsincludelocation-feedbackonstorageproblems
Automaticloggingofstoretemperaturesandfanrunningtimes
LoadingthestoreampStoremonitoringandqualityassurance
QCSAMPLInG Singlepointsampling Multi-pointsampling
ononelevelMulti-pointsamplingonmorethanonelevel
Comprehensivesamplingthroughoutthestore
Storageformarkets
SEEdGrAdInG
CondEnSAtIonrISK
Instore Nextdoorbutnoairlock
Nextdoorwithstripcurtain
StorEISoLAtEd
Nextdoorwithhighspeeddoor
Condensationonthecrop
10 S T O R E m a n a g E R S rsquo g U I D E
Fabricordoorleakagetowind-inducedventilationreducesthebenefitsofthestoreasitislikelytoleadtolossofenvironmentalcontrolcropweightlossandpossiblecondensationonthecropVentilationorrefrigerationrun-timewillincreasetocoolthecropwarmedbytheleakingair
ContainmentThecapitalcostofabulkstorewithload-bearinginsulatedretainingwallsishigherthanforaboxstoreButwhenthecapitalcostofboxesisaddedbulkstorageischeaperoverallBoxstoreseaseseparationfordifferentstocksandprovidemoreflexibilityforcropmovementandmarketingDeepbulkpilescanleadtopressurebruisingproblemsifthecropisstoredover40mhighorifexcessivelyventilatedbynon-humidifiedairBoxstorageisnormallyfreefrompressurebruisinganddependingontheirqualityboxescanbestackedupto8high
InsulationThequalityoftheinsulationwilldeterminetoalargeextenthowwellapotatostoreperformsInsulationisakeyfactorforapotatostoremuchmoresothanitisforgeneralpurposebuildings
MaintainingtemperaturesabovefreezingpointisseldomaproblemgiventhequantityofheatproducedinalargestoreHoweveranyheatthatleaksintoastorehastoberemovedbyexpendingenergyeitherintheformofventilationorrefrigerationInadditiontotheimplicationsoncosttheavoidableoperationofenvironmentalcontrol
2 Storagebuildings
Awellsealedandinsulatedpotatostore(Figure21)will
bullAllowthecroptobekeptatastabletemperaturelargelyunaffectedbydiurnalvariationandambientconditions
bullHelpmaintainarelativehumidityof90-100tominimisetuberweightloss
bullAllowcropstobestoredfreefromcondensationinchangeableweatherconditions
ControlledventilationControlledventilationallowscroprespirationheattoberemovedandthecroptobedriedandcooledFansarepositionedtocreateaflowofairthroughthecrop(positiveventilationbulkorbox)ortoformarollingmassofairthatwillflowoverthestackofboxesandthroughtheirpalletslots(spaceventilation)
Coolingcanbeachievedusingambientairandormechanicalcooling(refrigeration)Internalrecirculationofair(withoutcooling)canbeusedtoeliminatetemperaturevariationortodistributechemicalsforsproutsuppressionordiseasecontrol
AirflowshouldbeasuniformaspossiblethroughoutthestoretogiveevendryingandstablecroptemperaturesAwelldesignedstorewillhavebeenbalancedtoachieveuniformityofairflowatitstypicaloperatingconditionThismightincludefeaturessuchastaperedairductsorgraduatedlateraloutletstodeliversimilarquantitiesofairacrossthewholestore
Figure 21 A well sealed and insulated potato store
11S T O R E m a n a g E R S rsquo g U I D E
foundinpotatostoreswherecompositemetalpolyisocyanurate(PIR)sandwichpanelsareusedThesearecommonplacenowadaysfornewlybuiltstoresOthersystemsforupgradesofferatbestlittlemorethanavapourcheckThistendstolimitthechoiceofinsulationtoeithersprayorboardpolyurethaneoralternativelyexpandedextrudedpolystyreneboard
Specialistadviceshouldbesoughtforallaspectsofstoragebuildingdesign
equipmentwillalwaysincreasewaterlossfromthecropItisthereforejustasbeneficialtouseinsulationtolimitanyheatingressintothestoreasitistominimisetheeffectsofcoldweatherAlight-colouredreflectiveexternalsurfacewillreduceunwantedsolarradiationgains
NearlyallinsulationmaterialshavetheirperformancereducedsignificantlybyverysmallincreasesintheirmoisturecontentTheuseofvapourbarrierstoprotectinsulationisonlyeffectiveinthehighhumidityconditions
Storeassessment
bullUndertakeadetailedassessmentofyourstoreasdescribedinsection1
Balancedventilation
bullTheventilationsysteminastoreshouldbeinbalanceThismeansthatforoptimalperformancedesignfeaturesarerequiredndashegtaperedductsndashtooffsettheeffectsofpressuredropintheventilationsystemP8
doorsandlouvres
bullDoorsandlouvresaretheweakpointsoftheinsulationlsquoenvelopersquoMakesuretheycloseproperlyandstayclosedRegularpositiveactuationfromacontrollerisbeneficialforkeepingambientlouverswhicharesubjecttowindpressureclosed
Insulation
bullEnsurestoreinsulationisingoodconditionandeffective
bullWatchforsignsofcondensationwithinthestructurethatwilldegradetheinsulationvalueegdelaminatedinsulationboardswheremoisturehasgotinbehindthepanels
bullEnsureanynewbuildwithcompositeconstructionusesPIRpanelswhichareresistanttospreadofflameinthecoreintheeventoffire
ACTION POINTS
StorAGEBuILdInGS
Figure 22 Building envelope stabilises internal climate
12 S T O R E m a n a g E R S rsquo g U I D E
AllotherthingsbeingequalmoisturelossisafunctionofstorehumidityandairflowratePotatostoreswillusuallysettletoapproximately98relativehumidityandintheabsenceofahumidificationsystemthiswillbederivedbyevaporationofmoisturefromtubersInappropriatelyspecifiedrefrigerationunitscanexacerbatemoistureloss
dormancyFreshlyharvestedtubersusuallydonotsproutevenwhenconditionsareoptimalforsproutgrowthTheperiodoverwhichsproutgrowthisinhibitedbytuberphysiologyratherthanenvironmentalreasonsistermedthedormantperiodorsimplylsquodormancyrsquo
LargedifferencesindormancyoccurbetweenvarietiesWarmstoragetemperatureshaveadormancy-breakingeffectSelectionofvarietiesbydormancycharacteristicscanbeusefulforminimisingsprout-suppressantinputs
Dormancybreakistakenasthepointwhere50oftubershavesproutsof3mmormoreinlengthWarmdrysummerstendtoreducedormancy(inextremecasesleadingtosproutgrowthinthefieldbeforeharvest)whilecoolgrowingconditionswillgenerallyprolongitWaterlogginghasadormancy-breakingeffect
Woundhealing(curing)Wheretubershavebeensubjectedtowounding(egbyhandlingduringharvest)thetuberwillattempttohealthewoundndashaprocessinvolvingsuberisationandcell-divisionThespeedofthisprocesswhichisimportantforpreventingmoisturelossanddiseaseingressisaffectedbyanumberoffactorsTheseincludestoragetemperatureandhumiditywithwarmertemperaturesandhigherhumidityreducingthetimerequiredforwound-healing
Althougheffectivewound-healingisimportantconditionsthatareoptimalforcuringmayalsobesuitablefordiseasedevelopmentWherecropsareharvestedearlyundergoodconditionsorwherethestoragedurationislimitedsufficientcuringmayoccurduringtheperiodoverwhichcroptemperatureisreducedtotheholdingvalueP11
3 Cropphysiology
respirationPotatotubersarelivingorganismsandinstorecontinuetorespireandrespondtotheirenvironmentTheydosobyusingsugarsfromstarchinrespirationThisprocessconsumesoxygenandreleasescarbondioxideandsomeheatenergywhichimpactonstoragesystems
Respirationishighestatharvestandfallsrapidlytoabasallevelinthefirstweeksofstorage(Figure31)Respirationisgreaterinearly-liftedimmaturecropsthaninlate-liftedmaturecrops
Basalrespirationratedependspredominantlyonstoragetemperature(Figure32)Minimumrespirationrateisachievedataround5oCwiththerateincreasingaboveorbelowthistemperature
Handlingmechanicaldamageexposuretoethyleneandsproutingwillleadtoanincreaseinrespirationrate
EvaporationAlthoughsomemoistureislostintheprocessofrespirationmostislostbysimpleevaporationfromthetubersurfaceEffectivewound-healingandsproutcontrolisimportantinlimitingmoisturelossfromtubers
Figure 31 Respiration after lifting ndash early harvest
Figure 33 Moisture exchange between tuber skin and surrounding air in balance at ~98 relative humidity
Figure 32 Respiration in relation to storage temperature
1 2 3 4 5 6 7 8 9 10
Hea
t out
put (
Wto
nne)
35
0
5
10
15
20
25
30
Harvest date 9 September
Days after harvest
Harvest date 20 October
5 15 25
Rat
e of
resp
iratio
n (m
g C
O2k
ghr
)
12
0
2
4
6
8
10
Storage temperature (˚C)
13S T O R E m a n a g E R S rsquo g U I D E
ThisisaccomplishedsimplybyincreasingstoragetemperatureHoweverreconditioningleadstovariabilityinfrycolourandisthereforenotrecommendedasaroutinestoragepractice
PreconditioningmayalsobeusedtomaintainprocessingqualityHeretherearenodistinctcuringpull-downholdingperiodsandfrycolourorsugarcontentisusedtodeterminecropstoragetemperatureTemperaturereductiontoatargetholdingvalueonlyoccursprovidinggoodprocessingqualityismaintained
GreeningandglycoalkaloidsTubersexposedtolightwillturngreenwhichresultsfromthesynthesisofchlorophyllChlorophyllisitselfharmlessbutgreentubersaregenerallyrejectedbecausetheyhaveelevatedlevelsofglycoalkaloidsagroupofnaturaltoxicantspresentinpotatoes
TopreventgreeninginstorageexposuretolightshouldthereforebeminimisedalthoughtheneedtoseethecropclearlyandhealthandsafetyrequirementsP21willoverridethisduringloadingandsubsequentshortperiodswhenstoresareaccessedtobeinspectedorsampled
SugarsandconditioningPotatoescontainthreemainsugarsglucoseandfructose(monosaccharides)andsucrose(adisaccharide)AllthreesugarsaresweetandareimportantflavourcomponentsinwarepotatoesInpotatoesforprocessingthestoremanagerisprimarilyinterestedinthemonosaccharidesDuringprocessingthesereactwithothercomponentstoproducethebrowningwhichisassessedbymarketsasfrycolourAstoremanagersupplyingcropforprocessingmayalsobeinterestedinsucrosecontentAlthoughsucrosedoesnottakepartinbrowningreactionstrendsinsucroselevelsmaybeusedtohelpensurelowreducingsugarsandlightfrycolourduringstorage
VarietygrowthstageandstoragetemperatureareimportantindeterminingtubersugarcontentPotatoesexhibitlowtemperature-sweeteningwheresugarsaccumulatewithinthetuberastemperatureisreducedDuringstorageforprocessingtemperatureshouldthereforebemaintainedatthelowestlevelthatsafelymaintainsacceptablefrycolour
Forprocessingcropschangesinsugarcontent(andhencefrycolour)canbeachievedusingreconditioning
respiration
Thegreatertherespirationrateofthepotatoesthemorelikelyitisthatwarmairwillcondenseoncoolersurfacepotatoes
bullPositivelyventilatepotatoestoremoverespirationheattopreventsurfacecondensation
bullUsehighventilationratestopreventcondensationinheavilyrespiringearly-liftedorimmaturecropsP11
Evaporation
Moisturelossfrompotatoesduetoevaporationwilloccuriftherelativehumidity(RH)oftheairsurroundingthepotatoesislessthan98
bullKeepstorewell-sealedtominimiseweightloss
bullPreventuncontrolledexternalairingressasthisusuallyhasalowerRHthanthestorageenvironment
Sugars
Sugarsincreaseandfrycolourswilldarkenifpotatoesarestoredatcoldtemperatures
bullStorecropsforprocessingatc7-10degC
bullMonitorcold-storedpre-packpotatoesforeffectsofsugarincreaseontaste
bullIfunsurecheckstoragerequirementswithyourcustomer
ACTION POINTS
CroPPHYSIoLoGY
14 S T O R E m a n a g E R S rsquo g U I D E
Silverscurf Blackdot Skinspot dryrot Gangrene Softrot
moderateinfection
severeinfection
4 Controlofstoragediseases
DiseasecontrolisafundamentalcomponentofstoragemanagementMostdiseasesdonotoriginateinstoretheycomefromtwoprimarysourcestheseedorthesoilHowevermanyofthediseaseproblemsaffectingthepremiummarketscandeveloptosomedegreeinstoreandifnotcontrolledtheconsequencescanbecatastrophiceitherintermsofphysicalbreakdownofthecroporinlossofmarketvalueWhetherdiseasewilldevelopinstoreornot(Figure41)dependson
bullTheamountofinoculumusuallysporesorbacteriapresentonthetubersbullWhethermoisturenutrientsandtemperaturearesuitableforthediseasetogrowbullThenaturalresistanceofthetubertothediseaseorganism
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
15S T O R E m a n a g E R S rsquo g U I D E
Storemanagementallowsustoinfluencethisrelationshipparticularlyinrelationtothemicro-climatearoundthetubertocontroldiseasesduringstorage
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
Micro-climate Tuberresistance
Inoculum
Figure 41 Interaction between micro-climate and disease
notifiablediseases
SomediseasesarenotindigenousinBritainandtheirestablishmentwouldaffectthelong-termviabilityofthepotatoindustryIfsymptomsofeitherbrownrotorringrotaresuspectedthenimmediatecontactwithlocalDEFRAofficesorPlantHealthandSeedinspectorateisnecessaryVisitwwwdefragovukplanthphhtmemailplanthealthinfodefragsigovukortelephone01904455174toreportsuspectedcasesinEnglandandWalesInScotlandvisitwwwsasagovukplant_health
PreventativemeasuresexistGotowwwpotatoorguksafehaventolearnmoreaboutnationalschemesthatprotectseedandwarecrophealth
ringrotBrownrot
16 S T O R E m a n a g E R S rsquo g U I D E
Figure 52 Ensure dust and debris are removed from ducts
CrosscontaminationofsporesbetweenpotatostocksisinevitableFanventilationwithinthestoremayincreasethespeedofthismovementcomparedwithnaturalconvectionButtheairflowisabenefitasithelpskeepthecropfreefromcondensationpreventinganysporeswhichdosettlefromgerminating
MajordustmovementanddispersaloccurswhenforklifttrucksstirupdustonthefloorduringhandlingTheresultantdustcloudwillsettleontopofthecropwherethecondensationneededforgerminationismostlikelyIfgradingiscarriedoutwithinthestorethiswillalsocreateaconsiderabledustcloudwithsimilarconsequences
dustremovalSweepingwithabrushmovestheheavierdustparticlesalongthefloorwhilecreatingacloudoflighterparticleswhichincludesthemajorityofsporesVacuumingloosensandremovesallfractionsofdustandiffittedwithafinefilterwillremovemostharmfulsporesfromthestoreVacuumingisthereforemuchpreferredtosweeping
disinfectionRemovingdustandsquashedtuberswillremovethemajorityofinoculumpresentSomedustandsporeswillremainonthefloorwallsandraftersaswellasthefloorandsidesofpotatoboxesthemajorityofwhichcanberemovedbypowerwashingIftotalremovalofviablesporesisrequiredegforhighhealthcropsadisinfectantcanbeusedThisisparticularlyrelevantinstoreswheredamagerelateddiseasessuchasdryrothaveoccurred
5 Storehygiene
AcleanstorefreefromdiscardedtubersdustanddebrishasanumberofadvantagesItwillminimisecropinfectionimproveairflowcontributetoworkerhealthandcomfortandislikelytoimpressclientsandcustomers
SomesoilisinevitablybroughtintostorewiththeharvestedcropOncedrythisbecomesapotentialsourceofdustwhenthecropismovedIfthecropisfreeofdiseasewhenharvestedanditremainssooverthestorageperiodthenthedustwillbemainlymineralinnatureHoweverifthecropisdiseasedorbecomessoduringstoragethedustmaycontainlargequantitiesofsporeswhichwillbeasourceofinoculuminthepresentorfutureyears
dustdispersalConvectioncurrentscausedbyrespirationheatfromthecropwillcirculatedustandsporesthroughoutthestore
Figure 51 Vacuuming of potato store
17S T O R E m a n a g E R S rsquo g U I D E
StorEHYGIEnE
Post-storagecleaning
bullStore-cleaningshouldbeundertakenannuallyInboxstoresthisisbestcarriedoutimmediatelyafterthelastcrophasbeenremovedsocleanedboxescanbereturnedtostore
bullInayearfollowingcropinfectionbysilverscurforskinspotextrarigorouscleaningshouldbecarriedout
bullVacuumdirtanddebrisfromfloorsledgesbeamsandotherhorizontalsurfaces
bullWhereinsulationisdamagedorisroughandcollectsdustrepairandvacuum
bullOnlypowerhoseifinsulationismoisture-proof
Cleaningboxes
bullEnsurethatbox-tippersongradinglinesaredesignedtodischargethetotalboxcontentstogetridofmajorcontamination
bullUsepowerhosetocleanboxes
bullWherecleaningboxesisroutineconsidersettingupaconveyor-basedautomaticwashingsystem
bullPower-washboxesforhighhealthcrops
bullWherepossiblereturncleanedboxestostoreorkeepundercoverasthiscanextendboxlifeby70
Whentousedisinfectants
Forhighhealthseedcropsdisinfectantsmaybebeneficialespeciallyafteracontaminatedcropinthepreviousyear
bullUsedisinfectantmistfogorsprayaftervacuumingstore
bullSpraydisinfectboxeswhichhelddiseasedcropout-gradesorlsquobrockrsquo
bullFollowinggradingofdiseasedpotatoespower-washgradinglinethenspraywithdisinfectantwheregradinghighhealthcrops
bullAlwaysuseapprovedproductsandseekspecialistadvice
notesomedisinfectantsmaydamagestoreinsulationandelectricalfittingsndashconsulttheproductlabelbeforeuse
dailycleaning
bullVacuumthefloorparticularlyforkliftroutesandundergradersatleastonceaday
Gradinginstore
GradinginstoreislikelytoincreasetheamountofcontaminateddustinthestoreandthelikelihoodofambientairenteringthroughopendoorsDustprovidesdiseaseinoculumwhileambientairmaycausecondensationparticularlyonthetopsurfaceofboxesorpile
bullIdeallygradeinseparatebuildingwithaplasticstripdoorbetweenthestoreandgradingarea
bullIfgradinginstoreisunavoidableenclosepickersinwarmedcabinandfitadustcontrolsystemtotheline
bullFitdewpointtemperaturemonitortowarnofcondensationrisks
ACTION POINTS
LeavingboxesoutsidewillallowlighttokillviablesporesBoxesshouldnotbestackedmorethanfourboxeshighforsafetyandifstackedinpairsasmallgapbetweenrowswillallownatural(ultraviolet)lighttoreachonesideofeveryboxHoweveroutsidestackingcanreduceboxlifebyupto40
CleaningandenergyefficiencyMaintainingfansventilationandrefrigerationequipmentinacleanconditionwillhelpprolongtheirworkinglifeand
improvetheirworkingefficiencyEnsurethattemperatureandhumidityprobesarekeptcleanandinspectlouvresevaporatorsandcondensersIfnecessarycleanbyvacuumingorpowerwashingIfwashingtakecarearoundelectricalandmovingsystemsandensurethatanyresultingiceisremovedbydefrosting
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
2 S T O R E m a n a g E R S rsquo g U I D E22
PotatoCouncilSuttonBridgeCropStorageresearchEastBankSuttonBridgeSpaldingLincolnshirePE129YDTel01406351444Fax01406351125E-mailsbcsrpotatoahdborgukWebwwwpotatoorguksbcsrFreephoneadviceline08000282111
WrittenbyAdrianCunningtonandRobertPringle
EditedbyAdrianCunningtonandKateJackson
AdditionalwritingbyAdrianBriddonRobertClaytonRichardCrowhurstKateJacksonAjayJinaSteveSaundersGraemeStroudampTimPrattPhotographybyTimScrivenerandGraemeStroudDesignbyMistralPublishedbyAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBPrintedon75recycledpaperusingvegetable-basedinksandchemistry-freeplatetechnologyinlinewiththeBritishPrintingIndustriesFederationrsquosenvironmentalpolicyonconservingenergyandnaturalresourcesandreducingwasteSecondedition2008reprinted2012Firstpublished2001copyAHDB20082012
AllrecommendationsintheStoreManagersrsquoGuidearegiveningoodfaithbutneitherAHDBPotatoCouncilnoritsauthorsresearchersadvisorsorcontractorscanbeheldliableforanylossinjuryordamagesuffereddirectlyorindirectlyfromtheuseofthisGuide
3S T O R E m a n a g E R S rsquo g U I D E 333
Introduction
thisisthesecondeditionofthePotatoCouncilrsquosStoreManagersrsquoGuideIthasbeenproducedtoofferacomprehensiveoverviewofbestpractice
inpotatostoremanagement
ManagementiskeyPotatostorageisacriticalcomponentofthepotatoproductionprocesswithsomecropsspendinglongerinstoragethantheydointhegroundItfollowsthereforethatpotatoesinstoresshouldbeaffordedasimilarlevelofmanagementinputasmightbeappliedtoagrowingcropThesituationinstoresisdynamicthecropisrespiringandreactingtoitsenvironmentStoreoperatorsmusthavethecapabilityndashinbothexpertiseandenvironmentalcontrolequipmentndashtorespondtothischangetooptimiseconditionsinthestoreandmaintainqualitythroughoutthestorageperiod
AcriticaltimeforpotatostorageMuchofthepotatostorageinGreatBritainhassufferedfromalengthyperiodwithoutmajorcapitalinvestmentManybusinessesnowfacecriticaldecisionsaboutthecontinuedsuitabilityofsomeolderstores
Thefirststeponthisdecision-makingpathisthestoreassessmentprocess(Section1)ThishelpstoidentifyanydeficienciesorareasforimprovementevaluationofperformanceprioritisationforoperationandsuitabilityforspecificusesHavingtherightequipmentforthejobisfundamentaltosuccessStorageisnotjustaboutkeepingpotatoesitisaboutmaintainingtheirqualitythroughoutthestorageperiodsothatitispossibletodeliverconsistentlyinaccordancewiththemarketspecificationataneconomicandsustainablecosttoearnaworthwhilereturn
ChangestoatrustedguideInupdatingthisguidethesametried-and-testedformathasbeenretainedandemphasishasbeenplacedonprovidingadvicewhichisapplicabletomoststorageinstallationsHowevertheopportunityhasalsobeentakentohighlightnewdevelopmentsandtechniqueswhichwillbeofinteresttothoselookingtomovetheirstorageforwardoverthecomingseasons
TopicswhichfeatureprominentlyinthePotatoCouncilrsquosresearchprioritiesincludebullDiseasemanagementbullChemicalresidueminimisationbullCostcontrolbullEnergyefficiencyandsustainability
Focusedissue-specificstrategieshavebeenintroducedandareanincreasinglyimportantaspectofpotatostoremanagementTheseincludebullThe Safe HavenschemeforthepreventionofnotifiablediseasesbullThePotato Industry CIPC Stewardship Action PlantoaddressallaspectsoftheuseofthesproutsuppressantPleaserefertowwwpotatoorgukcipcforthelatestinformation
FindingtheinformationyouneedTheguideiswritteninamodularformatwithcross-referencingsoyoucanmovebetweenthesectionswhicharerelevanttoyourstorageBestpracticeguidanceisbasedaroundinformationfromarangeofsourcessummarisedinthebibliography(Appendix1)
Muchoftheinformationisderivedfromlevy-fundedresearchanddevelopmentbutisalsosupportedbysomefromgovernmentindustryortheprivatesectorIfyouneedfurtherassistanceintheinterpretationoftheguidepleasecontacttheStorageAdviceLineon08000282111ore-mailsbcsrpotatoahdborguk
4 S T O R E m a n a g E R S rsquo g U I D E
Contents
IntroduCtIon 3
1 StorESELF-ASSESSMEnt 6 Aquickmethodofassessingastorersquoscapabilities
2 StorAGEBuILdInGS 10 Basicinformationontherequirementsforstoragebuildingsdiurnalvariation
3 CroPPHYSIoLoGY 12 Respirationdormancysugars
4 ControLoFStorAGEdISEASES 14 Whydiseasesdevelopinstoreintegratedcontrolcommonstoragediseases
5 StorEHYGIEnE 16 Keyrequirementsforminimisingdiseasecontaminationinstore
6 SErVICInGAndSEnSorS 18 Routinemaintenanceofequipmentandcalibrationofsensors
7 LoAdInGtHEStorE 20 Cropsamplingboxstackingspeedofloading
8 VEntILAtIon 22 Automationairflowratesspaceandpositivelyventilatedstores
9 drYInG 24 Removaloffreemoisturedryingfrontspositiveventilation
10 WoundHEALInGAndPuLL-doWn 26 Ratesofwoundhealingriskbasedmanagementtemperaturereduction
11 CondEnSAtIonontHECroP 28 Whycondensationonthecropoccursriskstothecrop
5S T O R E m a n a g E R S rsquo g U I D E
12 StruCturALCondEnSAtIon 30 Whystructuralcondensationoccurspreventativemeasuresroofspaceheating
13 rEFrIGErAtIon 32 Environmentalcontrolcoolingratesmaintenance
14 HuMIdItY 34 Humidityandmoisturelosshumidification
15 EnErGYMAnAGEMEnt 36 Monitoringexamplecostsoptimisinguse
16 StorEAtMoSPHErE 38 Oxygencarbondioxideothervolatiles
17 StorAGEForMArKEtS 40 CostscropmonitoringgettingthebestfromQCsampling
18 SProutSuPPrESSIon 44 RequirementforsproutcontrolactiveingredientsoptimisinguseofCIPC
19 WArMInG 46 Physicsofwarmingsystemstousedryingofskinsandlsquofingernailrsquodamage
20 StorEMonItorInGAndQuALItYASSurAnCE 48 Recordkeepingandprotocolsstoremonitoringanddatalogging
21 HEALtHAndSAFEtY 50 Workingatheightrisksinstoressafetyclothing
Appendices
1Bibliography 52
2Glossaryofterms 53
3Metricequivalents 54
4dew-pointtable 55
6 S T O R E m a n a g E R S rsquo g U I D E
1 Storeself-assessment
ForeachstorefeatureinthetableconsiderthefactorslistedandringthedescriptiononeachlinewhichbestsummarisesyourownstoreUsetheassessmenttoidentifythoseareaswhereimprovementscanbemade(anyscoring1asaminimum)andconsulttheappropriatesectionforfurtherinformationSomeproblemsmaybeeasytosolveandwillquicklyproducesignificantbenefitsothersmayneedlonger-termplanningtorectify
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
HYGIEnE
Cleaningfrequency
Mainmethodusedwhere
VErMInControL
HIGHrISKoFContAMInAtIonNocleaning
Sweeping
Nospecificmeasures
CleanedannuallyVacuumampdebrisremoval
Floorandwalls
Controlmeasuresinplacewithinstore
Vacuum+wash
+washboxesampmainsurfaces
VErYLoWdISEASErISKStorecleaneddaily+disinfectantapplied
+fogappliedtoentirestore
Accreditedprofessionalpestcontrolforfarm
Storehygiene
StruCturE
Storefabric
door(s)
Exposure
LEAKYPronEtoCondEnSAtIonLotoflightenters
2ormoregapsallround
Noshelter
Somelightenters
Door(s)sealedwithbrushesorrubber
Shelteredfromprevailingwind
Oddpinpricksoflight
Oneexternaldooronlysealedallround
Shelteredallround
SEALEdControLLABLECompletelydark
Noexternaldoorsloadviagradingarea
Singledoorexitstogradingarea
Storagebuildingsampcondensationonthecrop
InSuLAtIon
roof
Wall
noInSuLAtIon
Singleskinroof
Brickblockstonewalls
Doubleskin+glassfibreroof
Lightweightcavitywalls
lt75mmEEPsprayfoam
Compositepanel+gt50mmfoamEEP
HIGHLEVELInSuLAtIon75mm+foamEEPinsulation
Ascolumn3butgt75mm
Storagebuildings
7S T O R E m a n a g E R S rsquo g U I D E
bullringthedescriptionswhichmostcloselydescribeyourstorebullConsiderthefactorsandrisksthisself-assessmentidentifiesbulldecideonanyactionneededbullrefertotheappropriatesectionoftheguideorseekfurtherspecialistadvice
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
VEntILAtIon
Bulkstoresystem
Boxstoresystem
Boxstoreairdistribution
recirculation
HIGHrISKoFContAMInAtIonNofanopendooronly
Nofanopendooronly
Aroundboxesnosingleldquoairrollrdquoestablished
None
Fanslt002m3st
Fanslt002m3st
Spaceventilationformsrollofairpartviaboxapertures
Someairmovementbutnoairroll
Spaceventilationampfansge002m3st
Ascolumn2+rooffansorpositiveventilationwithtraditionalboxes
Intermittentlt002m3stLowratepartstore
PoSItIVEampFAStdrYInGFansge002m3st
Positiveventilationampfansge004m3st
Positiveventilationusingpurposedesignedboxes
Intermittentge002m3stLowratecontinuous
Ventilation
FAnSYStEMS
Fantype
Fanefficiency
Ventilationcontrol
Mixing
Inletairprotection
unControLLEdrISKtoCroP
Centrifugalfan
Oldagedfanwithbigstartingload
Onoffswitching
Manual
Nofrostthermostat
Axial(propellerstyle)
Modernfan(s)withpower-factorcorrection
Automaticswitchingofsinglemultiplefans
Autonoairmixing
Thermostattocutfanoffineventoffrost
Automatedaxialfans
High-efficiencyfansforlowrunningcost
Manualspeedcontrolofautomaticsinglemultiplefans
Auto+airmixing
Inlettemperaturecontrol
FuLLControLoFCooLInG
AxialfansforpositiveventilationSoftstarthigh-efficiencylownoisefans
Automatedvariablespeedcontroloffans
Auto+airmixingampdew-pointcontrol
Inlettemperature+condensationcontrol
Ventilation
8 S T O R E m a n a g E R S rsquo g U I D E
1 Storeself-assessment
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
BoXStACKInG
Spaceventilatedstores
Cross-stackedboxes(ieat90degtomainblock)
Boxheight
rEStrICtEdAIrFLoWrISKoFCondEnSAtIonBoxesstackedrandomly
Boxesstackedacrosspalletslotsofmainblock
Inconsistentstackingheightthroughoutstore
Gapsacrossstore(riskofshortcircuiting)
Boxescross-stackedawayfrommainblocktoallowairtoenterpalletapertures
Rowsateaves1boxlowercapacityeconomicsdictate
Gapsgt150mmbetweenrows
Slattedboxeslessrestrictivetoairflowwhencross-stackedifonly2wide
Allboxesatsameheight
oPtIMALAIrFLoWLoWrISKoFCondEnSAtIonGapslt150mmandsupplementaryfanstotargetlsquodeadspotsrsquo
Boxesstackedat90degtoairflowwith50mmgapsbetweenalternateboxeswithinrows
Allboxesatsameheightroofspaceventilatedheated
Loadingthestore
rEFrIGErAtIon
Fridgesystemsizeampperformance
Spaceventilationcoolingrate
Positiveventilationcoolingrate
dEHYdrAtIonrISK
Smallfridgecoilwithair-onair-offtempdifferencegt35degC
Longrunningtimesnoeffectivecooling
Asabove
Coolsatlt025degCday
Coolsatlt05degCday
Coolsatgt05degCday
Coolsatgt1degCday(ManagecondensationriskP11)
FrIdGESIZEoPtIMAL
Air-onair-offtemperaturedifference~25degC
Coolsat~05degCday
Coolsat~1degCday
Refrigeration
9S T O R E m a n a g E R S rsquo g U I D E
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
MonItorInGAndtrACEABILtY
temperaturesensors
Bulkstacksensorplacement
Condensationcontrol
Stockcontrol
Storerecording
LACKoFControL
Nosensorsinstore
Asabove
Asabove
Chemicalrecordsonlylegalminimum
Asabove
Inaironlycropconditionunknown
Topsurfaceonly-pronetoinfluencebyairabove
Controloftemperaturedifferentials
Chemicaluseplusstocklocationinstorerecorded
Occasionalmanualrecordingofstoretemperatures
1or2sensorsincropnomeasureoftemperaturevariation
Topandbaseofstacktomeasurepiletemperaturegradient
Relativehumiditymeasurementfordew-pointcontrol
Chemicalusestockdetailslabelledoneachbox
Regularmanualrecordingofstoretemperaturesandfanrunningtimes
FuLLCAPABILItY
1sensorper100tonnes
Ascolumn3butalso300mmdowntoanticipatecondensation
Skinresistancesensingtomeasureanywetting
Boxrecordsincludelocation-feedbackonstorageproblems
Automaticloggingofstoretemperaturesandfanrunningtimes
LoadingthestoreampStoremonitoringandqualityassurance
QCSAMPLInG Singlepointsampling Multi-pointsampling
ononelevelMulti-pointsamplingonmorethanonelevel
Comprehensivesamplingthroughoutthestore
Storageformarkets
SEEdGrAdInG
CondEnSAtIonrISK
Instore Nextdoorbutnoairlock
Nextdoorwithstripcurtain
StorEISoLAtEd
Nextdoorwithhighspeeddoor
Condensationonthecrop
10 S T O R E m a n a g E R S rsquo g U I D E
Fabricordoorleakagetowind-inducedventilationreducesthebenefitsofthestoreasitislikelytoleadtolossofenvironmentalcontrolcropweightlossandpossiblecondensationonthecropVentilationorrefrigerationrun-timewillincreasetocoolthecropwarmedbytheleakingair
ContainmentThecapitalcostofabulkstorewithload-bearinginsulatedretainingwallsishigherthanforaboxstoreButwhenthecapitalcostofboxesisaddedbulkstorageischeaperoverallBoxstoreseaseseparationfordifferentstocksandprovidemoreflexibilityforcropmovementandmarketingDeepbulkpilescanleadtopressurebruisingproblemsifthecropisstoredover40mhighorifexcessivelyventilatedbynon-humidifiedairBoxstorageisnormallyfreefrompressurebruisinganddependingontheirqualityboxescanbestackedupto8high
InsulationThequalityoftheinsulationwilldeterminetoalargeextenthowwellapotatostoreperformsInsulationisakeyfactorforapotatostoremuchmoresothanitisforgeneralpurposebuildings
MaintainingtemperaturesabovefreezingpointisseldomaproblemgiventhequantityofheatproducedinalargestoreHoweveranyheatthatleaksintoastorehastoberemovedbyexpendingenergyeitherintheformofventilationorrefrigerationInadditiontotheimplicationsoncosttheavoidableoperationofenvironmentalcontrol
2 Storagebuildings
Awellsealedandinsulatedpotatostore(Figure21)will
bullAllowthecroptobekeptatastabletemperaturelargelyunaffectedbydiurnalvariationandambientconditions
bullHelpmaintainarelativehumidityof90-100tominimisetuberweightloss
bullAllowcropstobestoredfreefromcondensationinchangeableweatherconditions
ControlledventilationControlledventilationallowscroprespirationheattoberemovedandthecroptobedriedandcooledFansarepositionedtocreateaflowofairthroughthecrop(positiveventilationbulkorbox)ortoformarollingmassofairthatwillflowoverthestackofboxesandthroughtheirpalletslots(spaceventilation)
Coolingcanbeachievedusingambientairandormechanicalcooling(refrigeration)Internalrecirculationofair(withoutcooling)canbeusedtoeliminatetemperaturevariationortodistributechemicalsforsproutsuppressionordiseasecontrol
AirflowshouldbeasuniformaspossiblethroughoutthestoretogiveevendryingandstablecroptemperaturesAwelldesignedstorewillhavebeenbalancedtoachieveuniformityofairflowatitstypicaloperatingconditionThismightincludefeaturessuchastaperedairductsorgraduatedlateraloutletstodeliversimilarquantitiesofairacrossthewholestore
Figure 21 A well sealed and insulated potato store
11S T O R E m a n a g E R S rsquo g U I D E
foundinpotatostoreswherecompositemetalpolyisocyanurate(PIR)sandwichpanelsareusedThesearecommonplacenowadaysfornewlybuiltstoresOthersystemsforupgradesofferatbestlittlemorethanavapourcheckThistendstolimitthechoiceofinsulationtoeithersprayorboardpolyurethaneoralternativelyexpandedextrudedpolystyreneboard
Specialistadviceshouldbesoughtforallaspectsofstoragebuildingdesign
equipmentwillalwaysincreasewaterlossfromthecropItisthereforejustasbeneficialtouseinsulationtolimitanyheatingressintothestoreasitistominimisetheeffectsofcoldweatherAlight-colouredreflectiveexternalsurfacewillreduceunwantedsolarradiationgains
NearlyallinsulationmaterialshavetheirperformancereducedsignificantlybyverysmallincreasesintheirmoisturecontentTheuseofvapourbarrierstoprotectinsulationisonlyeffectiveinthehighhumidityconditions
Storeassessment
bullUndertakeadetailedassessmentofyourstoreasdescribedinsection1
Balancedventilation
bullTheventilationsysteminastoreshouldbeinbalanceThismeansthatforoptimalperformancedesignfeaturesarerequiredndashegtaperedductsndashtooffsettheeffectsofpressuredropintheventilationsystemP8
doorsandlouvres
bullDoorsandlouvresaretheweakpointsoftheinsulationlsquoenvelopersquoMakesuretheycloseproperlyandstayclosedRegularpositiveactuationfromacontrollerisbeneficialforkeepingambientlouverswhicharesubjecttowindpressureclosed
Insulation
bullEnsurestoreinsulationisingoodconditionandeffective
bullWatchforsignsofcondensationwithinthestructurethatwilldegradetheinsulationvalueegdelaminatedinsulationboardswheremoisturehasgotinbehindthepanels
bullEnsureanynewbuildwithcompositeconstructionusesPIRpanelswhichareresistanttospreadofflameinthecoreintheeventoffire
ACTION POINTS
StorAGEBuILdInGS
Figure 22 Building envelope stabilises internal climate
12 S T O R E m a n a g E R S rsquo g U I D E
AllotherthingsbeingequalmoisturelossisafunctionofstorehumidityandairflowratePotatostoreswillusuallysettletoapproximately98relativehumidityandintheabsenceofahumidificationsystemthiswillbederivedbyevaporationofmoisturefromtubersInappropriatelyspecifiedrefrigerationunitscanexacerbatemoistureloss
dormancyFreshlyharvestedtubersusuallydonotsproutevenwhenconditionsareoptimalforsproutgrowthTheperiodoverwhichsproutgrowthisinhibitedbytuberphysiologyratherthanenvironmentalreasonsistermedthedormantperiodorsimplylsquodormancyrsquo
LargedifferencesindormancyoccurbetweenvarietiesWarmstoragetemperatureshaveadormancy-breakingeffectSelectionofvarietiesbydormancycharacteristicscanbeusefulforminimisingsprout-suppressantinputs
Dormancybreakistakenasthepointwhere50oftubershavesproutsof3mmormoreinlengthWarmdrysummerstendtoreducedormancy(inextremecasesleadingtosproutgrowthinthefieldbeforeharvest)whilecoolgrowingconditionswillgenerallyprolongitWaterlogginghasadormancy-breakingeffect
Woundhealing(curing)Wheretubershavebeensubjectedtowounding(egbyhandlingduringharvest)thetuberwillattempttohealthewoundndashaprocessinvolvingsuberisationandcell-divisionThespeedofthisprocesswhichisimportantforpreventingmoisturelossanddiseaseingressisaffectedbyanumberoffactorsTheseincludestoragetemperatureandhumiditywithwarmertemperaturesandhigherhumidityreducingthetimerequiredforwound-healing
Althougheffectivewound-healingisimportantconditionsthatareoptimalforcuringmayalsobesuitablefordiseasedevelopmentWherecropsareharvestedearlyundergoodconditionsorwherethestoragedurationislimitedsufficientcuringmayoccurduringtheperiodoverwhichcroptemperatureisreducedtotheholdingvalueP11
3 Cropphysiology
respirationPotatotubersarelivingorganismsandinstorecontinuetorespireandrespondtotheirenvironmentTheydosobyusingsugarsfromstarchinrespirationThisprocessconsumesoxygenandreleasescarbondioxideandsomeheatenergywhichimpactonstoragesystems
Respirationishighestatharvestandfallsrapidlytoabasallevelinthefirstweeksofstorage(Figure31)Respirationisgreaterinearly-liftedimmaturecropsthaninlate-liftedmaturecrops
Basalrespirationratedependspredominantlyonstoragetemperature(Figure32)Minimumrespirationrateisachievedataround5oCwiththerateincreasingaboveorbelowthistemperature
Handlingmechanicaldamageexposuretoethyleneandsproutingwillleadtoanincreaseinrespirationrate
EvaporationAlthoughsomemoistureislostintheprocessofrespirationmostislostbysimpleevaporationfromthetubersurfaceEffectivewound-healingandsproutcontrolisimportantinlimitingmoisturelossfromtubers
Figure 31 Respiration after lifting ndash early harvest
Figure 33 Moisture exchange between tuber skin and surrounding air in balance at ~98 relative humidity
Figure 32 Respiration in relation to storage temperature
1 2 3 4 5 6 7 8 9 10
Hea
t out
put (
Wto
nne)
35
0
5
10
15
20
25
30
Harvest date 9 September
Days after harvest
Harvest date 20 October
5 15 25
Rat
e of
resp
iratio
n (m
g C
O2k
ghr
)
12
0
2
4
6
8
10
Storage temperature (˚C)
13S T O R E m a n a g E R S rsquo g U I D E
ThisisaccomplishedsimplybyincreasingstoragetemperatureHoweverreconditioningleadstovariabilityinfrycolourandisthereforenotrecommendedasaroutinestoragepractice
PreconditioningmayalsobeusedtomaintainprocessingqualityHeretherearenodistinctcuringpull-downholdingperiodsandfrycolourorsugarcontentisusedtodeterminecropstoragetemperatureTemperaturereductiontoatargetholdingvalueonlyoccursprovidinggoodprocessingqualityismaintained
GreeningandglycoalkaloidsTubersexposedtolightwillturngreenwhichresultsfromthesynthesisofchlorophyllChlorophyllisitselfharmlessbutgreentubersaregenerallyrejectedbecausetheyhaveelevatedlevelsofglycoalkaloidsagroupofnaturaltoxicantspresentinpotatoes
TopreventgreeninginstorageexposuretolightshouldthereforebeminimisedalthoughtheneedtoseethecropclearlyandhealthandsafetyrequirementsP21willoverridethisduringloadingandsubsequentshortperiodswhenstoresareaccessedtobeinspectedorsampled
SugarsandconditioningPotatoescontainthreemainsugarsglucoseandfructose(monosaccharides)andsucrose(adisaccharide)AllthreesugarsaresweetandareimportantflavourcomponentsinwarepotatoesInpotatoesforprocessingthestoremanagerisprimarilyinterestedinthemonosaccharidesDuringprocessingthesereactwithothercomponentstoproducethebrowningwhichisassessedbymarketsasfrycolourAstoremanagersupplyingcropforprocessingmayalsobeinterestedinsucrosecontentAlthoughsucrosedoesnottakepartinbrowningreactionstrendsinsucroselevelsmaybeusedtohelpensurelowreducingsugarsandlightfrycolourduringstorage
VarietygrowthstageandstoragetemperatureareimportantindeterminingtubersugarcontentPotatoesexhibitlowtemperature-sweeteningwheresugarsaccumulatewithinthetuberastemperatureisreducedDuringstorageforprocessingtemperatureshouldthereforebemaintainedatthelowestlevelthatsafelymaintainsacceptablefrycolour
Forprocessingcropschangesinsugarcontent(andhencefrycolour)canbeachievedusingreconditioning
respiration
Thegreatertherespirationrateofthepotatoesthemorelikelyitisthatwarmairwillcondenseoncoolersurfacepotatoes
bullPositivelyventilatepotatoestoremoverespirationheattopreventsurfacecondensation
bullUsehighventilationratestopreventcondensationinheavilyrespiringearly-liftedorimmaturecropsP11
Evaporation
Moisturelossfrompotatoesduetoevaporationwilloccuriftherelativehumidity(RH)oftheairsurroundingthepotatoesislessthan98
bullKeepstorewell-sealedtominimiseweightloss
bullPreventuncontrolledexternalairingressasthisusuallyhasalowerRHthanthestorageenvironment
Sugars
Sugarsincreaseandfrycolourswilldarkenifpotatoesarestoredatcoldtemperatures
bullStorecropsforprocessingatc7-10degC
bullMonitorcold-storedpre-packpotatoesforeffectsofsugarincreaseontaste
bullIfunsurecheckstoragerequirementswithyourcustomer
ACTION POINTS
CroPPHYSIoLoGY
14 S T O R E m a n a g E R S rsquo g U I D E
Silverscurf Blackdot Skinspot dryrot Gangrene Softrot
moderateinfection
severeinfection
4 Controlofstoragediseases
DiseasecontrolisafundamentalcomponentofstoragemanagementMostdiseasesdonotoriginateinstoretheycomefromtwoprimarysourcestheseedorthesoilHowevermanyofthediseaseproblemsaffectingthepremiummarketscandeveloptosomedegreeinstoreandifnotcontrolledtheconsequencescanbecatastrophiceitherintermsofphysicalbreakdownofthecroporinlossofmarketvalueWhetherdiseasewilldevelopinstoreornot(Figure41)dependson
bullTheamountofinoculumusuallysporesorbacteriapresentonthetubersbullWhethermoisturenutrientsandtemperaturearesuitableforthediseasetogrowbullThenaturalresistanceofthetubertothediseaseorganism
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
15S T O R E m a n a g E R S rsquo g U I D E
Storemanagementallowsustoinfluencethisrelationshipparticularlyinrelationtothemicro-climatearoundthetubertocontroldiseasesduringstorage
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
Micro-climate Tuberresistance
Inoculum
Figure 41 Interaction between micro-climate and disease
notifiablediseases
SomediseasesarenotindigenousinBritainandtheirestablishmentwouldaffectthelong-termviabilityofthepotatoindustryIfsymptomsofeitherbrownrotorringrotaresuspectedthenimmediatecontactwithlocalDEFRAofficesorPlantHealthandSeedinspectorateisnecessaryVisitwwwdefragovukplanthphhtmemailplanthealthinfodefragsigovukortelephone01904455174toreportsuspectedcasesinEnglandandWalesInScotlandvisitwwwsasagovukplant_health
PreventativemeasuresexistGotowwwpotatoorguksafehaventolearnmoreaboutnationalschemesthatprotectseedandwarecrophealth
ringrotBrownrot
16 S T O R E m a n a g E R S rsquo g U I D E
Figure 52 Ensure dust and debris are removed from ducts
CrosscontaminationofsporesbetweenpotatostocksisinevitableFanventilationwithinthestoremayincreasethespeedofthismovementcomparedwithnaturalconvectionButtheairflowisabenefitasithelpskeepthecropfreefromcondensationpreventinganysporeswhichdosettlefromgerminating
MajordustmovementanddispersaloccurswhenforklifttrucksstirupdustonthefloorduringhandlingTheresultantdustcloudwillsettleontopofthecropwherethecondensationneededforgerminationismostlikelyIfgradingiscarriedoutwithinthestorethiswillalsocreateaconsiderabledustcloudwithsimilarconsequences
dustremovalSweepingwithabrushmovestheheavierdustparticlesalongthefloorwhilecreatingacloudoflighterparticleswhichincludesthemajorityofsporesVacuumingloosensandremovesallfractionsofdustandiffittedwithafinefilterwillremovemostharmfulsporesfromthestoreVacuumingisthereforemuchpreferredtosweeping
disinfectionRemovingdustandsquashedtuberswillremovethemajorityofinoculumpresentSomedustandsporeswillremainonthefloorwallsandraftersaswellasthefloorandsidesofpotatoboxesthemajorityofwhichcanberemovedbypowerwashingIftotalremovalofviablesporesisrequiredegforhighhealthcropsadisinfectantcanbeusedThisisparticularlyrelevantinstoreswheredamagerelateddiseasessuchasdryrothaveoccurred
5 Storehygiene
AcleanstorefreefromdiscardedtubersdustanddebrishasanumberofadvantagesItwillminimisecropinfectionimproveairflowcontributetoworkerhealthandcomfortandislikelytoimpressclientsandcustomers
SomesoilisinevitablybroughtintostorewiththeharvestedcropOncedrythisbecomesapotentialsourceofdustwhenthecropismovedIfthecropisfreeofdiseasewhenharvestedanditremainssooverthestorageperiodthenthedustwillbemainlymineralinnatureHoweverifthecropisdiseasedorbecomessoduringstoragethedustmaycontainlargequantitiesofsporeswhichwillbeasourceofinoculuminthepresentorfutureyears
dustdispersalConvectioncurrentscausedbyrespirationheatfromthecropwillcirculatedustandsporesthroughoutthestore
Figure 51 Vacuuming of potato store
17S T O R E m a n a g E R S rsquo g U I D E
StorEHYGIEnE
Post-storagecleaning
bullStore-cleaningshouldbeundertakenannuallyInboxstoresthisisbestcarriedoutimmediatelyafterthelastcrophasbeenremovedsocleanedboxescanbereturnedtostore
bullInayearfollowingcropinfectionbysilverscurforskinspotextrarigorouscleaningshouldbecarriedout
bullVacuumdirtanddebrisfromfloorsledgesbeamsandotherhorizontalsurfaces
bullWhereinsulationisdamagedorisroughandcollectsdustrepairandvacuum
bullOnlypowerhoseifinsulationismoisture-proof
Cleaningboxes
bullEnsurethatbox-tippersongradinglinesaredesignedtodischargethetotalboxcontentstogetridofmajorcontamination
bullUsepowerhosetocleanboxes
bullWherecleaningboxesisroutineconsidersettingupaconveyor-basedautomaticwashingsystem
bullPower-washboxesforhighhealthcrops
bullWherepossiblereturncleanedboxestostoreorkeepundercoverasthiscanextendboxlifeby70
Whentousedisinfectants
Forhighhealthseedcropsdisinfectantsmaybebeneficialespeciallyafteracontaminatedcropinthepreviousyear
bullUsedisinfectantmistfogorsprayaftervacuumingstore
bullSpraydisinfectboxeswhichhelddiseasedcropout-gradesorlsquobrockrsquo
bullFollowinggradingofdiseasedpotatoespower-washgradinglinethenspraywithdisinfectantwheregradinghighhealthcrops
bullAlwaysuseapprovedproductsandseekspecialistadvice
notesomedisinfectantsmaydamagestoreinsulationandelectricalfittingsndashconsulttheproductlabelbeforeuse
dailycleaning
bullVacuumthefloorparticularlyforkliftroutesandundergradersatleastonceaday
Gradinginstore
GradinginstoreislikelytoincreasetheamountofcontaminateddustinthestoreandthelikelihoodofambientairenteringthroughopendoorsDustprovidesdiseaseinoculumwhileambientairmaycausecondensationparticularlyonthetopsurfaceofboxesorpile
bullIdeallygradeinseparatebuildingwithaplasticstripdoorbetweenthestoreandgradingarea
bullIfgradinginstoreisunavoidableenclosepickersinwarmedcabinandfitadustcontrolsystemtotheline
bullFitdewpointtemperaturemonitortowarnofcondensationrisks
ACTION POINTS
LeavingboxesoutsidewillallowlighttokillviablesporesBoxesshouldnotbestackedmorethanfourboxeshighforsafetyandifstackedinpairsasmallgapbetweenrowswillallownatural(ultraviolet)lighttoreachonesideofeveryboxHoweveroutsidestackingcanreduceboxlifebyupto40
CleaningandenergyefficiencyMaintainingfansventilationandrefrigerationequipmentinacleanconditionwillhelpprolongtheirworkinglifeand
improvetheirworkingefficiencyEnsurethattemperatureandhumidityprobesarekeptcleanandinspectlouvresevaporatorsandcondensersIfnecessarycleanbyvacuumingorpowerwashingIfwashingtakecarearoundelectricalandmovingsystemsandensurethatanyresultingiceisremovedbydefrosting
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
3S T O R E m a n a g E R S rsquo g U I D E 333
Introduction
thisisthesecondeditionofthePotatoCouncilrsquosStoreManagersrsquoGuideIthasbeenproducedtoofferacomprehensiveoverviewofbestpractice
inpotatostoremanagement
ManagementiskeyPotatostorageisacriticalcomponentofthepotatoproductionprocesswithsomecropsspendinglongerinstoragethantheydointhegroundItfollowsthereforethatpotatoesinstoresshouldbeaffordedasimilarlevelofmanagementinputasmightbeappliedtoagrowingcropThesituationinstoresisdynamicthecropisrespiringandreactingtoitsenvironmentStoreoperatorsmusthavethecapabilityndashinbothexpertiseandenvironmentalcontrolequipmentndashtorespondtothischangetooptimiseconditionsinthestoreandmaintainqualitythroughoutthestorageperiod
AcriticaltimeforpotatostorageMuchofthepotatostorageinGreatBritainhassufferedfromalengthyperiodwithoutmajorcapitalinvestmentManybusinessesnowfacecriticaldecisionsaboutthecontinuedsuitabilityofsomeolderstores
Thefirststeponthisdecision-makingpathisthestoreassessmentprocess(Section1)ThishelpstoidentifyanydeficienciesorareasforimprovementevaluationofperformanceprioritisationforoperationandsuitabilityforspecificusesHavingtherightequipmentforthejobisfundamentaltosuccessStorageisnotjustaboutkeepingpotatoesitisaboutmaintainingtheirqualitythroughoutthestorageperiodsothatitispossibletodeliverconsistentlyinaccordancewiththemarketspecificationataneconomicandsustainablecosttoearnaworthwhilereturn
ChangestoatrustedguideInupdatingthisguidethesametried-and-testedformathasbeenretainedandemphasishasbeenplacedonprovidingadvicewhichisapplicabletomoststorageinstallationsHowevertheopportunityhasalsobeentakentohighlightnewdevelopmentsandtechniqueswhichwillbeofinteresttothoselookingtomovetheirstorageforwardoverthecomingseasons
TopicswhichfeatureprominentlyinthePotatoCouncilrsquosresearchprioritiesincludebullDiseasemanagementbullChemicalresidueminimisationbullCostcontrolbullEnergyefficiencyandsustainability
Focusedissue-specificstrategieshavebeenintroducedandareanincreasinglyimportantaspectofpotatostoremanagementTheseincludebullThe Safe HavenschemeforthepreventionofnotifiablediseasesbullThePotato Industry CIPC Stewardship Action PlantoaddressallaspectsoftheuseofthesproutsuppressantPleaserefertowwwpotatoorgukcipcforthelatestinformation
FindingtheinformationyouneedTheguideiswritteninamodularformatwithcross-referencingsoyoucanmovebetweenthesectionswhicharerelevanttoyourstorageBestpracticeguidanceisbasedaroundinformationfromarangeofsourcessummarisedinthebibliography(Appendix1)
Muchoftheinformationisderivedfromlevy-fundedresearchanddevelopmentbutisalsosupportedbysomefromgovernmentindustryortheprivatesectorIfyouneedfurtherassistanceintheinterpretationoftheguidepleasecontacttheStorageAdviceLineon08000282111ore-mailsbcsrpotatoahdborguk
4 S T O R E m a n a g E R S rsquo g U I D E
Contents
IntroduCtIon 3
1 StorESELF-ASSESSMEnt 6 Aquickmethodofassessingastorersquoscapabilities
2 StorAGEBuILdInGS 10 Basicinformationontherequirementsforstoragebuildingsdiurnalvariation
3 CroPPHYSIoLoGY 12 Respirationdormancysugars
4 ControLoFStorAGEdISEASES 14 Whydiseasesdevelopinstoreintegratedcontrolcommonstoragediseases
5 StorEHYGIEnE 16 Keyrequirementsforminimisingdiseasecontaminationinstore
6 SErVICInGAndSEnSorS 18 Routinemaintenanceofequipmentandcalibrationofsensors
7 LoAdInGtHEStorE 20 Cropsamplingboxstackingspeedofloading
8 VEntILAtIon 22 Automationairflowratesspaceandpositivelyventilatedstores
9 drYInG 24 Removaloffreemoisturedryingfrontspositiveventilation
10 WoundHEALInGAndPuLL-doWn 26 Ratesofwoundhealingriskbasedmanagementtemperaturereduction
11 CondEnSAtIonontHECroP 28 Whycondensationonthecropoccursriskstothecrop
5S T O R E m a n a g E R S rsquo g U I D E
12 StruCturALCondEnSAtIon 30 Whystructuralcondensationoccurspreventativemeasuresroofspaceheating
13 rEFrIGErAtIon 32 Environmentalcontrolcoolingratesmaintenance
14 HuMIdItY 34 Humidityandmoisturelosshumidification
15 EnErGYMAnAGEMEnt 36 Monitoringexamplecostsoptimisinguse
16 StorEAtMoSPHErE 38 Oxygencarbondioxideothervolatiles
17 StorAGEForMArKEtS 40 CostscropmonitoringgettingthebestfromQCsampling
18 SProutSuPPrESSIon 44 RequirementforsproutcontrolactiveingredientsoptimisinguseofCIPC
19 WArMInG 46 Physicsofwarmingsystemstousedryingofskinsandlsquofingernailrsquodamage
20 StorEMonItorInGAndQuALItYASSurAnCE 48 Recordkeepingandprotocolsstoremonitoringanddatalogging
21 HEALtHAndSAFEtY 50 Workingatheightrisksinstoressafetyclothing
Appendices
1Bibliography 52
2Glossaryofterms 53
3Metricequivalents 54
4dew-pointtable 55
6 S T O R E m a n a g E R S rsquo g U I D E
1 Storeself-assessment
ForeachstorefeatureinthetableconsiderthefactorslistedandringthedescriptiononeachlinewhichbestsummarisesyourownstoreUsetheassessmenttoidentifythoseareaswhereimprovementscanbemade(anyscoring1asaminimum)andconsulttheappropriatesectionforfurtherinformationSomeproblemsmaybeeasytosolveandwillquicklyproducesignificantbenefitsothersmayneedlonger-termplanningtorectify
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
HYGIEnE
Cleaningfrequency
Mainmethodusedwhere
VErMInControL
HIGHrISKoFContAMInAtIonNocleaning
Sweeping
Nospecificmeasures
CleanedannuallyVacuumampdebrisremoval
Floorandwalls
Controlmeasuresinplacewithinstore
Vacuum+wash
+washboxesampmainsurfaces
VErYLoWdISEASErISKStorecleaneddaily+disinfectantapplied
+fogappliedtoentirestore
Accreditedprofessionalpestcontrolforfarm
Storehygiene
StruCturE
Storefabric
door(s)
Exposure
LEAKYPronEtoCondEnSAtIonLotoflightenters
2ormoregapsallround
Noshelter
Somelightenters
Door(s)sealedwithbrushesorrubber
Shelteredfromprevailingwind
Oddpinpricksoflight
Oneexternaldooronlysealedallround
Shelteredallround
SEALEdControLLABLECompletelydark
Noexternaldoorsloadviagradingarea
Singledoorexitstogradingarea
Storagebuildingsampcondensationonthecrop
InSuLAtIon
roof
Wall
noInSuLAtIon
Singleskinroof
Brickblockstonewalls
Doubleskin+glassfibreroof
Lightweightcavitywalls
lt75mmEEPsprayfoam
Compositepanel+gt50mmfoamEEP
HIGHLEVELInSuLAtIon75mm+foamEEPinsulation
Ascolumn3butgt75mm
Storagebuildings
7S T O R E m a n a g E R S rsquo g U I D E
bullringthedescriptionswhichmostcloselydescribeyourstorebullConsiderthefactorsandrisksthisself-assessmentidentifiesbulldecideonanyactionneededbullrefertotheappropriatesectionoftheguideorseekfurtherspecialistadvice
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
VEntILAtIon
Bulkstoresystem
Boxstoresystem
Boxstoreairdistribution
recirculation
HIGHrISKoFContAMInAtIonNofanopendooronly
Nofanopendooronly
Aroundboxesnosingleldquoairrollrdquoestablished
None
Fanslt002m3st
Fanslt002m3st
Spaceventilationformsrollofairpartviaboxapertures
Someairmovementbutnoairroll
Spaceventilationampfansge002m3st
Ascolumn2+rooffansorpositiveventilationwithtraditionalboxes
Intermittentlt002m3stLowratepartstore
PoSItIVEampFAStdrYInGFansge002m3st
Positiveventilationampfansge004m3st
Positiveventilationusingpurposedesignedboxes
Intermittentge002m3stLowratecontinuous
Ventilation
FAnSYStEMS
Fantype
Fanefficiency
Ventilationcontrol
Mixing
Inletairprotection
unControLLEdrISKtoCroP
Centrifugalfan
Oldagedfanwithbigstartingload
Onoffswitching
Manual
Nofrostthermostat
Axial(propellerstyle)
Modernfan(s)withpower-factorcorrection
Automaticswitchingofsinglemultiplefans
Autonoairmixing
Thermostattocutfanoffineventoffrost
Automatedaxialfans
High-efficiencyfansforlowrunningcost
Manualspeedcontrolofautomaticsinglemultiplefans
Auto+airmixing
Inlettemperaturecontrol
FuLLControLoFCooLInG
AxialfansforpositiveventilationSoftstarthigh-efficiencylownoisefans
Automatedvariablespeedcontroloffans
Auto+airmixingampdew-pointcontrol
Inlettemperature+condensationcontrol
Ventilation
8 S T O R E m a n a g E R S rsquo g U I D E
1 Storeself-assessment
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
BoXStACKInG
Spaceventilatedstores
Cross-stackedboxes(ieat90degtomainblock)
Boxheight
rEStrICtEdAIrFLoWrISKoFCondEnSAtIonBoxesstackedrandomly
Boxesstackedacrosspalletslotsofmainblock
Inconsistentstackingheightthroughoutstore
Gapsacrossstore(riskofshortcircuiting)
Boxescross-stackedawayfrommainblocktoallowairtoenterpalletapertures
Rowsateaves1boxlowercapacityeconomicsdictate
Gapsgt150mmbetweenrows
Slattedboxeslessrestrictivetoairflowwhencross-stackedifonly2wide
Allboxesatsameheight
oPtIMALAIrFLoWLoWrISKoFCondEnSAtIonGapslt150mmandsupplementaryfanstotargetlsquodeadspotsrsquo
Boxesstackedat90degtoairflowwith50mmgapsbetweenalternateboxeswithinrows
Allboxesatsameheightroofspaceventilatedheated
Loadingthestore
rEFrIGErAtIon
Fridgesystemsizeampperformance
Spaceventilationcoolingrate
Positiveventilationcoolingrate
dEHYdrAtIonrISK
Smallfridgecoilwithair-onair-offtempdifferencegt35degC
Longrunningtimesnoeffectivecooling
Asabove
Coolsatlt025degCday
Coolsatlt05degCday
Coolsatgt05degCday
Coolsatgt1degCday(ManagecondensationriskP11)
FrIdGESIZEoPtIMAL
Air-onair-offtemperaturedifference~25degC
Coolsat~05degCday
Coolsat~1degCday
Refrigeration
9S T O R E m a n a g E R S rsquo g U I D E
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
MonItorInGAndtrACEABILtY
temperaturesensors
Bulkstacksensorplacement
Condensationcontrol
Stockcontrol
Storerecording
LACKoFControL
Nosensorsinstore
Asabove
Asabove
Chemicalrecordsonlylegalminimum
Asabove
Inaironlycropconditionunknown
Topsurfaceonly-pronetoinfluencebyairabove
Controloftemperaturedifferentials
Chemicaluseplusstocklocationinstorerecorded
Occasionalmanualrecordingofstoretemperatures
1or2sensorsincropnomeasureoftemperaturevariation
Topandbaseofstacktomeasurepiletemperaturegradient
Relativehumiditymeasurementfordew-pointcontrol
Chemicalusestockdetailslabelledoneachbox
Regularmanualrecordingofstoretemperaturesandfanrunningtimes
FuLLCAPABILItY
1sensorper100tonnes
Ascolumn3butalso300mmdowntoanticipatecondensation
Skinresistancesensingtomeasureanywetting
Boxrecordsincludelocation-feedbackonstorageproblems
Automaticloggingofstoretemperaturesandfanrunningtimes
LoadingthestoreampStoremonitoringandqualityassurance
QCSAMPLInG Singlepointsampling Multi-pointsampling
ononelevelMulti-pointsamplingonmorethanonelevel
Comprehensivesamplingthroughoutthestore
Storageformarkets
SEEdGrAdInG
CondEnSAtIonrISK
Instore Nextdoorbutnoairlock
Nextdoorwithstripcurtain
StorEISoLAtEd
Nextdoorwithhighspeeddoor
Condensationonthecrop
10 S T O R E m a n a g E R S rsquo g U I D E
Fabricordoorleakagetowind-inducedventilationreducesthebenefitsofthestoreasitislikelytoleadtolossofenvironmentalcontrolcropweightlossandpossiblecondensationonthecropVentilationorrefrigerationrun-timewillincreasetocoolthecropwarmedbytheleakingair
ContainmentThecapitalcostofabulkstorewithload-bearinginsulatedretainingwallsishigherthanforaboxstoreButwhenthecapitalcostofboxesisaddedbulkstorageischeaperoverallBoxstoreseaseseparationfordifferentstocksandprovidemoreflexibilityforcropmovementandmarketingDeepbulkpilescanleadtopressurebruisingproblemsifthecropisstoredover40mhighorifexcessivelyventilatedbynon-humidifiedairBoxstorageisnormallyfreefrompressurebruisinganddependingontheirqualityboxescanbestackedupto8high
InsulationThequalityoftheinsulationwilldeterminetoalargeextenthowwellapotatostoreperformsInsulationisakeyfactorforapotatostoremuchmoresothanitisforgeneralpurposebuildings
MaintainingtemperaturesabovefreezingpointisseldomaproblemgiventhequantityofheatproducedinalargestoreHoweveranyheatthatleaksintoastorehastoberemovedbyexpendingenergyeitherintheformofventilationorrefrigerationInadditiontotheimplicationsoncosttheavoidableoperationofenvironmentalcontrol
2 Storagebuildings
Awellsealedandinsulatedpotatostore(Figure21)will
bullAllowthecroptobekeptatastabletemperaturelargelyunaffectedbydiurnalvariationandambientconditions
bullHelpmaintainarelativehumidityof90-100tominimisetuberweightloss
bullAllowcropstobestoredfreefromcondensationinchangeableweatherconditions
ControlledventilationControlledventilationallowscroprespirationheattoberemovedandthecroptobedriedandcooledFansarepositionedtocreateaflowofairthroughthecrop(positiveventilationbulkorbox)ortoformarollingmassofairthatwillflowoverthestackofboxesandthroughtheirpalletslots(spaceventilation)
Coolingcanbeachievedusingambientairandormechanicalcooling(refrigeration)Internalrecirculationofair(withoutcooling)canbeusedtoeliminatetemperaturevariationortodistributechemicalsforsproutsuppressionordiseasecontrol
AirflowshouldbeasuniformaspossiblethroughoutthestoretogiveevendryingandstablecroptemperaturesAwelldesignedstorewillhavebeenbalancedtoachieveuniformityofairflowatitstypicaloperatingconditionThismightincludefeaturessuchastaperedairductsorgraduatedlateraloutletstodeliversimilarquantitiesofairacrossthewholestore
Figure 21 A well sealed and insulated potato store
11S T O R E m a n a g E R S rsquo g U I D E
foundinpotatostoreswherecompositemetalpolyisocyanurate(PIR)sandwichpanelsareusedThesearecommonplacenowadaysfornewlybuiltstoresOthersystemsforupgradesofferatbestlittlemorethanavapourcheckThistendstolimitthechoiceofinsulationtoeithersprayorboardpolyurethaneoralternativelyexpandedextrudedpolystyreneboard
Specialistadviceshouldbesoughtforallaspectsofstoragebuildingdesign
equipmentwillalwaysincreasewaterlossfromthecropItisthereforejustasbeneficialtouseinsulationtolimitanyheatingressintothestoreasitistominimisetheeffectsofcoldweatherAlight-colouredreflectiveexternalsurfacewillreduceunwantedsolarradiationgains
NearlyallinsulationmaterialshavetheirperformancereducedsignificantlybyverysmallincreasesintheirmoisturecontentTheuseofvapourbarrierstoprotectinsulationisonlyeffectiveinthehighhumidityconditions
Storeassessment
bullUndertakeadetailedassessmentofyourstoreasdescribedinsection1
Balancedventilation
bullTheventilationsysteminastoreshouldbeinbalanceThismeansthatforoptimalperformancedesignfeaturesarerequiredndashegtaperedductsndashtooffsettheeffectsofpressuredropintheventilationsystemP8
doorsandlouvres
bullDoorsandlouvresaretheweakpointsoftheinsulationlsquoenvelopersquoMakesuretheycloseproperlyandstayclosedRegularpositiveactuationfromacontrollerisbeneficialforkeepingambientlouverswhicharesubjecttowindpressureclosed
Insulation
bullEnsurestoreinsulationisingoodconditionandeffective
bullWatchforsignsofcondensationwithinthestructurethatwilldegradetheinsulationvalueegdelaminatedinsulationboardswheremoisturehasgotinbehindthepanels
bullEnsureanynewbuildwithcompositeconstructionusesPIRpanelswhichareresistanttospreadofflameinthecoreintheeventoffire
ACTION POINTS
StorAGEBuILdInGS
Figure 22 Building envelope stabilises internal climate
12 S T O R E m a n a g E R S rsquo g U I D E
AllotherthingsbeingequalmoisturelossisafunctionofstorehumidityandairflowratePotatostoreswillusuallysettletoapproximately98relativehumidityandintheabsenceofahumidificationsystemthiswillbederivedbyevaporationofmoisturefromtubersInappropriatelyspecifiedrefrigerationunitscanexacerbatemoistureloss
dormancyFreshlyharvestedtubersusuallydonotsproutevenwhenconditionsareoptimalforsproutgrowthTheperiodoverwhichsproutgrowthisinhibitedbytuberphysiologyratherthanenvironmentalreasonsistermedthedormantperiodorsimplylsquodormancyrsquo
LargedifferencesindormancyoccurbetweenvarietiesWarmstoragetemperatureshaveadormancy-breakingeffectSelectionofvarietiesbydormancycharacteristicscanbeusefulforminimisingsprout-suppressantinputs
Dormancybreakistakenasthepointwhere50oftubershavesproutsof3mmormoreinlengthWarmdrysummerstendtoreducedormancy(inextremecasesleadingtosproutgrowthinthefieldbeforeharvest)whilecoolgrowingconditionswillgenerallyprolongitWaterlogginghasadormancy-breakingeffect
Woundhealing(curing)Wheretubershavebeensubjectedtowounding(egbyhandlingduringharvest)thetuberwillattempttohealthewoundndashaprocessinvolvingsuberisationandcell-divisionThespeedofthisprocesswhichisimportantforpreventingmoisturelossanddiseaseingressisaffectedbyanumberoffactorsTheseincludestoragetemperatureandhumiditywithwarmertemperaturesandhigherhumidityreducingthetimerequiredforwound-healing
Althougheffectivewound-healingisimportantconditionsthatareoptimalforcuringmayalsobesuitablefordiseasedevelopmentWherecropsareharvestedearlyundergoodconditionsorwherethestoragedurationislimitedsufficientcuringmayoccurduringtheperiodoverwhichcroptemperatureisreducedtotheholdingvalueP11
3 Cropphysiology
respirationPotatotubersarelivingorganismsandinstorecontinuetorespireandrespondtotheirenvironmentTheydosobyusingsugarsfromstarchinrespirationThisprocessconsumesoxygenandreleasescarbondioxideandsomeheatenergywhichimpactonstoragesystems
Respirationishighestatharvestandfallsrapidlytoabasallevelinthefirstweeksofstorage(Figure31)Respirationisgreaterinearly-liftedimmaturecropsthaninlate-liftedmaturecrops
Basalrespirationratedependspredominantlyonstoragetemperature(Figure32)Minimumrespirationrateisachievedataround5oCwiththerateincreasingaboveorbelowthistemperature
Handlingmechanicaldamageexposuretoethyleneandsproutingwillleadtoanincreaseinrespirationrate
EvaporationAlthoughsomemoistureislostintheprocessofrespirationmostislostbysimpleevaporationfromthetubersurfaceEffectivewound-healingandsproutcontrolisimportantinlimitingmoisturelossfromtubers
Figure 31 Respiration after lifting ndash early harvest
Figure 33 Moisture exchange between tuber skin and surrounding air in balance at ~98 relative humidity
Figure 32 Respiration in relation to storage temperature
1 2 3 4 5 6 7 8 9 10
Hea
t out
put (
Wto
nne)
35
0
5
10
15
20
25
30
Harvest date 9 September
Days after harvest
Harvest date 20 October
5 15 25
Rat
e of
resp
iratio
n (m
g C
O2k
ghr
)
12
0
2
4
6
8
10
Storage temperature (˚C)
13S T O R E m a n a g E R S rsquo g U I D E
ThisisaccomplishedsimplybyincreasingstoragetemperatureHoweverreconditioningleadstovariabilityinfrycolourandisthereforenotrecommendedasaroutinestoragepractice
PreconditioningmayalsobeusedtomaintainprocessingqualityHeretherearenodistinctcuringpull-downholdingperiodsandfrycolourorsugarcontentisusedtodeterminecropstoragetemperatureTemperaturereductiontoatargetholdingvalueonlyoccursprovidinggoodprocessingqualityismaintained
GreeningandglycoalkaloidsTubersexposedtolightwillturngreenwhichresultsfromthesynthesisofchlorophyllChlorophyllisitselfharmlessbutgreentubersaregenerallyrejectedbecausetheyhaveelevatedlevelsofglycoalkaloidsagroupofnaturaltoxicantspresentinpotatoes
TopreventgreeninginstorageexposuretolightshouldthereforebeminimisedalthoughtheneedtoseethecropclearlyandhealthandsafetyrequirementsP21willoverridethisduringloadingandsubsequentshortperiodswhenstoresareaccessedtobeinspectedorsampled
SugarsandconditioningPotatoescontainthreemainsugarsglucoseandfructose(monosaccharides)andsucrose(adisaccharide)AllthreesugarsaresweetandareimportantflavourcomponentsinwarepotatoesInpotatoesforprocessingthestoremanagerisprimarilyinterestedinthemonosaccharidesDuringprocessingthesereactwithothercomponentstoproducethebrowningwhichisassessedbymarketsasfrycolourAstoremanagersupplyingcropforprocessingmayalsobeinterestedinsucrosecontentAlthoughsucrosedoesnottakepartinbrowningreactionstrendsinsucroselevelsmaybeusedtohelpensurelowreducingsugarsandlightfrycolourduringstorage
VarietygrowthstageandstoragetemperatureareimportantindeterminingtubersugarcontentPotatoesexhibitlowtemperature-sweeteningwheresugarsaccumulatewithinthetuberastemperatureisreducedDuringstorageforprocessingtemperatureshouldthereforebemaintainedatthelowestlevelthatsafelymaintainsacceptablefrycolour
Forprocessingcropschangesinsugarcontent(andhencefrycolour)canbeachievedusingreconditioning
respiration
Thegreatertherespirationrateofthepotatoesthemorelikelyitisthatwarmairwillcondenseoncoolersurfacepotatoes
bullPositivelyventilatepotatoestoremoverespirationheattopreventsurfacecondensation
bullUsehighventilationratestopreventcondensationinheavilyrespiringearly-liftedorimmaturecropsP11
Evaporation
Moisturelossfrompotatoesduetoevaporationwilloccuriftherelativehumidity(RH)oftheairsurroundingthepotatoesislessthan98
bullKeepstorewell-sealedtominimiseweightloss
bullPreventuncontrolledexternalairingressasthisusuallyhasalowerRHthanthestorageenvironment
Sugars
Sugarsincreaseandfrycolourswilldarkenifpotatoesarestoredatcoldtemperatures
bullStorecropsforprocessingatc7-10degC
bullMonitorcold-storedpre-packpotatoesforeffectsofsugarincreaseontaste
bullIfunsurecheckstoragerequirementswithyourcustomer
ACTION POINTS
CroPPHYSIoLoGY
14 S T O R E m a n a g E R S rsquo g U I D E
Silverscurf Blackdot Skinspot dryrot Gangrene Softrot
moderateinfection
severeinfection
4 Controlofstoragediseases
DiseasecontrolisafundamentalcomponentofstoragemanagementMostdiseasesdonotoriginateinstoretheycomefromtwoprimarysourcestheseedorthesoilHowevermanyofthediseaseproblemsaffectingthepremiummarketscandeveloptosomedegreeinstoreandifnotcontrolledtheconsequencescanbecatastrophiceitherintermsofphysicalbreakdownofthecroporinlossofmarketvalueWhetherdiseasewilldevelopinstoreornot(Figure41)dependson
bullTheamountofinoculumusuallysporesorbacteriapresentonthetubersbullWhethermoisturenutrientsandtemperaturearesuitableforthediseasetogrowbullThenaturalresistanceofthetubertothediseaseorganism
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
15S T O R E m a n a g E R S rsquo g U I D E
Storemanagementallowsustoinfluencethisrelationshipparticularlyinrelationtothemicro-climatearoundthetubertocontroldiseasesduringstorage
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
Micro-climate Tuberresistance
Inoculum
Figure 41 Interaction between micro-climate and disease
notifiablediseases
SomediseasesarenotindigenousinBritainandtheirestablishmentwouldaffectthelong-termviabilityofthepotatoindustryIfsymptomsofeitherbrownrotorringrotaresuspectedthenimmediatecontactwithlocalDEFRAofficesorPlantHealthandSeedinspectorateisnecessaryVisitwwwdefragovukplanthphhtmemailplanthealthinfodefragsigovukortelephone01904455174toreportsuspectedcasesinEnglandandWalesInScotlandvisitwwwsasagovukplant_health
PreventativemeasuresexistGotowwwpotatoorguksafehaventolearnmoreaboutnationalschemesthatprotectseedandwarecrophealth
ringrotBrownrot
16 S T O R E m a n a g E R S rsquo g U I D E
Figure 52 Ensure dust and debris are removed from ducts
CrosscontaminationofsporesbetweenpotatostocksisinevitableFanventilationwithinthestoremayincreasethespeedofthismovementcomparedwithnaturalconvectionButtheairflowisabenefitasithelpskeepthecropfreefromcondensationpreventinganysporeswhichdosettlefromgerminating
MajordustmovementanddispersaloccurswhenforklifttrucksstirupdustonthefloorduringhandlingTheresultantdustcloudwillsettleontopofthecropwherethecondensationneededforgerminationismostlikelyIfgradingiscarriedoutwithinthestorethiswillalsocreateaconsiderabledustcloudwithsimilarconsequences
dustremovalSweepingwithabrushmovestheheavierdustparticlesalongthefloorwhilecreatingacloudoflighterparticleswhichincludesthemajorityofsporesVacuumingloosensandremovesallfractionsofdustandiffittedwithafinefilterwillremovemostharmfulsporesfromthestoreVacuumingisthereforemuchpreferredtosweeping
disinfectionRemovingdustandsquashedtuberswillremovethemajorityofinoculumpresentSomedustandsporeswillremainonthefloorwallsandraftersaswellasthefloorandsidesofpotatoboxesthemajorityofwhichcanberemovedbypowerwashingIftotalremovalofviablesporesisrequiredegforhighhealthcropsadisinfectantcanbeusedThisisparticularlyrelevantinstoreswheredamagerelateddiseasessuchasdryrothaveoccurred
5 Storehygiene
AcleanstorefreefromdiscardedtubersdustanddebrishasanumberofadvantagesItwillminimisecropinfectionimproveairflowcontributetoworkerhealthandcomfortandislikelytoimpressclientsandcustomers
SomesoilisinevitablybroughtintostorewiththeharvestedcropOncedrythisbecomesapotentialsourceofdustwhenthecropismovedIfthecropisfreeofdiseasewhenharvestedanditremainssooverthestorageperiodthenthedustwillbemainlymineralinnatureHoweverifthecropisdiseasedorbecomessoduringstoragethedustmaycontainlargequantitiesofsporeswhichwillbeasourceofinoculuminthepresentorfutureyears
dustdispersalConvectioncurrentscausedbyrespirationheatfromthecropwillcirculatedustandsporesthroughoutthestore
Figure 51 Vacuuming of potato store
17S T O R E m a n a g E R S rsquo g U I D E
StorEHYGIEnE
Post-storagecleaning
bullStore-cleaningshouldbeundertakenannuallyInboxstoresthisisbestcarriedoutimmediatelyafterthelastcrophasbeenremovedsocleanedboxescanbereturnedtostore
bullInayearfollowingcropinfectionbysilverscurforskinspotextrarigorouscleaningshouldbecarriedout
bullVacuumdirtanddebrisfromfloorsledgesbeamsandotherhorizontalsurfaces
bullWhereinsulationisdamagedorisroughandcollectsdustrepairandvacuum
bullOnlypowerhoseifinsulationismoisture-proof
Cleaningboxes
bullEnsurethatbox-tippersongradinglinesaredesignedtodischargethetotalboxcontentstogetridofmajorcontamination
bullUsepowerhosetocleanboxes
bullWherecleaningboxesisroutineconsidersettingupaconveyor-basedautomaticwashingsystem
bullPower-washboxesforhighhealthcrops
bullWherepossiblereturncleanedboxestostoreorkeepundercoverasthiscanextendboxlifeby70
Whentousedisinfectants
Forhighhealthseedcropsdisinfectantsmaybebeneficialespeciallyafteracontaminatedcropinthepreviousyear
bullUsedisinfectantmistfogorsprayaftervacuumingstore
bullSpraydisinfectboxeswhichhelddiseasedcropout-gradesorlsquobrockrsquo
bullFollowinggradingofdiseasedpotatoespower-washgradinglinethenspraywithdisinfectantwheregradinghighhealthcrops
bullAlwaysuseapprovedproductsandseekspecialistadvice
notesomedisinfectantsmaydamagestoreinsulationandelectricalfittingsndashconsulttheproductlabelbeforeuse
dailycleaning
bullVacuumthefloorparticularlyforkliftroutesandundergradersatleastonceaday
Gradinginstore
GradinginstoreislikelytoincreasetheamountofcontaminateddustinthestoreandthelikelihoodofambientairenteringthroughopendoorsDustprovidesdiseaseinoculumwhileambientairmaycausecondensationparticularlyonthetopsurfaceofboxesorpile
bullIdeallygradeinseparatebuildingwithaplasticstripdoorbetweenthestoreandgradingarea
bullIfgradinginstoreisunavoidableenclosepickersinwarmedcabinandfitadustcontrolsystemtotheline
bullFitdewpointtemperaturemonitortowarnofcondensationrisks
ACTION POINTS
LeavingboxesoutsidewillallowlighttokillviablesporesBoxesshouldnotbestackedmorethanfourboxeshighforsafetyandifstackedinpairsasmallgapbetweenrowswillallownatural(ultraviolet)lighttoreachonesideofeveryboxHoweveroutsidestackingcanreduceboxlifebyupto40
CleaningandenergyefficiencyMaintainingfansventilationandrefrigerationequipmentinacleanconditionwillhelpprolongtheirworkinglifeand
improvetheirworkingefficiencyEnsurethattemperatureandhumidityprobesarekeptcleanandinspectlouvresevaporatorsandcondensersIfnecessarycleanbyvacuumingorpowerwashingIfwashingtakecarearoundelectricalandmovingsystemsandensurethatanyresultingiceisremovedbydefrosting
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
4 S T O R E m a n a g E R S rsquo g U I D E
Contents
IntroduCtIon 3
1 StorESELF-ASSESSMEnt 6 Aquickmethodofassessingastorersquoscapabilities
2 StorAGEBuILdInGS 10 Basicinformationontherequirementsforstoragebuildingsdiurnalvariation
3 CroPPHYSIoLoGY 12 Respirationdormancysugars
4 ControLoFStorAGEdISEASES 14 Whydiseasesdevelopinstoreintegratedcontrolcommonstoragediseases
5 StorEHYGIEnE 16 Keyrequirementsforminimisingdiseasecontaminationinstore
6 SErVICInGAndSEnSorS 18 Routinemaintenanceofequipmentandcalibrationofsensors
7 LoAdInGtHEStorE 20 Cropsamplingboxstackingspeedofloading
8 VEntILAtIon 22 Automationairflowratesspaceandpositivelyventilatedstores
9 drYInG 24 Removaloffreemoisturedryingfrontspositiveventilation
10 WoundHEALInGAndPuLL-doWn 26 Ratesofwoundhealingriskbasedmanagementtemperaturereduction
11 CondEnSAtIonontHECroP 28 Whycondensationonthecropoccursriskstothecrop
5S T O R E m a n a g E R S rsquo g U I D E
12 StruCturALCondEnSAtIon 30 Whystructuralcondensationoccurspreventativemeasuresroofspaceheating
13 rEFrIGErAtIon 32 Environmentalcontrolcoolingratesmaintenance
14 HuMIdItY 34 Humidityandmoisturelosshumidification
15 EnErGYMAnAGEMEnt 36 Monitoringexamplecostsoptimisinguse
16 StorEAtMoSPHErE 38 Oxygencarbondioxideothervolatiles
17 StorAGEForMArKEtS 40 CostscropmonitoringgettingthebestfromQCsampling
18 SProutSuPPrESSIon 44 RequirementforsproutcontrolactiveingredientsoptimisinguseofCIPC
19 WArMInG 46 Physicsofwarmingsystemstousedryingofskinsandlsquofingernailrsquodamage
20 StorEMonItorInGAndQuALItYASSurAnCE 48 Recordkeepingandprotocolsstoremonitoringanddatalogging
21 HEALtHAndSAFEtY 50 Workingatheightrisksinstoressafetyclothing
Appendices
1Bibliography 52
2Glossaryofterms 53
3Metricequivalents 54
4dew-pointtable 55
6 S T O R E m a n a g E R S rsquo g U I D E
1 Storeself-assessment
ForeachstorefeatureinthetableconsiderthefactorslistedandringthedescriptiononeachlinewhichbestsummarisesyourownstoreUsetheassessmenttoidentifythoseareaswhereimprovementscanbemade(anyscoring1asaminimum)andconsulttheappropriatesectionforfurtherinformationSomeproblemsmaybeeasytosolveandwillquicklyproducesignificantbenefitsothersmayneedlonger-termplanningtorectify
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
HYGIEnE
Cleaningfrequency
Mainmethodusedwhere
VErMInControL
HIGHrISKoFContAMInAtIonNocleaning
Sweeping
Nospecificmeasures
CleanedannuallyVacuumampdebrisremoval
Floorandwalls
Controlmeasuresinplacewithinstore
Vacuum+wash
+washboxesampmainsurfaces
VErYLoWdISEASErISKStorecleaneddaily+disinfectantapplied
+fogappliedtoentirestore
Accreditedprofessionalpestcontrolforfarm
Storehygiene
StruCturE
Storefabric
door(s)
Exposure
LEAKYPronEtoCondEnSAtIonLotoflightenters
2ormoregapsallround
Noshelter
Somelightenters
Door(s)sealedwithbrushesorrubber
Shelteredfromprevailingwind
Oddpinpricksoflight
Oneexternaldooronlysealedallround
Shelteredallround
SEALEdControLLABLECompletelydark
Noexternaldoorsloadviagradingarea
Singledoorexitstogradingarea
Storagebuildingsampcondensationonthecrop
InSuLAtIon
roof
Wall
noInSuLAtIon
Singleskinroof
Brickblockstonewalls
Doubleskin+glassfibreroof
Lightweightcavitywalls
lt75mmEEPsprayfoam
Compositepanel+gt50mmfoamEEP
HIGHLEVELInSuLAtIon75mm+foamEEPinsulation
Ascolumn3butgt75mm
Storagebuildings
7S T O R E m a n a g E R S rsquo g U I D E
bullringthedescriptionswhichmostcloselydescribeyourstorebullConsiderthefactorsandrisksthisself-assessmentidentifiesbulldecideonanyactionneededbullrefertotheappropriatesectionoftheguideorseekfurtherspecialistadvice
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
VEntILAtIon
Bulkstoresystem
Boxstoresystem
Boxstoreairdistribution
recirculation
HIGHrISKoFContAMInAtIonNofanopendooronly
Nofanopendooronly
Aroundboxesnosingleldquoairrollrdquoestablished
None
Fanslt002m3st
Fanslt002m3st
Spaceventilationformsrollofairpartviaboxapertures
Someairmovementbutnoairroll
Spaceventilationampfansge002m3st
Ascolumn2+rooffansorpositiveventilationwithtraditionalboxes
Intermittentlt002m3stLowratepartstore
PoSItIVEampFAStdrYInGFansge002m3st
Positiveventilationampfansge004m3st
Positiveventilationusingpurposedesignedboxes
Intermittentge002m3stLowratecontinuous
Ventilation
FAnSYStEMS
Fantype
Fanefficiency
Ventilationcontrol
Mixing
Inletairprotection
unControLLEdrISKtoCroP
Centrifugalfan
Oldagedfanwithbigstartingload
Onoffswitching
Manual
Nofrostthermostat
Axial(propellerstyle)
Modernfan(s)withpower-factorcorrection
Automaticswitchingofsinglemultiplefans
Autonoairmixing
Thermostattocutfanoffineventoffrost
Automatedaxialfans
High-efficiencyfansforlowrunningcost
Manualspeedcontrolofautomaticsinglemultiplefans
Auto+airmixing
Inlettemperaturecontrol
FuLLControLoFCooLInG
AxialfansforpositiveventilationSoftstarthigh-efficiencylownoisefans
Automatedvariablespeedcontroloffans
Auto+airmixingampdew-pointcontrol
Inlettemperature+condensationcontrol
Ventilation
8 S T O R E m a n a g E R S rsquo g U I D E
1 Storeself-assessment
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
BoXStACKInG
Spaceventilatedstores
Cross-stackedboxes(ieat90degtomainblock)
Boxheight
rEStrICtEdAIrFLoWrISKoFCondEnSAtIonBoxesstackedrandomly
Boxesstackedacrosspalletslotsofmainblock
Inconsistentstackingheightthroughoutstore
Gapsacrossstore(riskofshortcircuiting)
Boxescross-stackedawayfrommainblocktoallowairtoenterpalletapertures
Rowsateaves1boxlowercapacityeconomicsdictate
Gapsgt150mmbetweenrows
Slattedboxeslessrestrictivetoairflowwhencross-stackedifonly2wide
Allboxesatsameheight
oPtIMALAIrFLoWLoWrISKoFCondEnSAtIonGapslt150mmandsupplementaryfanstotargetlsquodeadspotsrsquo
Boxesstackedat90degtoairflowwith50mmgapsbetweenalternateboxeswithinrows
Allboxesatsameheightroofspaceventilatedheated
Loadingthestore
rEFrIGErAtIon
Fridgesystemsizeampperformance
Spaceventilationcoolingrate
Positiveventilationcoolingrate
dEHYdrAtIonrISK
Smallfridgecoilwithair-onair-offtempdifferencegt35degC
Longrunningtimesnoeffectivecooling
Asabove
Coolsatlt025degCday
Coolsatlt05degCday
Coolsatgt05degCday
Coolsatgt1degCday(ManagecondensationriskP11)
FrIdGESIZEoPtIMAL
Air-onair-offtemperaturedifference~25degC
Coolsat~05degCday
Coolsat~1degCday
Refrigeration
9S T O R E m a n a g E R S rsquo g U I D E
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
MonItorInGAndtrACEABILtY
temperaturesensors
Bulkstacksensorplacement
Condensationcontrol
Stockcontrol
Storerecording
LACKoFControL
Nosensorsinstore
Asabove
Asabove
Chemicalrecordsonlylegalminimum
Asabove
Inaironlycropconditionunknown
Topsurfaceonly-pronetoinfluencebyairabove
Controloftemperaturedifferentials
Chemicaluseplusstocklocationinstorerecorded
Occasionalmanualrecordingofstoretemperatures
1or2sensorsincropnomeasureoftemperaturevariation
Topandbaseofstacktomeasurepiletemperaturegradient
Relativehumiditymeasurementfordew-pointcontrol
Chemicalusestockdetailslabelledoneachbox
Regularmanualrecordingofstoretemperaturesandfanrunningtimes
FuLLCAPABILItY
1sensorper100tonnes
Ascolumn3butalso300mmdowntoanticipatecondensation
Skinresistancesensingtomeasureanywetting
Boxrecordsincludelocation-feedbackonstorageproblems
Automaticloggingofstoretemperaturesandfanrunningtimes
LoadingthestoreampStoremonitoringandqualityassurance
QCSAMPLInG Singlepointsampling Multi-pointsampling
ononelevelMulti-pointsamplingonmorethanonelevel
Comprehensivesamplingthroughoutthestore
Storageformarkets
SEEdGrAdInG
CondEnSAtIonrISK
Instore Nextdoorbutnoairlock
Nextdoorwithstripcurtain
StorEISoLAtEd
Nextdoorwithhighspeeddoor
Condensationonthecrop
10 S T O R E m a n a g E R S rsquo g U I D E
Fabricordoorleakagetowind-inducedventilationreducesthebenefitsofthestoreasitislikelytoleadtolossofenvironmentalcontrolcropweightlossandpossiblecondensationonthecropVentilationorrefrigerationrun-timewillincreasetocoolthecropwarmedbytheleakingair
ContainmentThecapitalcostofabulkstorewithload-bearinginsulatedretainingwallsishigherthanforaboxstoreButwhenthecapitalcostofboxesisaddedbulkstorageischeaperoverallBoxstoreseaseseparationfordifferentstocksandprovidemoreflexibilityforcropmovementandmarketingDeepbulkpilescanleadtopressurebruisingproblemsifthecropisstoredover40mhighorifexcessivelyventilatedbynon-humidifiedairBoxstorageisnormallyfreefrompressurebruisinganddependingontheirqualityboxescanbestackedupto8high
InsulationThequalityoftheinsulationwilldeterminetoalargeextenthowwellapotatostoreperformsInsulationisakeyfactorforapotatostoremuchmoresothanitisforgeneralpurposebuildings
MaintainingtemperaturesabovefreezingpointisseldomaproblemgiventhequantityofheatproducedinalargestoreHoweveranyheatthatleaksintoastorehastoberemovedbyexpendingenergyeitherintheformofventilationorrefrigerationInadditiontotheimplicationsoncosttheavoidableoperationofenvironmentalcontrol
2 Storagebuildings
Awellsealedandinsulatedpotatostore(Figure21)will
bullAllowthecroptobekeptatastabletemperaturelargelyunaffectedbydiurnalvariationandambientconditions
bullHelpmaintainarelativehumidityof90-100tominimisetuberweightloss
bullAllowcropstobestoredfreefromcondensationinchangeableweatherconditions
ControlledventilationControlledventilationallowscroprespirationheattoberemovedandthecroptobedriedandcooledFansarepositionedtocreateaflowofairthroughthecrop(positiveventilationbulkorbox)ortoformarollingmassofairthatwillflowoverthestackofboxesandthroughtheirpalletslots(spaceventilation)
Coolingcanbeachievedusingambientairandormechanicalcooling(refrigeration)Internalrecirculationofair(withoutcooling)canbeusedtoeliminatetemperaturevariationortodistributechemicalsforsproutsuppressionordiseasecontrol
AirflowshouldbeasuniformaspossiblethroughoutthestoretogiveevendryingandstablecroptemperaturesAwelldesignedstorewillhavebeenbalancedtoachieveuniformityofairflowatitstypicaloperatingconditionThismightincludefeaturessuchastaperedairductsorgraduatedlateraloutletstodeliversimilarquantitiesofairacrossthewholestore
Figure 21 A well sealed and insulated potato store
11S T O R E m a n a g E R S rsquo g U I D E
foundinpotatostoreswherecompositemetalpolyisocyanurate(PIR)sandwichpanelsareusedThesearecommonplacenowadaysfornewlybuiltstoresOthersystemsforupgradesofferatbestlittlemorethanavapourcheckThistendstolimitthechoiceofinsulationtoeithersprayorboardpolyurethaneoralternativelyexpandedextrudedpolystyreneboard
Specialistadviceshouldbesoughtforallaspectsofstoragebuildingdesign
equipmentwillalwaysincreasewaterlossfromthecropItisthereforejustasbeneficialtouseinsulationtolimitanyheatingressintothestoreasitistominimisetheeffectsofcoldweatherAlight-colouredreflectiveexternalsurfacewillreduceunwantedsolarradiationgains
NearlyallinsulationmaterialshavetheirperformancereducedsignificantlybyverysmallincreasesintheirmoisturecontentTheuseofvapourbarrierstoprotectinsulationisonlyeffectiveinthehighhumidityconditions
Storeassessment
bullUndertakeadetailedassessmentofyourstoreasdescribedinsection1
Balancedventilation
bullTheventilationsysteminastoreshouldbeinbalanceThismeansthatforoptimalperformancedesignfeaturesarerequiredndashegtaperedductsndashtooffsettheeffectsofpressuredropintheventilationsystemP8
doorsandlouvres
bullDoorsandlouvresaretheweakpointsoftheinsulationlsquoenvelopersquoMakesuretheycloseproperlyandstayclosedRegularpositiveactuationfromacontrollerisbeneficialforkeepingambientlouverswhicharesubjecttowindpressureclosed
Insulation
bullEnsurestoreinsulationisingoodconditionandeffective
bullWatchforsignsofcondensationwithinthestructurethatwilldegradetheinsulationvalueegdelaminatedinsulationboardswheremoisturehasgotinbehindthepanels
bullEnsureanynewbuildwithcompositeconstructionusesPIRpanelswhichareresistanttospreadofflameinthecoreintheeventoffire
ACTION POINTS
StorAGEBuILdInGS
Figure 22 Building envelope stabilises internal climate
12 S T O R E m a n a g E R S rsquo g U I D E
AllotherthingsbeingequalmoisturelossisafunctionofstorehumidityandairflowratePotatostoreswillusuallysettletoapproximately98relativehumidityandintheabsenceofahumidificationsystemthiswillbederivedbyevaporationofmoisturefromtubersInappropriatelyspecifiedrefrigerationunitscanexacerbatemoistureloss
dormancyFreshlyharvestedtubersusuallydonotsproutevenwhenconditionsareoptimalforsproutgrowthTheperiodoverwhichsproutgrowthisinhibitedbytuberphysiologyratherthanenvironmentalreasonsistermedthedormantperiodorsimplylsquodormancyrsquo
LargedifferencesindormancyoccurbetweenvarietiesWarmstoragetemperatureshaveadormancy-breakingeffectSelectionofvarietiesbydormancycharacteristicscanbeusefulforminimisingsprout-suppressantinputs
Dormancybreakistakenasthepointwhere50oftubershavesproutsof3mmormoreinlengthWarmdrysummerstendtoreducedormancy(inextremecasesleadingtosproutgrowthinthefieldbeforeharvest)whilecoolgrowingconditionswillgenerallyprolongitWaterlogginghasadormancy-breakingeffect
Woundhealing(curing)Wheretubershavebeensubjectedtowounding(egbyhandlingduringharvest)thetuberwillattempttohealthewoundndashaprocessinvolvingsuberisationandcell-divisionThespeedofthisprocesswhichisimportantforpreventingmoisturelossanddiseaseingressisaffectedbyanumberoffactorsTheseincludestoragetemperatureandhumiditywithwarmertemperaturesandhigherhumidityreducingthetimerequiredforwound-healing
Althougheffectivewound-healingisimportantconditionsthatareoptimalforcuringmayalsobesuitablefordiseasedevelopmentWherecropsareharvestedearlyundergoodconditionsorwherethestoragedurationislimitedsufficientcuringmayoccurduringtheperiodoverwhichcroptemperatureisreducedtotheholdingvalueP11
3 Cropphysiology
respirationPotatotubersarelivingorganismsandinstorecontinuetorespireandrespondtotheirenvironmentTheydosobyusingsugarsfromstarchinrespirationThisprocessconsumesoxygenandreleasescarbondioxideandsomeheatenergywhichimpactonstoragesystems
Respirationishighestatharvestandfallsrapidlytoabasallevelinthefirstweeksofstorage(Figure31)Respirationisgreaterinearly-liftedimmaturecropsthaninlate-liftedmaturecrops
Basalrespirationratedependspredominantlyonstoragetemperature(Figure32)Minimumrespirationrateisachievedataround5oCwiththerateincreasingaboveorbelowthistemperature
Handlingmechanicaldamageexposuretoethyleneandsproutingwillleadtoanincreaseinrespirationrate
EvaporationAlthoughsomemoistureislostintheprocessofrespirationmostislostbysimpleevaporationfromthetubersurfaceEffectivewound-healingandsproutcontrolisimportantinlimitingmoisturelossfromtubers
Figure 31 Respiration after lifting ndash early harvest
Figure 33 Moisture exchange between tuber skin and surrounding air in balance at ~98 relative humidity
Figure 32 Respiration in relation to storage temperature
1 2 3 4 5 6 7 8 9 10
Hea
t out
put (
Wto
nne)
35
0
5
10
15
20
25
30
Harvest date 9 September
Days after harvest
Harvest date 20 October
5 15 25
Rat
e of
resp
iratio
n (m
g C
O2k
ghr
)
12
0
2
4
6
8
10
Storage temperature (˚C)
13S T O R E m a n a g E R S rsquo g U I D E
ThisisaccomplishedsimplybyincreasingstoragetemperatureHoweverreconditioningleadstovariabilityinfrycolourandisthereforenotrecommendedasaroutinestoragepractice
PreconditioningmayalsobeusedtomaintainprocessingqualityHeretherearenodistinctcuringpull-downholdingperiodsandfrycolourorsugarcontentisusedtodeterminecropstoragetemperatureTemperaturereductiontoatargetholdingvalueonlyoccursprovidinggoodprocessingqualityismaintained
GreeningandglycoalkaloidsTubersexposedtolightwillturngreenwhichresultsfromthesynthesisofchlorophyllChlorophyllisitselfharmlessbutgreentubersaregenerallyrejectedbecausetheyhaveelevatedlevelsofglycoalkaloidsagroupofnaturaltoxicantspresentinpotatoes
TopreventgreeninginstorageexposuretolightshouldthereforebeminimisedalthoughtheneedtoseethecropclearlyandhealthandsafetyrequirementsP21willoverridethisduringloadingandsubsequentshortperiodswhenstoresareaccessedtobeinspectedorsampled
SugarsandconditioningPotatoescontainthreemainsugarsglucoseandfructose(monosaccharides)andsucrose(adisaccharide)AllthreesugarsaresweetandareimportantflavourcomponentsinwarepotatoesInpotatoesforprocessingthestoremanagerisprimarilyinterestedinthemonosaccharidesDuringprocessingthesereactwithothercomponentstoproducethebrowningwhichisassessedbymarketsasfrycolourAstoremanagersupplyingcropforprocessingmayalsobeinterestedinsucrosecontentAlthoughsucrosedoesnottakepartinbrowningreactionstrendsinsucroselevelsmaybeusedtohelpensurelowreducingsugarsandlightfrycolourduringstorage
VarietygrowthstageandstoragetemperatureareimportantindeterminingtubersugarcontentPotatoesexhibitlowtemperature-sweeteningwheresugarsaccumulatewithinthetuberastemperatureisreducedDuringstorageforprocessingtemperatureshouldthereforebemaintainedatthelowestlevelthatsafelymaintainsacceptablefrycolour
Forprocessingcropschangesinsugarcontent(andhencefrycolour)canbeachievedusingreconditioning
respiration
Thegreatertherespirationrateofthepotatoesthemorelikelyitisthatwarmairwillcondenseoncoolersurfacepotatoes
bullPositivelyventilatepotatoestoremoverespirationheattopreventsurfacecondensation
bullUsehighventilationratestopreventcondensationinheavilyrespiringearly-liftedorimmaturecropsP11
Evaporation
Moisturelossfrompotatoesduetoevaporationwilloccuriftherelativehumidity(RH)oftheairsurroundingthepotatoesislessthan98
bullKeepstorewell-sealedtominimiseweightloss
bullPreventuncontrolledexternalairingressasthisusuallyhasalowerRHthanthestorageenvironment
Sugars
Sugarsincreaseandfrycolourswilldarkenifpotatoesarestoredatcoldtemperatures
bullStorecropsforprocessingatc7-10degC
bullMonitorcold-storedpre-packpotatoesforeffectsofsugarincreaseontaste
bullIfunsurecheckstoragerequirementswithyourcustomer
ACTION POINTS
CroPPHYSIoLoGY
14 S T O R E m a n a g E R S rsquo g U I D E
Silverscurf Blackdot Skinspot dryrot Gangrene Softrot
moderateinfection
severeinfection
4 Controlofstoragediseases
DiseasecontrolisafundamentalcomponentofstoragemanagementMostdiseasesdonotoriginateinstoretheycomefromtwoprimarysourcestheseedorthesoilHowevermanyofthediseaseproblemsaffectingthepremiummarketscandeveloptosomedegreeinstoreandifnotcontrolledtheconsequencescanbecatastrophiceitherintermsofphysicalbreakdownofthecroporinlossofmarketvalueWhetherdiseasewilldevelopinstoreornot(Figure41)dependson
bullTheamountofinoculumusuallysporesorbacteriapresentonthetubersbullWhethermoisturenutrientsandtemperaturearesuitableforthediseasetogrowbullThenaturalresistanceofthetubertothediseaseorganism
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
15S T O R E m a n a g E R S rsquo g U I D E
Storemanagementallowsustoinfluencethisrelationshipparticularlyinrelationtothemicro-climatearoundthetubertocontroldiseasesduringstorage
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
Micro-climate Tuberresistance
Inoculum
Figure 41 Interaction between micro-climate and disease
notifiablediseases
SomediseasesarenotindigenousinBritainandtheirestablishmentwouldaffectthelong-termviabilityofthepotatoindustryIfsymptomsofeitherbrownrotorringrotaresuspectedthenimmediatecontactwithlocalDEFRAofficesorPlantHealthandSeedinspectorateisnecessaryVisitwwwdefragovukplanthphhtmemailplanthealthinfodefragsigovukortelephone01904455174toreportsuspectedcasesinEnglandandWalesInScotlandvisitwwwsasagovukplant_health
PreventativemeasuresexistGotowwwpotatoorguksafehaventolearnmoreaboutnationalschemesthatprotectseedandwarecrophealth
ringrotBrownrot
16 S T O R E m a n a g E R S rsquo g U I D E
Figure 52 Ensure dust and debris are removed from ducts
CrosscontaminationofsporesbetweenpotatostocksisinevitableFanventilationwithinthestoremayincreasethespeedofthismovementcomparedwithnaturalconvectionButtheairflowisabenefitasithelpskeepthecropfreefromcondensationpreventinganysporeswhichdosettlefromgerminating
MajordustmovementanddispersaloccurswhenforklifttrucksstirupdustonthefloorduringhandlingTheresultantdustcloudwillsettleontopofthecropwherethecondensationneededforgerminationismostlikelyIfgradingiscarriedoutwithinthestorethiswillalsocreateaconsiderabledustcloudwithsimilarconsequences
dustremovalSweepingwithabrushmovestheheavierdustparticlesalongthefloorwhilecreatingacloudoflighterparticleswhichincludesthemajorityofsporesVacuumingloosensandremovesallfractionsofdustandiffittedwithafinefilterwillremovemostharmfulsporesfromthestoreVacuumingisthereforemuchpreferredtosweeping
disinfectionRemovingdustandsquashedtuberswillremovethemajorityofinoculumpresentSomedustandsporeswillremainonthefloorwallsandraftersaswellasthefloorandsidesofpotatoboxesthemajorityofwhichcanberemovedbypowerwashingIftotalremovalofviablesporesisrequiredegforhighhealthcropsadisinfectantcanbeusedThisisparticularlyrelevantinstoreswheredamagerelateddiseasessuchasdryrothaveoccurred
5 Storehygiene
AcleanstorefreefromdiscardedtubersdustanddebrishasanumberofadvantagesItwillminimisecropinfectionimproveairflowcontributetoworkerhealthandcomfortandislikelytoimpressclientsandcustomers
SomesoilisinevitablybroughtintostorewiththeharvestedcropOncedrythisbecomesapotentialsourceofdustwhenthecropismovedIfthecropisfreeofdiseasewhenharvestedanditremainssooverthestorageperiodthenthedustwillbemainlymineralinnatureHoweverifthecropisdiseasedorbecomessoduringstoragethedustmaycontainlargequantitiesofsporeswhichwillbeasourceofinoculuminthepresentorfutureyears
dustdispersalConvectioncurrentscausedbyrespirationheatfromthecropwillcirculatedustandsporesthroughoutthestore
Figure 51 Vacuuming of potato store
17S T O R E m a n a g E R S rsquo g U I D E
StorEHYGIEnE
Post-storagecleaning
bullStore-cleaningshouldbeundertakenannuallyInboxstoresthisisbestcarriedoutimmediatelyafterthelastcrophasbeenremovedsocleanedboxescanbereturnedtostore
bullInayearfollowingcropinfectionbysilverscurforskinspotextrarigorouscleaningshouldbecarriedout
bullVacuumdirtanddebrisfromfloorsledgesbeamsandotherhorizontalsurfaces
bullWhereinsulationisdamagedorisroughandcollectsdustrepairandvacuum
bullOnlypowerhoseifinsulationismoisture-proof
Cleaningboxes
bullEnsurethatbox-tippersongradinglinesaredesignedtodischargethetotalboxcontentstogetridofmajorcontamination
bullUsepowerhosetocleanboxes
bullWherecleaningboxesisroutineconsidersettingupaconveyor-basedautomaticwashingsystem
bullPower-washboxesforhighhealthcrops
bullWherepossiblereturncleanedboxestostoreorkeepundercoverasthiscanextendboxlifeby70
Whentousedisinfectants
Forhighhealthseedcropsdisinfectantsmaybebeneficialespeciallyafteracontaminatedcropinthepreviousyear
bullUsedisinfectantmistfogorsprayaftervacuumingstore
bullSpraydisinfectboxeswhichhelddiseasedcropout-gradesorlsquobrockrsquo
bullFollowinggradingofdiseasedpotatoespower-washgradinglinethenspraywithdisinfectantwheregradinghighhealthcrops
bullAlwaysuseapprovedproductsandseekspecialistadvice
notesomedisinfectantsmaydamagestoreinsulationandelectricalfittingsndashconsulttheproductlabelbeforeuse
dailycleaning
bullVacuumthefloorparticularlyforkliftroutesandundergradersatleastonceaday
Gradinginstore
GradinginstoreislikelytoincreasetheamountofcontaminateddustinthestoreandthelikelihoodofambientairenteringthroughopendoorsDustprovidesdiseaseinoculumwhileambientairmaycausecondensationparticularlyonthetopsurfaceofboxesorpile
bullIdeallygradeinseparatebuildingwithaplasticstripdoorbetweenthestoreandgradingarea
bullIfgradinginstoreisunavoidableenclosepickersinwarmedcabinandfitadustcontrolsystemtotheline
bullFitdewpointtemperaturemonitortowarnofcondensationrisks
ACTION POINTS
LeavingboxesoutsidewillallowlighttokillviablesporesBoxesshouldnotbestackedmorethanfourboxeshighforsafetyandifstackedinpairsasmallgapbetweenrowswillallownatural(ultraviolet)lighttoreachonesideofeveryboxHoweveroutsidestackingcanreduceboxlifebyupto40
CleaningandenergyefficiencyMaintainingfansventilationandrefrigerationequipmentinacleanconditionwillhelpprolongtheirworkinglifeand
improvetheirworkingefficiencyEnsurethattemperatureandhumidityprobesarekeptcleanandinspectlouvresevaporatorsandcondensersIfnecessarycleanbyvacuumingorpowerwashingIfwashingtakecarearoundelectricalandmovingsystemsandensurethatanyresultingiceisremovedbydefrosting
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
5S T O R E m a n a g E R S rsquo g U I D E
12 StruCturALCondEnSAtIon 30 Whystructuralcondensationoccurspreventativemeasuresroofspaceheating
13 rEFrIGErAtIon 32 Environmentalcontrolcoolingratesmaintenance
14 HuMIdItY 34 Humidityandmoisturelosshumidification
15 EnErGYMAnAGEMEnt 36 Monitoringexamplecostsoptimisinguse
16 StorEAtMoSPHErE 38 Oxygencarbondioxideothervolatiles
17 StorAGEForMArKEtS 40 CostscropmonitoringgettingthebestfromQCsampling
18 SProutSuPPrESSIon 44 RequirementforsproutcontrolactiveingredientsoptimisinguseofCIPC
19 WArMInG 46 Physicsofwarmingsystemstousedryingofskinsandlsquofingernailrsquodamage
20 StorEMonItorInGAndQuALItYASSurAnCE 48 Recordkeepingandprotocolsstoremonitoringanddatalogging
21 HEALtHAndSAFEtY 50 Workingatheightrisksinstoressafetyclothing
Appendices
1Bibliography 52
2Glossaryofterms 53
3Metricequivalents 54
4dew-pointtable 55
6 S T O R E m a n a g E R S rsquo g U I D E
1 Storeself-assessment
ForeachstorefeatureinthetableconsiderthefactorslistedandringthedescriptiononeachlinewhichbestsummarisesyourownstoreUsetheassessmenttoidentifythoseareaswhereimprovementscanbemade(anyscoring1asaminimum)andconsulttheappropriatesectionforfurtherinformationSomeproblemsmaybeeasytosolveandwillquicklyproducesignificantbenefitsothersmayneedlonger-termplanningtorectify
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
HYGIEnE
Cleaningfrequency
Mainmethodusedwhere
VErMInControL
HIGHrISKoFContAMInAtIonNocleaning
Sweeping
Nospecificmeasures
CleanedannuallyVacuumampdebrisremoval
Floorandwalls
Controlmeasuresinplacewithinstore
Vacuum+wash
+washboxesampmainsurfaces
VErYLoWdISEASErISKStorecleaneddaily+disinfectantapplied
+fogappliedtoentirestore
Accreditedprofessionalpestcontrolforfarm
Storehygiene
StruCturE
Storefabric
door(s)
Exposure
LEAKYPronEtoCondEnSAtIonLotoflightenters
2ormoregapsallround
Noshelter
Somelightenters
Door(s)sealedwithbrushesorrubber
Shelteredfromprevailingwind
Oddpinpricksoflight
Oneexternaldooronlysealedallround
Shelteredallround
SEALEdControLLABLECompletelydark
Noexternaldoorsloadviagradingarea
Singledoorexitstogradingarea
Storagebuildingsampcondensationonthecrop
InSuLAtIon
roof
Wall
noInSuLAtIon
Singleskinroof
Brickblockstonewalls
Doubleskin+glassfibreroof
Lightweightcavitywalls
lt75mmEEPsprayfoam
Compositepanel+gt50mmfoamEEP
HIGHLEVELInSuLAtIon75mm+foamEEPinsulation
Ascolumn3butgt75mm
Storagebuildings
7S T O R E m a n a g E R S rsquo g U I D E
bullringthedescriptionswhichmostcloselydescribeyourstorebullConsiderthefactorsandrisksthisself-assessmentidentifiesbulldecideonanyactionneededbullrefertotheappropriatesectionoftheguideorseekfurtherspecialistadvice
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
VEntILAtIon
Bulkstoresystem
Boxstoresystem
Boxstoreairdistribution
recirculation
HIGHrISKoFContAMInAtIonNofanopendooronly
Nofanopendooronly
Aroundboxesnosingleldquoairrollrdquoestablished
None
Fanslt002m3st
Fanslt002m3st
Spaceventilationformsrollofairpartviaboxapertures
Someairmovementbutnoairroll
Spaceventilationampfansge002m3st
Ascolumn2+rooffansorpositiveventilationwithtraditionalboxes
Intermittentlt002m3stLowratepartstore
PoSItIVEampFAStdrYInGFansge002m3st
Positiveventilationampfansge004m3st
Positiveventilationusingpurposedesignedboxes
Intermittentge002m3stLowratecontinuous
Ventilation
FAnSYStEMS
Fantype
Fanefficiency
Ventilationcontrol
Mixing
Inletairprotection
unControLLEdrISKtoCroP
Centrifugalfan
Oldagedfanwithbigstartingload
Onoffswitching
Manual
Nofrostthermostat
Axial(propellerstyle)
Modernfan(s)withpower-factorcorrection
Automaticswitchingofsinglemultiplefans
Autonoairmixing
Thermostattocutfanoffineventoffrost
Automatedaxialfans
High-efficiencyfansforlowrunningcost
Manualspeedcontrolofautomaticsinglemultiplefans
Auto+airmixing
Inlettemperaturecontrol
FuLLControLoFCooLInG
AxialfansforpositiveventilationSoftstarthigh-efficiencylownoisefans
Automatedvariablespeedcontroloffans
Auto+airmixingampdew-pointcontrol
Inlettemperature+condensationcontrol
Ventilation
8 S T O R E m a n a g E R S rsquo g U I D E
1 Storeself-assessment
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
BoXStACKInG
Spaceventilatedstores
Cross-stackedboxes(ieat90degtomainblock)
Boxheight
rEStrICtEdAIrFLoWrISKoFCondEnSAtIonBoxesstackedrandomly
Boxesstackedacrosspalletslotsofmainblock
Inconsistentstackingheightthroughoutstore
Gapsacrossstore(riskofshortcircuiting)
Boxescross-stackedawayfrommainblocktoallowairtoenterpalletapertures
Rowsateaves1boxlowercapacityeconomicsdictate
Gapsgt150mmbetweenrows
Slattedboxeslessrestrictivetoairflowwhencross-stackedifonly2wide
Allboxesatsameheight
oPtIMALAIrFLoWLoWrISKoFCondEnSAtIonGapslt150mmandsupplementaryfanstotargetlsquodeadspotsrsquo
Boxesstackedat90degtoairflowwith50mmgapsbetweenalternateboxeswithinrows
Allboxesatsameheightroofspaceventilatedheated
Loadingthestore
rEFrIGErAtIon
Fridgesystemsizeampperformance
Spaceventilationcoolingrate
Positiveventilationcoolingrate
dEHYdrAtIonrISK
Smallfridgecoilwithair-onair-offtempdifferencegt35degC
Longrunningtimesnoeffectivecooling
Asabove
Coolsatlt025degCday
Coolsatlt05degCday
Coolsatgt05degCday
Coolsatgt1degCday(ManagecondensationriskP11)
FrIdGESIZEoPtIMAL
Air-onair-offtemperaturedifference~25degC
Coolsat~05degCday
Coolsat~1degCday
Refrigeration
9S T O R E m a n a g E R S rsquo g U I D E
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
MonItorInGAndtrACEABILtY
temperaturesensors
Bulkstacksensorplacement
Condensationcontrol
Stockcontrol
Storerecording
LACKoFControL
Nosensorsinstore
Asabove
Asabove
Chemicalrecordsonlylegalminimum
Asabove
Inaironlycropconditionunknown
Topsurfaceonly-pronetoinfluencebyairabove
Controloftemperaturedifferentials
Chemicaluseplusstocklocationinstorerecorded
Occasionalmanualrecordingofstoretemperatures
1or2sensorsincropnomeasureoftemperaturevariation
Topandbaseofstacktomeasurepiletemperaturegradient
Relativehumiditymeasurementfordew-pointcontrol
Chemicalusestockdetailslabelledoneachbox
Regularmanualrecordingofstoretemperaturesandfanrunningtimes
FuLLCAPABILItY
1sensorper100tonnes
Ascolumn3butalso300mmdowntoanticipatecondensation
Skinresistancesensingtomeasureanywetting
Boxrecordsincludelocation-feedbackonstorageproblems
Automaticloggingofstoretemperaturesandfanrunningtimes
LoadingthestoreampStoremonitoringandqualityassurance
QCSAMPLInG Singlepointsampling Multi-pointsampling
ononelevelMulti-pointsamplingonmorethanonelevel
Comprehensivesamplingthroughoutthestore
Storageformarkets
SEEdGrAdInG
CondEnSAtIonrISK
Instore Nextdoorbutnoairlock
Nextdoorwithstripcurtain
StorEISoLAtEd
Nextdoorwithhighspeeddoor
Condensationonthecrop
10 S T O R E m a n a g E R S rsquo g U I D E
Fabricordoorleakagetowind-inducedventilationreducesthebenefitsofthestoreasitislikelytoleadtolossofenvironmentalcontrolcropweightlossandpossiblecondensationonthecropVentilationorrefrigerationrun-timewillincreasetocoolthecropwarmedbytheleakingair
ContainmentThecapitalcostofabulkstorewithload-bearinginsulatedretainingwallsishigherthanforaboxstoreButwhenthecapitalcostofboxesisaddedbulkstorageischeaperoverallBoxstoreseaseseparationfordifferentstocksandprovidemoreflexibilityforcropmovementandmarketingDeepbulkpilescanleadtopressurebruisingproblemsifthecropisstoredover40mhighorifexcessivelyventilatedbynon-humidifiedairBoxstorageisnormallyfreefrompressurebruisinganddependingontheirqualityboxescanbestackedupto8high
InsulationThequalityoftheinsulationwilldeterminetoalargeextenthowwellapotatostoreperformsInsulationisakeyfactorforapotatostoremuchmoresothanitisforgeneralpurposebuildings
MaintainingtemperaturesabovefreezingpointisseldomaproblemgiventhequantityofheatproducedinalargestoreHoweveranyheatthatleaksintoastorehastoberemovedbyexpendingenergyeitherintheformofventilationorrefrigerationInadditiontotheimplicationsoncosttheavoidableoperationofenvironmentalcontrol
2 Storagebuildings
Awellsealedandinsulatedpotatostore(Figure21)will
bullAllowthecroptobekeptatastabletemperaturelargelyunaffectedbydiurnalvariationandambientconditions
bullHelpmaintainarelativehumidityof90-100tominimisetuberweightloss
bullAllowcropstobestoredfreefromcondensationinchangeableweatherconditions
ControlledventilationControlledventilationallowscroprespirationheattoberemovedandthecroptobedriedandcooledFansarepositionedtocreateaflowofairthroughthecrop(positiveventilationbulkorbox)ortoformarollingmassofairthatwillflowoverthestackofboxesandthroughtheirpalletslots(spaceventilation)
Coolingcanbeachievedusingambientairandormechanicalcooling(refrigeration)Internalrecirculationofair(withoutcooling)canbeusedtoeliminatetemperaturevariationortodistributechemicalsforsproutsuppressionordiseasecontrol
AirflowshouldbeasuniformaspossiblethroughoutthestoretogiveevendryingandstablecroptemperaturesAwelldesignedstorewillhavebeenbalancedtoachieveuniformityofairflowatitstypicaloperatingconditionThismightincludefeaturessuchastaperedairductsorgraduatedlateraloutletstodeliversimilarquantitiesofairacrossthewholestore
Figure 21 A well sealed and insulated potato store
11S T O R E m a n a g E R S rsquo g U I D E
foundinpotatostoreswherecompositemetalpolyisocyanurate(PIR)sandwichpanelsareusedThesearecommonplacenowadaysfornewlybuiltstoresOthersystemsforupgradesofferatbestlittlemorethanavapourcheckThistendstolimitthechoiceofinsulationtoeithersprayorboardpolyurethaneoralternativelyexpandedextrudedpolystyreneboard
Specialistadviceshouldbesoughtforallaspectsofstoragebuildingdesign
equipmentwillalwaysincreasewaterlossfromthecropItisthereforejustasbeneficialtouseinsulationtolimitanyheatingressintothestoreasitistominimisetheeffectsofcoldweatherAlight-colouredreflectiveexternalsurfacewillreduceunwantedsolarradiationgains
NearlyallinsulationmaterialshavetheirperformancereducedsignificantlybyverysmallincreasesintheirmoisturecontentTheuseofvapourbarrierstoprotectinsulationisonlyeffectiveinthehighhumidityconditions
Storeassessment
bullUndertakeadetailedassessmentofyourstoreasdescribedinsection1
Balancedventilation
bullTheventilationsysteminastoreshouldbeinbalanceThismeansthatforoptimalperformancedesignfeaturesarerequiredndashegtaperedductsndashtooffsettheeffectsofpressuredropintheventilationsystemP8
doorsandlouvres
bullDoorsandlouvresaretheweakpointsoftheinsulationlsquoenvelopersquoMakesuretheycloseproperlyandstayclosedRegularpositiveactuationfromacontrollerisbeneficialforkeepingambientlouverswhicharesubjecttowindpressureclosed
Insulation
bullEnsurestoreinsulationisingoodconditionandeffective
bullWatchforsignsofcondensationwithinthestructurethatwilldegradetheinsulationvalueegdelaminatedinsulationboardswheremoisturehasgotinbehindthepanels
bullEnsureanynewbuildwithcompositeconstructionusesPIRpanelswhichareresistanttospreadofflameinthecoreintheeventoffire
ACTION POINTS
StorAGEBuILdInGS
Figure 22 Building envelope stabilises internal climate
12 S T O R E m a n a g E R S rsquo g U I D E
AllotherthingsbeingequalmoisturelossisafunctionofstorehumidityandairflowratePotatostoreswillusuallysettletoapproximately98relativehumidityandintheabsenceofahumidificationsystemthiswillbederivedbyevaporationofmoisturefromtubersInappropriatelyspecifiedrefrigerationunitscanexacerbatemoistureloss
dormancyFreshlyharvestedtubersusuallydonotsproutevenwhenconditionsareoptimalforsproutgrowthTheperiodoverwhichsproutgrowthisinhibitedbytuberphysiologyratherthanenvironmentalreasonsistermedthedormantperiodorsimplylsquodormancyrsquo
LargedifferencesindormancyoccurbetweenvarietiesWarmstoragetemperatureshaveadormancy-breakingeffectSelectionofvarietiesbydormancycharacteristicscanbeusefulforminimisingsprout-suppressantinputs
Dormancybreakistakenasthepointwhere50oftubershavesproutsof3mmormoreinlengthWarmdrysummerstendtoreducedormancy(inextremecasesleadingtosproutgrowthinthefieldbeforeharvest)whilecoolgrowingconditionswillgenerallyprolongitWaterlogginghasadormancy-breakingeffect
Woundhealing(curing)Wheretubershavebeensubjectedtowounding(egbyhandlingduringharvest)thetuberwillattempttohealthewoundndashaprocessinvolvingsuberisationandcell-divisionThespeedofthisprocesswhichisimportantforpreventingmoisturelossanddiseaseingressisaffectedbyanumberoffactorsTheseincludestoragetemperatureandhumiditywithwarmertemperaturesandhigherhumidityreducingthetimerequiredforwound-healing
Althougheffectivewound-healingisimportantconditionsthatareoptimalforcuringmayalsobesuitablefordiseasedevelopmentWherecropsareharvestedearlyundergoodconditionsorwherethestoragedurationislimitedsufficientcuringmayoccurduringtheperiodoverwhichcroptemperatureisreducedtotheholdingvalueP11
3 Cropphysiology
respirationPotatotubersarelivingorganismsandinstorecontinuetorespireandrespondtotheirenvironmentTheydosobyusingsugarsfromstarchinrespirationThisprocessconsumesoxygenandreleasescarbondioxideandsomeheatenergywhichimpactonstoragesystems
Respirationishighestatharvestandfallsrapidlytoabasallevelinthefirstweeksofstorage(Figure31)Respirationisgreaterinearly-liftedimmaturecropsthaninlate-liftedmaturecrops
Basalrespirationratedependspredominantlyonstoragetemperature(Figure32)Minimumrespirationrateisachievedataround5oCwiththerateincreasingaboveorbelowthistemperature
Handlingmechanicaldamageexposuretoethyleneandsproutingwillleadtoanincreaseinrespirationrate
EvaporationAlthoughsomemoistureislostintheprocessofrespirationmostislostbysimpleevaporationfromthetubersurfaceEffectivewound-healingandsproutcontrolisimportantinlimitingmoisturelossfromtubers
Figure 31 Respiration after lifting ndash early harvest
Figure 33 Moisture exchange between tuber skin and surrounding air in balance at ~98 relative humidity
Figure 32 Respiration in relation to storage temperature
1 2 3 4 5 6 7 8 9 10
Hea
t out
put (
Wto
nne)
35
0
5
10
15
20
25
30
Harvest date 9 September
Days after harvest
Harvest date 20 October
5 15 25
Rat
e of
resp
iratio
n (m
g C
O2k
ghr
)
12
0
2
4
6
8
10
Storage temperature (˚C)
13S T O R E m a n a g E R S rsquo g U I D E
ThisisaccomplishedsimplybyincreasingstoragetemperatureHoweverreconditioningleadstovariabilityinfrycolourandisthereforenotrecommendedasaroutinestoragepractice
PreconditioningmayalsobeusedtomaintainprocessingqualityHeretherearenodistinctcuringpull-downholdingperiodsandfrycolourorsugarcontentisusedtodeterminecropstoragetemperatureTemperaturereductiontoatargetholdingvalueonlyoccursprovidinggoodprocessingqualityismaintained
GreeningandglycoalkaloidsTubersexposedtolightwillturngreenwhichresultsfromthesynthesisofchlorophyllChlorophyllisitselfharmlessbutgreentubersaregenerallyrejectedbecausetheyhaveelevatedlevelsofglycoalkaloidsagroupofnaturaltoxicantspresentinpotatoes
TopreventgreeninginstorageexposuretolightshouldthereforebeminimisedalthoughtheneedtoseethecropclearlyandhealthandsafetyrequirementsP21willoverridethisduringloadingandsubsequentshortperiodswhenstoresareaccessedtobeinspectedorsampled
SugarsandconditioningPotatoescontainthreemainsugarsglucoseandfructose(monosaccharides)andsucrose(adisaccharide)AllthreesugarsaresweetandareimportantflavourcomponentsinwarepotatoesInpotatoesforprocessingthestoremanagerisprimarilyinterestedinthemonosaccharidesDuringprocessingthesereactwithothercomponentstoproducethebrowningwhichisassessedbymarketsasfrycolourAstoremanagersupplyingcropforprocessingmayalsobeinterestedinsucrosecontentAlthoughsucrosedoesnottakepartinbrowningreactionstrendsinsucroselevelsmaybeusedtohelpensurelowreducingsugarsandlightfrycolourduringstorage
VarietygrowthstageandstoragetemperatureareimportantindeterminingtubersugarcontentPotatoesexhibitlowtemperature-sweeteningwheresugarsaccumulatewithinthetuberastemperatureisreducedDuringstorageforprocessingtemperatureshouldthereforebemaintainedatthelowestlevelthatsafelymaintainsacceptablefrycolour
Forprocessingcropschangesinsugarcontent(andhencefrycolour)canbeachievedusingreconditioning
respiration
Thegreatertherespirationrateofthepotatoesthemorelikelyitisthatwarmairwillcondenseoncoolersurfacepotatoes
bullPositivelyventilatepotatoestoremoverespirationheattopreventsurfacecondensation
bullUsehighventilationratestopreventcondensationinheavilyrespiringearly-liftedorimmaturecropsP11
Evaporation
Moisturelossfrompotatoesduetoevaporationwilloccuriftherelativehumidity(RH)oftheairsurroundingthepotatoesislessthan98
bullKeepstorewell-sealedtominimiseweightloss
bullPreventuncontrolledexternalairingressasthisusuallyhasalowerRHthanthestorageenvironment
Sugars
Sugarsincreaseandfrycolourswilldarkenifpotatoesarestoredatcoldtemperatures
bullStorecropsforprocessingatc7-10degC
bullMonitorcold-storedpre-packpotatoesforeffectsofsugarincreaseontaste
bullIfunsurecheckstoragerequirementswithyourcustomer
ACTION POINTS
CroPPHYSIoLoGY
14 S T O R E m a n a g E R S rsquo g U I D E
Silverscurf Blackdot Skinspot dryrot Gangrene Softrot
moderateinfection
severeinfection
4 Controlofstoragediseases
DiseasecontrolisafundamentalcomponentofstoragemanagementMostdiseasesdonotoriginateinstoretheycomefromtwoprimarysourcestheseedorthesoilHowevermanyofthediseaseproblemsaffectingthepremiummarketscandeveloptosomedegreeinstoreandifnotcontrolledtheconsequencescanbecatastrophiceitherintermsofphysicalbreakdownofthecroporinlossofmarketvalueWhetherdiseasewilldevelopinstoreornot(Figure41)dependson
bullTheamountofinoculumusuallysporesorbacteriapresentonthetubersbullWhethermoisturenutrientsandtemperaturearesuitableforthediseasetogrowbullThenaturalresistanceofthetubertothediseaseorganism
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
15S T O R E m a n a g E R S rsquo g U I D E
Storemanagementallowsustoinfluencethisrelationshipparticularlyinrelationtothemicro-climatearoundthetubertocontroldiseasesduringstorage
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
Micro-climate Tuberresistance
Inoculum
Figure 41 Interaction between micro-climate and disease
notifiablediseases
SomediseasesarenotindigenousinBritainandtheirestablishmentwouldaffectthelong-termviabilityofthepotatoindustryIfsymptomsofeitherbrownrotorringrotaresuspectedthenimmediatecontactwithlocalDEFRAofficesorPlantHealthandSeedinspectorateisnecessaryVisitwwwdefragovukplanthphhtmemailplanthealthinfodefragsigovukortelephone01904455174toreportsuspectedcasesinEnglandandWalesInScotlandvisitwwwsasagovukplant_health
PreventativemeasuresexistGotowwwpotatoorguksafehaventolearnmoreaboutnationalschemesthatprotectseedandwarecrophealth
ringrotBrownrot
16 S T O R E m a n a g E R S rsquo g U I D E
Figure 52 Ensure dust and debris are removed from ducts
CrosscontaminationofsporesbetweenpotatostocksisinevitableFanventilationwithinthestoremayincreasethespeedofthismovementcomparedwithnaturalconvectionButtheairflowisabenefitasithelpskeepthecropfreefromcondensationpreventinganysporeswhichdosettlefromgerminating
MajordustmovementanddispersaloccurswhenforklifttrucksstirupdustonthefloorduringhandlingTheresultantdustcloudwillsettleontopofthecropwherethecondensationneededforgerminationismostlikelyIfgradingiscarriedoutwithinthestorethiswillalsocreateaconsiderabledustcloudwithsimilarconsequences
dustremovalSweepingwithabrushmovestheheavierdustparticlesalongthefloorwhilecreatingacloudoflighterparticleswhichincludesthemajorityofsporesVacuumingloosensandremovesallfractionsofdustandiffittedwithafinefilterwillremovemostharmfulsporesfromthestoreVacuumingisthereforemuchpreferredtosweeping
disinfectionRemovingdustandsquashedtuberswillremovethemajorityofinoculumpresentSomedustandsporeswillremainonthefloorwallsandraftersaswellasthefloorandsidesofpotatoboxesthemajorityofwhichcanberemovedbypowerwashingIftotalremovalofviablesporesisrequiredegforhighhealthcropsadisinfectantcanbeusedThisisparticularlyrelevantinstoreswheredamagerelateddiseasessuchasdryrothaveoccurred
5 Storehygiene
AcleanstorefreefromdiscardedtubersdustanddebrishasanumberofadvantagesItwillminimisecropinfectionimproveairflowcontributetoworkerhealthandcomfortandislikelytoimpressclientsandcustomers
SomesoilisinevitablybroughtintostorewiththeharvestedcropOncedrythisbecomesapotentialsourceofdustwhenthecropismovedIfthecropisfreeofdiseasewhenharvestedanditremainssooverthestorageperiodthenthedustwillbemainlymineralinnatureHoweverifthecropisdiseasedorbecomessoduringstoragethedustmaycontainlargequantitiesofsporeswhichwillbeasourceofinoculuminthepresentorfutureyears
dustdispersalConvectioncurrentscausedbyrespirationheatfromthecropwillcirculatedustandsporesthroughoutthestore
Figure 51 Vacuuming of potato store
17S T O R E m a n a g E R S rsquo g U I D E
StorEHYGIEnE
Post-storagecleaning
bullStore-cleaningshouldbeundertakenannuallyInboxstoresthisisbestcarriedoutimmediatelyafterthelastcrophasbeenremovedsocleanedboxescanbereturnedtostore
bullInayearfollowingcropinfectionbysilverscurforskinspotextrarigorouscleaningshouldbecarriedout
bullVacuumdirtanddebrisfromfloorsledgesbeamsandotherhorizontalsurfaces
bullWhereinsulationisdamagedorisroughandcollectsdustrepairandvacuum
bullOnlypowerhoseifinsulationismoisture-proof
Cleaningboxes
bullEnsurethatbox-tippersongradinglinesaredesignedtodischargethetotalboxcontentstogetridofmajorcontamination
bullUsepowerhosetocleanboxes
bullWherecleaningboxesisroutineconsidersettingupaconveyor-basedautomaticwashingsystem
bullPower-washboxesforhighhealthcrops
bullWherepossiblereturncleanedboxestostoreorkeepundercoverasthiscanextendboxlifeby70
Whentousedisinfectants
Forhighhealthseedcropsdisinfectantsmaybebeneficialespeciallyafteracontaminatedcropinthepreviousyear
bullUsedisinfectantmistfogorsprayaftervacuumingstore
bullSpraydisinfectboxeswhichhelddiseasedcropout-gradesorlsquobrockrsquo
bullFollowinggradingofdiseasedpotatoespower-washgradinglinethenspraywithdisinfectantwheregradinghighhealthcrops
bullAlwaysuseapprovedproductsandseekspecialistadvice
notesomedisinfectantsmaydamagestoreinsulationandelectricalfittingsndashconsulttheproductlabelbeforeuse
dailycleaning
bullVacuumthefloorparticularlyforkliftroutesandundergradersatleastonceaday
Gradinginstore
GradinginstoreislikelytoincreasetheamountofcontaminateddustinthestoreandthelikelihoodofambientairenteringthroughopendoorsDustprovidesdiseaseinoculumwhileambientairmaycausecondensationparticularlyonthetopsurfaceofboxesorpile
bullIdeallygradeinseparatebuildingwithaplasticstripdoorbetweenthestoreandgradingarea
bullIfgradinginstoreisunavoidableenclosepickersinwarmedcabinandfitadustcontrolsystemtotheline
bullFitdewpointtemperaturemonitortowarnofcondensationrisks
ACTION POINTS
LeavingboxesoutsidewillallowlighttokillviablesporesBoxesshouldnotbestackedmorethanfourboxeshighforsafetyandifstackedinpairsasmallgapbetweenrowswillallownatural(ultraviolet)lighttoreachonesideofeveryboxHoweveroutsidestackingcanreduceboxlifebyupto40
CleaningandenergyefficiencyMaintainingfansventilationandrefrigerationequipmentinacleanconditionwillhelpprolongtheirworkinglifeand
improvetheirworkingefficiencyEnsurethattemperatureandhumidityprobesarekeptcleanandinspectlouvresevaporatorsandcondensersIfnecessarycleanbyvacuumingorpowerwashingIfwashingtakecarearoundelectricalandmovingsystemsandensurethatanyresultingiceisremovedbydefrosting
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
6 S T O R E m a n a g E R S rsquo g U I D E
1 Storeself-assessment
ForeachstorefeatureinthetableconsiderthefactorslistedandringthedescriptiononeachlinewhichbestsummarisesyourownstoreUsetheassessmenttoidentifythoseareaswhereimprovementscanbemade(anyscoring1asaminimum)andconsulttheappropriatesectionforfurtherinformationSomeproblemsmaybeeasytosolveandwillquicklyproducesignificantbenefitsothersmayneedlonger-termplanningtorectify
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
HYGIEnE
Cleaningfrequency
Mainmethodusedwhere
VErMInControL
HIGHrISKoFContAMInAtIonNocleaning
Sweeping
Nospecificmeasures
CleanedannuallyVacuumampdebrisremoval
Floorandwalls
Controlmeasuresinplacewithinstore
Vacuum+wash
+washboxesampmainsurfaces
VErYLoWdISEASErISKStorecleaneddaily+disinfectantapplied
+fogappliedtoentirestore
Accreditedprofessionalpestcontrolforfarm
Storehygiene
StruCturE
Storefabric
door(s)
Exposure
LEAKYPronEtoCondEnSAtIonLotoflightenters
2ormoregapsallround
Noshelter
Somelightenters
Door(s)sealedwithbrushesorrubber
Shelteredfromprevailingwind
Oddpinpricksoflight
Oneexternaldooronlysealedallround
Shelteredallround
SEALEdControLLABLECompletelydark
Noexternaldoorsloadviagradingarea
Singledoorexitstogradingarea
Storagebuildingsampcondensationonthecrop
InSuLAtIon
roof
Wall
noInSuLAtIon
Singleskinroof
Brickblockstonewalls
Doubleskin+glassfibreroof
Lightweightcavitywalls
lt75mmEEPsprayfoam
Compositepanel+gt50mmfoamEEP
HIGHLEVELInSuLAtIon75mm+foamEEPinsulation
Ascolumn3butgt75mm
Storagebuildings
7S T O R E m a n a g E R S rsquo g U I D E
bullringthedescriptionswhichmostcloselydescribeyourstorebullConsiderthefactorsandrisksthisself-assessmentidentifiesbulldecideonanyactionneededbullrefertotheappropriatesectionoftheguideorseekfurtherspecialistadvice
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
VEntILAtIon
Bulkstoresystem
Boxstoresystem
Boxstoreairdistribution
recirculation
HIGHrISKoFContAMInAtIonNofanopendooronly
Nofanopendooronly
Aroundboxesnosingleldquoairrollrdquoestablished
None
Fanslt002m3st
Fanslt002m3st
Spaceventilationformsrollofairpartviaboxapertures
Someairmovementbutnoairroll
Spaceventilationampfansge002m3st
Ascolumn2+rooffansorpositiveventilationwithtraditionalboxes
Intermittentlt002m3stLowratepartstore
PoSItIVEampFAStdrYInGFansge002m3st
Positiveventilationampfansge004m3st
Positiveventilationusingpurposedesignedboxes
Intermittentge002m3stLowratecontinuous
Ventilation
FAnSYStEMS
Fantype
Fanefficiency
Ventilationcontrol
Mixing
Inletairprotection
unControLLEdrISKtoCroP
Centrifugalfan
Oldagedfanwithbigstartingload
Onoffswitching
Manual
Nofrostthermostat
Axial(propellerstyle)
Modernfan(s)withpower-factorcorrection
Automaticswitchingofsinglemultiplefans
Autonoairmixing
Thermostattocutfanoffineventoffrost
Automatedaxialfans
High-efficiencyfansforlowrunningcost
Manualspeedcontrolofautomaticsinglemultiplefans
Auto+airmixing
Inlettemperaturecontrol
FuLLControLoFCooLInG
AxialfansforpositiveventilationSoftstarthigh-efficiencylownoisefans
Automatedvariablespeedcontroloffans
Auto+airmixingampdew-pointcontrol
Inlettemperature+condensationcontrol
Ventilation
8 S T O R E m a n a g E R S rsquo g U I D E
1 Storeself-assessment
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
BoXStACKInG
Spaceventilatedstores
Cross-stackedboxes(ieat90degtomainblock)
Boxheight
rEStrICtEdAIrFLoWrISKoFCondEnSAtIonBoxesstackedrandomly
Boxesstackedacrosspalletslotsofmainblock
Inconsistentstackingheightthroughoutstore
Gapsacrossstore(riskofshortcircuiting)
Boxescross-stackedawayfrommainblocktoallowairtoenterpalletapertures
Rowsateaves1boxlowercapacityeconomicsdictate
Gapsgt150mmbetweenrows
Slattedboxeslessrestrictivetoairflowwhencross-stackedifonly2wide
Allboxesatsameheight
oPtIMALAIrFLoWLoWrISKoFCondEnSAtIonGapslt150mmandsupplementaryfanstotargetlsquodeadspotsrsquo
Boxesstackedat90degtoairflowwith50mmgapsbetweenalternateboxeswithinrows
Allboxesatsameheightroofspaceventilatedheated
Loadingthestore
rEFrIGErAtIon
Fridgesystemsizeampperformance
Spaceventilationcoolingrate
Positiveventilationcoolingrate
dEHYdrAtIonrISK
Smallfridgecoilwithair-onair-offtempdifferencegt35degC
Longrunningtimesnoeffectivecooling
Asabove
Coolsatlt025degCday
Coolsatlt05degCday
Coolsatgt05degCday
Coolsatgt1degCday(ManagecondensationriskP11)
FrIdGESIZEoPtIMAL
Air-onair-offtemperaturedifference~25degC
Coolsat~05degCday
Coolsat~1degCday
Refrigeration
9S T O R E m a n a g E R S rsquo g U I D E
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
MonItorInGAndtrACEABILtY
temperaturesensors
Bulkstacksensorplacement
Condensationcontrol
Stockcontrol
Storerecording
LACKoFControL
Nosensorsinstore
Asabove
Asabove
Chemicalrecordsonlylegalminimum
Asabove
Inaironlycropconditionunknown
Topsurfaceonly-pronetoinfluencebyairabove
Controloftemperaturedifferentials
Chemicaluseplusstocklocationinstorerecorded
Occasionalmanualrecordingofstoretemperatures
1or2sensorsincropnomeasureoftemperaturevariation
Topandbaseofstacktomeasurepiletemperaturegradient
Relativehumiditymeasurementfordew-pointcontrol
Chemicalusestockdetailslabelledoneachbox
Regularmanualrecordingofstoretemperaturesandfanrunningtimes
FuLLCAPABILItY
1sensorper100tonnes
Ascolumn3butalso300mmdowntoanticipatecondensation
Skinresistancesensingtomeasureanywetting
Boxrecordsincludelocation-feedbackonstorageproblems
Automaticloggingofstoretemperaturesandfanrunningtimes
LoadingthestoreampStoremonitoringandqualityassurance
QCSAMPLInG Singlepointsampling Multi-pointsampling
ononelevelMulti-pointsamplingonmorethanonelevel
Comprehensivesamplingthroughoutthestore
Storageformarkets
SEEdGrAdInG
CondEnSAtIonrISK
Instore Nextdoorbutnoairlock
Nextdoorwithstripcurtain
StorEISoLAtEd
Nextdoorwithhighspeeddoor
Condensationonthecrop
10 S T O R E m a n a g E R S rsquo g U I D E
Fabricordoorleakagetowind-inducedventilationreducesthebenefitsofthestoreasitislikelytoleadtolossofenvironmentalcontrolcropweightlossandpossiblecondensationonthecropVentilationorrefrigerationrun-timewillincreasetocoolthecropwarmedbytheleakingair
ContainmentThecapitalcostofabulkstorewithload-bearinginsulatedretainingwallsishigherthanforaboxstoreButwhenthecapitalcostofboxesisaddedbulkstorageischeaperoverallBoxstoreseaseseparationfordifferentstocksandprovidemoreflexibilityforcropmovementandmarketingDeepbulkpilescanleadtopressurebruisingproblemsifthecropisstoredover40mhighorifexcessivelyventilatedbynon-humidifiedairBoxstorageisnormallyfreefrompressurebruisinganddependingontheirqualityboxescanbestackedupto8high
InsulationThequalityoftheinsulationwilldeterminetoalargeextenthowwellapotatostoreperformsInsulationisakeyfactorforapotatostoremuchmoresothanitisforgeneralpurposebuildings
MaintainingtemperaturesabovefreezingpointisseldomaproblemgiventhequantityofheatproducedinalargestoreHoweveranyheatthatleaksintoastorehastoberemovedbyexpendingenergyeitherintheformofventilationorrefrigerationInadditiontotheimplicationsoncosttheavoidableoperationofenvironmentalcontrol
2 Storagebuildings
Awellsealedandinsulatedpotatostore(Figure21)will
bullAllowthecroptobekeptatastabletemperaturelargelyunaffectedbydiurnalvariationandambientconditions
bullHelpmaintainarelativehumidityof90-100tominimisetuberweightloss
bullAllowcropstobestoredfreefromcondensationinchangeableweatherconditions
ControlledventilationControlledventilationallowscroprespirationheattoberemovedandthecroptobedriedandcooledFansarepositionedtocreateaflowofairthroughthecrop(positiveventilationbulkorbox)ortoformarollingmassofairthatwillflowoverthestackofboxesandthroughtheirpalletslots(spaceventilation)
Coolingcanbeachievedusingambientairandormechanicalcooling(refrigeration)Internalrecirculationofair(withoutcooling)canbeusedtoeliminatetemperaturevariationortodistributechemicalsforsproutsuppressionordiseasecontrol
AirflowshouldbeasuniformaspossiblethroughoutthestoretogiveevendryingandstablecroptemperaturesAwelldesignedstorewillhavebeenbalancedtoachieveuniformityofairflowatitstypicaloperatingconditionThismightincludefeaturessuchastaperedairductsorgraduatedlateraloutletstodeliversimilarquantitiesofairacrossthewholestore
Figure 21 A well sealed and insulated potato store
11S T O R E m a n a g E R S rsquo g U I D E
foundinpotatostoreswherecompositemetalpolyisocyanurate(PIR)sandwichpanelsareusedThesearecommonplacenowadaysfornewlybuiltstoresOthersystemsforupgradesofferatbestlittlemorethanavapourcheckThistendstolimitthechoiceofinsulationtoeithersprayorboardpolyurethaneoralternativelyexpandedextrudedpolystyreneboard
Specialistadviceshouldbesoughtforallaspectsofstoragebuildingdesign
equipmentwillalwaysincreasewaterlossfromthecropItisthereforejustasbeneficialtouseinsulationtolimitanyheatingressintothestoreasitistominimisetheeffectsofcoldweatherAlight-colouredreflectiveexternalsurfacewillreduceunwantedsolarradiationgains
NearlyallinsulationmaterialshavetheirperformancereducedsignificantlybyverysmallincreasesintheirmoisturecontentTheuseofvapourbarrierstoprotectinsulationisonlyeffectiveinthehighhumidityconditions
Storeassessment
bullUndertakeadetailedassessmentofyourstoreasdescribedinsection1
Balancedventilation
bullTheventilationsysteminastoreshouldbeinbalanceThismeansthatforoptimalperformancedesignfeaturesarerequiredndashegtaperedductsndashtooffsettheeffectsofpressuredropintheventilationsystemP8
doorsandlouvres
bullDoorsandlouvresaretheweakpointsoftheinsulationlsquoenvelopersquoMakesuretheycloseproperlyandstayclosedRegularpositiveactuationfromacontrollerisbeneficialforkeepingambientlouverswhicharesubjecttowindpressureclosed
Insulation
bullEnsurestoreinsulationisingoodconditionandeffective
bullWatchforsignsofcondensationwithinthestructurethatwilldegradetheinsulationvalueegdelaminatedinsulationboardswheremoisturehasgotinbehindthepanels
bullEnsureanynewbuildwithcompositeconstructionusesPIRpanelswhichareresistanttospreadofflameinthecoreintheeventoffire
ACTION POINTS
StorAGEBuILdInGS
Figure 22 Building envelope stabilises internal climate
12 S T O R E m a n a g E R S rsquo g U I D E
AllotherthingsbeingequalmoisturelossisafunctionofstorehumidityandairflowratePotatostoreswillusuallysettletoapproximately98relativehumidityandintheabsenceofahumidificationsystemthiswillbederivedbyevaporationofmoisturefromtubersInappropriatelyspecifiedrefrigerationunitscanexacerbatemoistureloss
dormancyFreshlyharvestedtubersusuallydonotsproutevenwhenconditionsareoptimalforsproutgrowthTheperiodoverwhichsproutgrowthisinhibitedbytuberphysiologyratherthanenvironmentalreasonsistermedthedormantperiodorsimplylsquodormancyrsquo
LargedifferencesindormancyoccurbetweenvarietiesWarmstoragetemperatureshaveadormancy-breakingeffectSelectionofvarietiesbydormancycharacteristicscanbeusefulforminimisingsprout-suppressantinputs
Dormancybreakistakenasthepointwhere50oftubershavesproutsof3mmormoreinlengthWarmdrysummerstendtoreducedormancy(inextremecasesleadingtosproutgrowthinthefieldbeforeharvest)whilecoolgrowingconditionswillgenerallyprolongitWaterlogginghasadormancy-breakingeffect
Woundhealing(curing)Wheretubershavebeensubjectedtowounding(egbyhandlingduringharvest)thetuberwillattempttohealthewoundndashaprocessinvolvingsuberisationandcell-divisionThespeedofthisprocesswhichisimportantforpreventingmoisturelossanddiseaseingressisaffectedbyanumberoffactorsTheseincludestoragetemperatureandhumiditywithwarmertemperaturesandhigherhumidityreducingthetimerequiredforwound-healing
Althougheffectivewound-healingisimportantconditionsthatareoptimalforcuringmayalsobesuitablefordiseasedevelopmentWherecropsareharvestedearlyundergoodconditionsorwherethestoragedurationislimitedsufficientcuringmayoccurduringtheperiodoverwhichcroptemperatureisreducedtotheholdingvalueP11
3 Cropphysiology
respirationPotatotubersarelivingorganismsandinstorecontinuetorespireandrespondtotheirenvironmentTheydosobyusingsugarsfromstarchinrespirationThisprocessconsumesoxygenandreleasescarbondioxideandsomeheatenergywhichimpactonstoragesystems
Respirationishighestatharvestandfallsrapidlytoabasallevelinthefirstweeksofstorage(Figure31)Respirationisgreaterinearly-liftedimmaturecropsthaninlate-liftedmaturecrops
Basalrespirationratedependspredominantlyonstoragetemperature(Figure32)Minimumrespirationrateisachievedataround5oCwiththerateincreasingaboveorbelowthistemperature
Handlingmechanicaldamageexposuretoethyleneandsproutingwillleadtoanincreaseinrespirationrate
EvaporationAlthoughsomemoistureislostintheprocessofrespirationmostislostbysimpleevaporationfromthetubersurfaceEffectivewound-healingandsproutcontrolisimportantinlimitingmoisturelossfromtubers
Figure 31 Respiration after lifting ndash early harvest
Figure 33 Moisture exchange between tuber skin and surrounding air in balance at ~98 relative humidity
Figure 32 Respiration in relation to storage temperature
1 2 3 4 5 6 7 8 9 10
Hea
t out
put (
Wto
nne)
35
0
5
10
15
20
25
30
Harvest date 9 September
Days after harvest
Harvest date 20 October
5 15 25
Rat
e of
resp
iratio
n (m
g C
O2k
ghr
)
12
0
2
4
6
8
10
Storage temperature (˚C)
13S T O R E m a n a g E R S rsquo g U I D E
ThisisaccomplishedsimplybyincreasingstoragetemperatureHoweverreconditioningleadstovariabilityinfrycolourandisthereforenotrecommendedasaroutinestoragepractice
PreconditioningmayalsobeusedtomaintainprocessingqualityHeretherearenodistinctcuringpull-downholdingperiodsandfrycolourorsugarcontentisusedtodeterminecropstoragetemperatureTemperaturereductiontoatargetholdingvalueonlyoccursprovidinggoodprocessingqualityismaintained
GreeningandglycoalkaloidsTubersexposedtolightwillturngreenwhichresultsfromthesynthesisofchlorophyllChlorophyllisitselfharmlessbutgreentubersaregenerallyrejectedbecausetheyhaveelevatedlevelsofglycoalkaloidsagroupofnaturaltoxicantspresentinpotatoes
TopreventgreeninginstorageexposuretolightshouldthereforebeminimisedalthoughtheneedtoseethecropclearlyandhealthandsafetyrequirementsP21willoverridethisduringloadingandsubsequentshortperiodswhenstoresareaccessedtobeinspectedorsampled
SugarsandconditioningPotatoescontainthreemainsugarsglucoseandfructose(monosaccharides)andsucrose(adisaccharide)AllthreesugarsaresweetandareimportantflavourcomponentsinwarepotatoesInpotatoesforprocessingthestoremanagerisprimarilyinterestedinthemonosaccharidesDuringprocessingthesereactwithothercomponentstoproducethebrowningwhichisassessedbymarketsasfrycolourAstoremanagersupplyingcropforprocessingmayalsobeinterestedinsucrosecontentAlthoughsucrosedoesnottakepartinbrowningreactionstrendsinsucroselevelsmaybeusedtohelpensurelowreducingsugarsandlightfrycolourduringstorage
VarietygrowthstageandstoragetemperatureareimportantindeterminingtubersugarcontentPotatoesexhibitlowtemperature-sweeteningwheresugarsaccumulatewithinthetuberastemperatureisreducedDuringstorageforprocessingtemperatureshouldthereforebemaintainedatthelowestlevelthatsafelymaintainsacceptablefrycolour
Forprocessingcropschangesinsugarcontent(andhencefrycolour)canbeachievedusingreconditioning
respiration
Thegreatertherespirationrateofthepotatoesthemorelikelyitisthatwarmairwillcondenseoncoolersurfacepotatoes
bullPositivelyventilatepotatoestoremoverespirationheattopreventsurfacecondensation
bullUsehighventilationratestopreventcondensationinheavilyrespiringearly-liftedorimmaturecropsP11
Evaporation
Moisturelossfrompotatoesduetoevaporationwilloccuriftherelativehumidity(RH)oftheairsurroundingthepotatoesislessthan98
bullKeepstorewell-sealedtominimiseweightloss
bullPreventuncontrolledexternalairingressasthisusuallyhasalowerRHthanthestorageenvironment
Sugars
Sugarsincreaseandfrycolourswilldarkenifpotatoesarestoredatcoldtemperatures
bullStorecropsforprocessingatc7-10degC
bullMonitorcold-storedpre-packpotatoesforeffectsofsugarincreaseontaste
bullIfunsurecheckstoragerequirementswithyourcustomer
ACTION POINTS
CroPPHYSIoLoGY
14 S T O R E m a n a g E R S rsquo g U I D E
Silverscurf Blackdot Skinspot dryrot Gangrene Softrot
moderateinfection
severeinfection
4 Controlofstoragediseases
DiseasecontrolisafundamentalcomponentofstoragemanagementMostdiseasesdonotoriginateinstoretheycomefromtwoprimarysourcestheseedorthesoilHowevermanyofthediseaseproblemsaffectingthepremiummarketscandeveloptosomedegreeinstoreandifnotcontrolledtheconsequencescanbecatastrophiceitherintermsofphysicalbreakdownofthecroporinlossofmarketvalueWhetherdiseasewilldevelopinstoreornot(Figure41)dependson
bullTheamountofinoculumusuallysporesorbacteriapresentonthetubersbullWhethermoisturenutrientsandtemperaturearesuitableforthediseasetogrowbullThenaturalresistanceofthetubertothediseaseorganism
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
15S T O R E m a n a g E R S rsquo g U I D E
Storemanagementallowsustoinfluencethisrelationshipparticularlyinrelationtothemicro-climatearoundthetubertocontroldiseasesduringstorage
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
Micro-climate Tuberresistance
Inoculum
Figure 41 Interaction between micro-climate and disease
notifiablediseases
SomediseasesarenotindigenousinBritainandtheirestablishmentwouldaffectthelong-termviabilityofthepotatoindustryIfsymptomsofeitherbrownrotorringrotaresuspectedthenimmediatecontactwithlocalDEFRAofficesorPlantHealthandSeedinspectorateisnecessaryVisitwwwdefragovukplanthphhtmemailplanthealthinfodefragsigovukortelephone01904455174toreportsuspectedcasesinEnglandandWalesInScotlandvisitwwwsasagovukplant_health
PreventativemeasuresexistGotowwwpotatoorguksafehaventolearnmoreaboutnationalschemesthatprotectseedandwarecrophealth
ringrotBrownrot
16 S T O R E m a n a g E R S rsquo g U I D E
Figure 52 Ensure dust and debris are removed from ducts
CrosscontaminationofsporesbetweenpotatostocksisinevitableFanventilationwithinthestoremayincreasethespeedofthismovementcomparedwithnaturalconvectionButtheairflowisabenefitasithelpskeepthecropfreefromcondensationpreventinganysporeswhichdosettlefromgerminating
MajordustmovementanddispersaloccurswhenforklifttrucksstirupdustonthefloorduringhandlingTheresultantdustcloudwillsettleontopofthecropwherethecondensationneededforgerminationismostlikelyIfgradingiscarriedoutwithinthestorethiswillalsocreateaconsiderabledustcloudwithsimilarconsequences
dustremovalSweepingwithabrushmovestheheavierdustparticlesalongthefloorwhilecreatingacloudoflighterparticleswhichincludesthemajorityofsporesVacuumingloosensandremovesallfractionsofdustandiffittedwithafinefilterwillremovemostharmfulsporesfromthestoreVacuumingisthereforemuchpreferredtosweeping
disinfectionRemovingdustandsquashedtuberswillremovethemajorityofinoculumpresentSomedustandsporeswillremainonthefloorwallsandraftersaswellasthefloorandsidesofpotatoboxesthemajorityofwhichcanberemovedbypowerwashingIftotalremovalofviablesporesisrequiredegforhighhealthcropsadisinfectantcanbeusedThisisparticularlyrelevantinstoreswheredamagerelateddiseasessuchasdryrothaveoccurred
5 Storehygiene
AcleanstorefreefromdiscardedtubersdustanddebrishasanumberofadvantagesItwillminimisecropinfectionimproveairflowcontributetoworkerhealthandcomfortandislikelytoimpressclientsandcustomers
SomesoilisinevitablybroughtintostorewiththeharvestedcropOncedrythisbecomesapotentialsourceofdustwhenthecropismovedIfthecropisfreeofdiseasewhenharvestedanditremainssooverthestorageperiodthenthedustwillbemainlymineralinnatureHoweverifthecropisdiseasedorbecomessoduringstoragethedustmaycontainlargequantitiesofsporeswhichwillbeasourceofinoculuminthepresentorfutureyears
dustdispersalConvectioncurrentscausedbyrespirationheatfromthecropwillcirculatedustandsporesthroughoutthestore
Figure 51 Vacuuming of potato store
17S T O R E m a n a g E R S rsquo g U I D E
StorEHYGIEnE
Post-storagecleaning
bullStore-cleaningshouldbeundertakenannuallyInboxstoresthisisbestcarriedoutimmediatelyafterthelastcrophasbeenremovedsocleanedboxescanbereturnedtostore
bullInayearfollowingcropinfectionbysilverscurforskinspotextrarigorouscleaningshouldbecarriedout
bullVacuumdirtanddebrisfromfloorsledgesbeamsandotherhorizontalsurfaces
bullWhereinsulationisdamagedorisroughandcollectsdustrepairandvacuum
bullOnlypowerhoseifinsulationismoisture-proof
Cleaningboxes
bullEnsurethatbox-tippersongradinglinesaredesignedtodischargethetotalboxcontentstogetridofmajorcontamination
bullUsepowerhosetocleanboxes
bullWherecleaningboxesisroutineconsidersettingupaconveyor-basedautomaticwashingsystem
bullPower-washboxesforhighhealthcrops
bullWherepossiblereturncleanedboxestostoreorkeepundercoverasthiscanextendboxlifeby70
Whentousedisinfectants
Forhighhealthseedcropsdisinfectantsmaybebeneficialespeciallyafteracontaminatedcropinthepreviousyear
bullUsedisinfectantmistfogorsprayaftervacuumingstore
bullSpraydisinfectboxeswhichhelddiseasedcropout-gradesorlsquobrockrsquo
bullFollowinggradingofdiseasedpotatoespower-washgradinglinethenspraywithdisinfectantwheregradinghighhealthcrops
bullAlwaysuseapprovedproductsandseekspecialistadvice
notesomedisinfectantsmaydamagestoreinsulationandelectricalfittingsndashconsulttheproductlabelbeforeuse
dailycleaning
bullVacuumthefloorparticularlyforkliftroutesandundergradersatleastonceaday
Gradinginstore
GradinginstoreislikelytoincreasetheamountofcontaminateddustinthestoreandthelikelihoodofambientairenteringthroughopendoorsDustprovidesdiseaseinoculumwhileambientairmaycausecondensationparticularlyonthetopsurfaceofboxesorpile
bullIdeallygradeinseparatebuildingwithaplasticstripdoorbetweenthestoreandgradingarea
bullIfgradinginstoreisunavoidableenclosepickersinwarmedcabinandfitadustcontrolsystemtotheline
bullFitdewpointtemperaturemonitortowarnofcondensationrisks
ACTION POINTS
LeavingboxesoutsidewillallowlighttokillviablesporesBoxesshouldnotbestackedmorethanfourboxeshighforsafetyandifstackedinpairsasmallgapbetweenrowswillallownatural(ultraviolet)lighttoreachonesideofeveryboxHoweveroutsidestackingcanreduceboxlifebyupto40
CleaningandenergyefficiencyMaintainingfansventilationandrefrigerationequipmentinacleanconditionwillhelpprolongtheirworkinglifeand
improvetheirworkingefficiencyEnsurethattemperatureandhumidityprobesarekeptcleanandinspectlouvresevaporatorsandcondensersIfnecessarycleanbyvacuumingorpowerwashingIfwashingtakecarearoundelectricalandmovingsystemsandensurethatanyresultingiceisremovedbydefrosting
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
7S T O R E m a n a g E R S rsquo g U I D E
bullringthedescriptionswhichmostcloselydescribeyourstorebullConsiderthefactorsandrisksthisself-assessmentidentifiesbulldecideonanyactionneededbullrefertotheappropriatesectionoftheguideorseekfurtherspecialistadvice
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
VEntILAtIon
Bulkstoresystem
Boxstoresystem
Boxstoreairdistribution
recirculation
HIGHrISKoFContAMInAtIonNofanopendooronly
Nofanopendooronly
Aroundboxesnosingleldquoairrollrdquoestablished
None
Fanslt002m3st
Fanslt002m3st
Spaceventilationformsrollofairpartviaboxapertures
Someairmovementbutnoairroll
Spaceventilationampfansge002m3st
Ascolumn2+rooffansorpositiveventilationwithtraditionalboxes
Intermittentlt002m3stLowratepartstore
PoSItIVEampFAStdrYInGFansge002m3st
Positiveventilationampfansge004m3st
Positiveventilationusingpurposedesignedboxes
Intermittentge002m3stLowratecontinuous
Ventilation
FAnSYStEMS
Fantype
Fanefficiency
Ventilationcontrol
Mixing
Inletairprotection
unControLLEdrISKtoCroP
Centrifugalfan
Oldagedfanwithbigstartingload
Onoffswitching
Manual
Nofrostthermostat
Axial(propellerstyle)
Modernfan(s)withpower-factorcorrection
Automaticswitchingofsinglemultiplefans
Autonoairmixing
Thermostattocutfanoffineventoffrost
Automatedaxialfans
High-efficiencyfansforlowrunningcost
Manualspeedcontrolofautomaticsinglemultiplefans
Auto+airmixing
Inlettemperaturecontrol
FuLLControLoFCooLInG
AxialfansforpositiveventilationSoftstarthigh-efficiencylownoisefans
Automatedvariablespeedcontroloffans
Auto+airmixingampdew-pointcontrol
Inlettemperature+condensationcontrol
Ventilation
8 S T O R E m a n a g E R S rsquo g U I D E
1 Storeself-assessment
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
BoXStACKInG
Spaceventilatedstores
Cross-stackedboxes(ieat90degtomainblock)
Boxheight
rEStrICtEdAIrFLoWrISKoFCondEnSAtIonBoxesstackedrandomly
Boxesstackedacrosspalletslotsofmainblock
Inconsistentstackingheightthroughoutstore
Gapsacrossstore(riskofshortcircuiting)
Boxescross-stackedawayfrommainblocktoallowairtoenterpalletapertures
Rowsateaves1boxlowercapacityeconomicsdictate
Gapsgt150mmbetweenrows
Slattedboxeslessrestrictivetoairflowwhencross-stackedifonly2wide
Allboxesatsameheight
oPtIMALAIrFLoWLoWrISKoFCondEnSAtIonGapslt150mmandsupplementaryfanstotargetlsquodeadspotsrsquo
Boxesstackedat90degtoairflowwith50mmgapsbetweenalternateboxeswithinrows
Allboxesatsameheightroofspaceventilatedheated
Loadingthestore
rEFrIGErAtIon
Fridgesystemsizeampperformance
Spaceventilationcoolingrate
Positiveventilationcoolingrate
dEHYdrAtIonrISK
Smallfridgecoilwithair-onair-offtempdifferencegt35degC
Longrunningtimesnoeffectivecooling
Asabove
Coolsatlt025degCday
Coolsatlt05degCday
Coolsatgt05degCday
Coolsatgt1degCday(ManagecondensationriskP11)
FrIdGESIZEoPtIMAL
Air-onair-offtemperaturedifference~25degC
Coolsat~05degCday
Coolsat~1degCday
Refrigeration
9S T O R E m a n a g E R S rsquo g U I D E
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
MonItorInGAndtrACEABILtY
temperaturesensors
Bulkstacksensorplacement
Condensationcontrol
Stockcontrol
Storerecording
LACKoFControL
Nosensorsinstore
Asabove
Asabove
Chemicalrecordsonlylegalminimum
Asabove
Inaironlycropconditionunknown
Topsurfaceonly-pronetoinfluencebyairabove
Controloftemperaturedifferentials
Chemicaluseplusstocklocationinstorerecorded
Occasionalmanualrecordingofstoretemperatures
1or2sensorsincropnomeasureoftemperaturevariation
Topandbaseofstacktomeasurepiletemperaturegradient
Relativehumiditymeasurementfordew-pointcontrol
Chemicalusestockdetailslabelledoneachbox
Regularmanualrecordingofstoretemperaturesandfanrunningtimes
FuLLCAPABILItY
1sensorper100tonnes
Ascolumn3butalso300mmdowntoanticipatecondensation
Skinresistancesensingtomeasureanywetting
Boxrecordsincludelocation-feedbackonstorageproblems
Automaticloggingofstoretemperaturesandfanrunningtimes
LoadingthestoreampStoremonitoringandqualityassurance
QCSAMPLInG Singlepointsampling Multi-pointsampling
ononelevelMulti-pointsamplingonmorethanonelevel
Comprehensivesamplingthroughoutthestore
Storageformarkets
SEEdGrAdInG
CondEnSAtIonrISK
Instore Nextdoorbutnoairlock
Nextdoorwithstripcurtain
StorEISoLAtEd
Nextdoorwithhighspeeddoor
Condensationonthecrop
10 S T O R E m a n a g E R S rsquo g U I D E
Fabricordoorleakagetowind-inducedventilationreducesthebenefitsofthestoreasitislikelytoleadtolossofenvironmentalcontrolcropweightlossandpossiblecondensationonthecropVentilationorrefrigerationrun-timewillincreasetocoolthecropwarmedbytheleakingair
ContainmentThecapitalcostofabulkstorewithload-bearinginsulatedretainingwallsishigherthanforaboxstoreButwhenthecapitalcostofboxesisaddedbulkstorageischeaperoverallBoxstoreseaseseparationfordifferentstocksandprovidemoreflexibilityforcropmovementandmarketingDeepbulkpilescanleadtopressurebruisingproblemsifthecropisstoredover40mhighorifexcessivelyventilatedbynon-humidifiedairBoxstorageisnormallyfreefrompressurebruisinganddependingontheirqualityboxescanbestackedupto8high
InsulationThequalityoftheinsulationwilldeterminetoalargeextenthowwellapotatostoreperformsInsulationisakeyfactorforapotatostoremuchmoresothanitisforgeneralpurposebuildings
MaintainingtemperaturesabovefreezingpointisseldomaproblemgiventhequantityofheatproducedinalargestoreHoweveranyheatthatleaksintoastorehastoberemovedbyexpendingenergyeitherintheformofventilationorrefrigerationInadditiontotheimplicationsoncosttheavoidableoperationofenvironmentalcontrol
2 Storagebuildings
Awellsealedandinsulatedpotatostore(Figure21)will
bullAllowthecroptobekeptatastabletemperaturelargelyunaffectedbydiurnalvariationandambientconditions
bullHelpmaintainarelativehumidityof90-100tominimisetuberweightloss
bullAllowcropstobestoredfreefromcondensationinchangeableweatherconditions
ControlledventilationControlledventilationallowscroprespirationheattoberemovedandthecroptobedriedandcooledFansarepositionedtocreateaflowofairthroughthecrop(positiveventilationbulkorbox)ortoformarollingmassofairthatwillflowoverthestackofboxesandthroughtheirpalletslots(spaceventilation)
Coolingcanbeachievedusingambientairandormechanicalcooling(refrigeration)Internalrecirculationofair(withoutcooling)canbeusedtoeliminatetemperaturevariationortodistributechemicalsforsproutsuppressionordiseasecontrol
AirflowshouldbeasuniformaspossiblethroughoutthestoretogiveevendryingandstablecroptemperaturesAwelldesignedstorewillhavebeenbalancedtoachieveuniformityofairflowatitstypicaloperatingconditionThismightincludefeaturessuchastaperedairductsorgraduatedlateraloutletstodeliversimilarquantitiesofairacrossthewholestore
Figure 21 A well sealed and insulated potato store
11S T O R E m a n a g E R S rsquo g U I D E
foundinpotatostoreswherecompositemetalpolyisocyanurate(PIR)sandwichpanelsareusedThesearecommonplacenowadaysfornewlybuiltstoresOthersystemsforupgradesofferatbestlittlemorethanavapourcheckThistendstolimitthechoiceofinsulationtoeithersprayorboardpolyurethaneoralternativelyexpandedextrudedpolystyreneboard
Specialistadviceshouldbesoughtforallaspectsofstoragebuildingdesign
equipmentwillalwaysincreasewaterlossfromthecropItisthereforejustasbeneficialtouseinsulationtolimitanyheatingressintothestoreasitistominimisetheeffectsofcoldweatherAlight-colouredreflectiveexternalsurfacewillreduceunwantedsolarradiationgains
NearlyallinsulationmaterialshavetheirperformancereducedsignificantlybyverysmallincreasesintheirmoisturecontentTheuseofvapourbarrierstoprotectinsulationisonlyeffectiveinthehighhumidityconditions
Storeassessment
bullUndertakeadetailedassessmentofyourstoreasdescribedinsection1
Balancedventilation
bullTheventilationsysteminastoreshouldbeinbalanceThismeansthatforoptimalperformancedesignfeaturesarerequiredndashegtaperedductsndashtooffsettheeffectsofpressuredropintheventilationsystemP8
doorsandlouvres
bullDoorsandlouvresaretheweakpointsoftheinsulationlsquoenvelopersquoMakesuretheycloseproperlyandstayclosedRegularpositiveactuationfromacontrollerisbeneficialforkeepingambientlouverswhicharesubjecttowindpressureclosed
Insulation
bullEnsurestoreinsulationisingoodconditionandeffective
bullWatchforsignsofcondensationwithinthestructurethatwilldegradetheinsulationvalueegdelaminatedinsulationboardswheremoisturehasgotinbehindthepanels
bullEnsureanynewbuildwithcompositeconstructionusesPIRpanelswhichareresistanttospreadofflameinthecoreintheeventoffire
ACTION POINTS
StorAGEBuILdInGS
Figure 22 Building envelope stabilises internal climate
12 S T O R E m a n a g E R S rsquo g U I D E
AllotherthingsbeingequalmoisturelossisafunctionofstorehumidityandairflowratePotatostoreswillusuallysettletoapproximately98relativehumidityandintheabsenceofahumidificationsystemthiswillbederivedbyevaporationofmoisturefromtubersInappropriatelyspecifiedrefrigerationunitscanexacerbatemoistureloss
dormancyFreshlyharvestedtubersusuallydonotsproutevenwhenconditionsareoptimalforsproutgrowthTheperiodoverwhichsproutgrowthisinhibitedbytuberphysiologyratherthanenvironmentalreasonsistermedthedormantperiodorsimplylsquodormancyrsquo
LargedifferencesindormancyoccurbetweenvarietiesWarmstoragetemperatureshaveadormancy-breakingeffectSelectionofvarietiesbydormancycharacteristicscanbeusefulforminimisingsprout-suppressantinputs
Dormancybreakistakenasthepointwhere50oftubershavesproutsof3mmormoreinlengthWarmdrysummerstendtoreducedormancy(inextremecasesleadingtosproutgrowthinthefieldbeforeharvest)whilecoolgrowingconditionswillgenerallyprolongitWaterlogginghasadormancy-breakingeffect
Woundhealing(curing)Wheretubershavebeensubjectedtowounding(egbyhandlingduringharvest)thetuberwillattempttohealthewoundndashaprocessinvolvingsuberisationandcell-divisionThespeedofthisprocesswhichisimportantforpreventingmoisturelossanddiseaseingressisaffectedbyanumberoffactorsTheseincludestoragetemperatureandhumiditywithwarmertemperaturesandhigherhumidityreducingthetimerequiredforwound-healing
Althougheffectivewound-healingisimportantconditionsthatareoptimalforcuringmayalsobesuitablefordiseasedevelopmentWherecropsareharvestedearlyundergoodconditionsorwherethestoragedurationislimitedsufficientcuringmayoccurduringtheperiodoverwhichcroptemperatureisreducedtotheholdingvalueP11
3 Cropphysiology
respirationPotatotubersarelivingorganismsandinstorecontinuetorespireandrespondtotheirenvironmentTheydosobyusingsugarsfromstarchinrespirationThisprocessconsumesoxygenandreleasescarbondioxideandsomeheatenergywhichimpactonstoragesystems
Respirationishighestatharvestandfallsrapidlytoabasallevelinthefirstweeksofstorage(Figure31)Respirationisgreaterinearly-liftedimmaturecropsthaninlate-liftedmaturecrops
Basalrespirationratedependspredominantlyonstoragetemperature(Figure32)Minimumrespirationrateisachievedataround5oCwiththerateincreasingaboveorbelowthistemperature
Handlingmechanicaldamageexposuretoethyleneandsproutingwillleadtoanincreaseinrespirationrate
EvaporationAlthoughsomemoistureislostintheprocessofrespirationmostislostbysimpleevaporationfromthetubersurfaceEffectivewound-healingandsproutcontrolisimportantinlimitingmoisturelossfromtubers
Figure 31 Respiration after lifting ndash early harvest
Figure 33 Moisture exchange between tuber skin and surrounding air in balance at ~98 relative humidity
Figure 32 Respiration in relation to storage temperature
1 2 3 4 5 6 7 8 9 10
Hea
t out
put (
Wto
nne)
35
0
5
10
15
20
25
30
Harvest date 9 September
Days after harvest
Harvest date 20 October
5 15 25
Rat
e of
resp
iratio
n (m
g C
O2k
ghr
)
12
0
2
4
6
8
10
Storage temperature (˚C)
13S T O R E m a n a g E R S rsquo g U I D E
ThisisaccomplishedsimplybyincreasingstoragetemperatureHoweverreconditioningleadstovariabilityinfrycolourandisthereforenotrecommendedasaroutinestoragepractice
PreconditioningmayalsobeusedtomaintainprocessingqualityHeretherearenodistinctcuringpull-downholdingperiodsandfrycolourorsugarcontentisusedtodeterminecropstoragetemperatureTemperaturereductiontoatargetholdingvalueonlyoccursprovidinggoodprocessingqualityismaintained
GreeningandglycoalkaloidsTubersexposedtolightwillturngreenwhichresultsfromthesynthesisofchlorophyllChlorophyllisitselfharmlessbutgreentubersaregenerallyrejectedbecausetheyhaveelevatedlevelsofglycoalkaloidsagroupofnaturaltoxicantspresentinpotatoes
TopreventgreeninginstorageexposuretolightshouldthereforebeminimisedalthoughtheneedtoseethecropclearlyandhealthandsafetyrequirementsP21willoverridethisduringloadingandsubsequentshortperiodswhenstoresareaccessedtobeinspectedorsampled
SugarsandconditioningPotatoescontainthreemainsugarsglucoseandfructose(monosaccharides)andsucrose(adisaccharide)AllthreesugarsaresweetandareimportantflavourcomponentsinwarepotatoesInpotatoesforprocessingthestoremanagerisprimarilyinterestedinthemonosaccharidesDuringprocessingthesereactwithothercomponentstoproducethebrowningwhichisassessedbymarketsasfrycolourAstoremanagersupplyingcropforprocessingmayalsobeinterestedinsucrosecontentAlthoughsucrosedoesnottakepartinbrowningreactionstrendsinsucroselevelsmaybeusedtohelpensurelowreducingsugarsandlightfrycolourduringstorage
VarietygrowthstageandstoragetemperatureareimportantindeterminingtubersugarcontentPotatoesexhibitlowtemperature-sweeteningwheresugarsaccumulatewithinthetuberastemperatureisreducedDuringstorageforprocessingtemperatureshouldthereforebemaintainedatthelowestlevelthatsafelymaintainsacceptablefrycolour
Forprocessingcropschangesinsugarcontent(andhencefrycolour)canbeachievedusingreconditioning
respiration
Thegreatertherespirationrateofthepotatoesthemorelikelyitisthatwarmairwillcondenseoncoolersurfacepotatoes
bullPositivelyventilatepotatoestoremoverespirationheattopreventsurfacecondensation
bullUsehighventilationratestopreventcondensationinheavilyrespiringearly-liftedorimmaturecropsP11
Evaporation
Moisturelossfrompotatoesduetoevaporationwilloccuriftherelativehumidity(RH)oftheairsurroundingthepotatoesislessthan98
bullKeepstorewell-sealedtominimiseweightloss
bullPreventuncontrolledexternalairingressasthisusuallyhasalowerRHthanthestorageenvironment
Sugars
Sugarsincreaseandfrycolourswilldarkenifpotatoesarestoredatcoldtemperatures
bullStorecropsforprocessingatc7-10degC
bullMonitorcold-storedpre-packpotatoesforeffectsofsugarincreaseontaste
bullIfunsurecheckstoragerequirementswithyourcustomer
ACTION POINTS
CroPPHYSIoLoGY
14 S T O R E m a n a g E R S rsquo g U I D E
Silverscurf Blackdot Skinspot dryrot Gangrene Softrot
moderateinfection
severeinfection
4 Controlofstoragediseases
DiseasecontrolisafundamentalcomponentofstoragemanagementMostdiseasesdonotoriginateinstoretheycomefromtwoprimarysourcestheseedorthesoilHowevermanyofthediseaseproblemsaffectingthepremiummarketscandeveloptosomedegreeinstoreandifnotcontrolledtheconsequencescanbecatastrophiceitherintermsofphysicalbreakdownofthecroporinlossofmarketvalueWhetherdiseasewilldevelopinstoreornot(Figure41)dependson
bullTheamountofinoculumusuallysporesorbacteriapresentonthetubersbullWhethermoisturenutrientsandtemperaturearesuitableforthediseasetogrowbullThenaturalresistanceofthetubertothediseaseorganism
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
15S T O R E m a n a g E R S rsquo g U I D E
Storemanagementallowsustoinfluencethisrelationshipparticularlyinrelationtothemicro-climatearoundthetubertocontroldiseasesduringstorage
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
Micro-climate Tuberresistance
Inoculum
Figure 41 Interaction between micro-climate and disease
notifiablediseases
SomediseasesarenotindigenousinBritainandtheirestablishmentwouldaffectthelong-termviabilityofthepotatoindustryIfsymptomsofeitherbrownrotorringrotaresuspectedthenimmediatecontactwithlocalDEFRAofficesorPlantHealthandSeedinspectorateisnecessaryVisitwwwdefragovukplanthphhtmemailplanthealthinfodefragsigovukortelephone01904455174toreportsuspectedcasesinEnglandandWalesInScotlandvisitwwwsasagovukplant_health
PreventativemeasuresexistGotowwwpotatoorguksafehaventolearnmoreaboutnationalschemesthatprotectseedandwarecrophealth
ringrotBrownrot
16 S T O R E m a n a g E R S rsquo g U I D E
Figure 52 Ensure dust and debris are removed from ducts
CrosscontaminationofsporesbetweenpotatostocksisinevitableFanventilationwithinthestoremayincreasethespeedofthismovementcomparedwithnaturalconvectionButtheairflowisabenefitasithelpskeepthecropfreefromcondensationpreventinganysporeswhichdosettlefromgerminating
MajordustmovementanddispersaloccurswhenforklifttrucksstirupdustonthefloorduringhandlingTheresultantdustcloudwillsettleontopofthecropwherethecondensationneededforgerminationismostlikelyIfgradingiscarriedoutwithinthestorethiswillalsocreateaconsiderabledustcloudwithsimilarconsequences
dustremovalSweepingwithabrushmovestheheavierdustparticlesalongthefloorwhilecreatingacloudoflighterparticleswhichincludesthemajorityofsporesVacuumingloosensandremovesallfractionsofdustandiffittedwithafinefilterwillremovemostharmfulsporesfromthestoreVacuumingisthereforemuchpreferredtosweeping
disinfectionRemovingdustandsquashedtuberswillremovethemajorityofinoculumpresentSomedustandsporeswillremainonthefloorwallsandraftersaswellasthefloorandsidesofpotatoboxesthemajorityofwhichcanberemovedbypowerwashingIftotalremovalofviablesporesisrequiredegforhighhealthcropsadisinfectantcanbeusedThisisparticularlyrelevantinstoreswheredamagerelateddiseasessuchasdryrothaveoccurred
5 Storehygiene
AcleanstorefreefromdiscardedtubersdustanddebrishasanumberofadvantagesItwillminimisecropinfectionimproveairflowcontributetoworkerhealthandcomfortandislikelytoimpressclientsandcustomers
SomesoilisinevitablybroughtintostorewiththeharvestedcropOncedrythisbecomesapotentialsourceofdustwhenthecropismovedIfthecropisfreeofdiseasewhenharvestedanditremainssooverthestorageperiodthenthedustwillbemainlymineralinnatureHoweverifthecropisdiseasedorbecomessoduringstoragethedustmaycontainlargequantitiesofsporeswhichwillbeasourceofinoculuminthepresentorfutureyears
dustdispersalConvectioncurrentscausedbyrespirationheatfromthecropwillcirculatedustandsporesthroughoutthestore
Figure 51 Vacuuming of potato store
17S T O R E m a n a g E R S rsquo g U I D E
StorEHYGIEnE
Post-storagecleaning
bullStore-cleaningshouldbeundertakenannuallyInboxstoresthisisbestcarriedoutimmediatelyafterthelastcrophasbeenremovedsocleanedboxescanbereturnedtostore
bullInayearfollowingcropinfectionbysilverscurforskinspotextrarigorouscleaningshouldbecarriedout
bullVacuumdirtanddebrisfromfloorsledgesbeamsandotherhorizontalsurfaces
bullWhereinsulationisdamagedorisroughandcollectsdustrepairandvacuum
bullOnlypowerhoseifinsulationismoisture-proof
Cleaningboxes
bullEnsurethatbox-tippersongradinglinesaredesignedtodischargethetotalboxcontentstogetridofmajorcontamination
bullUsepowerhosetocleanboxes
bullWherecleaningboxesisroutineconsidersettingupaconveyor-basedautomaticwashingsystem
bullPower-washboxesforhighhealthcrops
bullWherepossiblereturncleanedboxestostoreorkeepundercoverasthiscanextendboxlifeby70
Whentousedisinfectants
Forhighhealthseedcropsdisinfectantsmaybebeneficialespeciallyafteracontaminatedcropinthepreviousyear
bullUsedisinfectantmistfogorsprayaftervacuumingstore
bullSpraydisinfectboxeswhichhelddiseasedcropout-gradesorlsquobrockrsquo
bullFollowinggradingofdiseasedpotatoespower-washgradinglinethenspraywithdisinfectantwheregradinghighhealthcrops
bullAlwaysuseapprovedproductsandseekspecialistadvice
notesomedisinfectantsmaydamagestoreinsulationandelectricalfittingsndashconsulttheproductlabelbeforeuse
dailycleaning
bullVacuumthefloorparticularlyforkliftroutesandundergradersatleastonceaday
Gradinginstore
GradinginstoreislikelytoincreasetheamountofcontaminateddustinthestoreandthelikelihoodofambientairenteringthroughopendoorsDustprovidesdiseaseinoculumwhileambientairmaycausecondensationparticularlyonthetopsurfaceofboxesorpile
bullIdeallygradeinseparatebuildingwithaplasticstripdoorbetweenthestoreandgradingarea
bullIfgradinginstoreisunavoidableenclosepickersinwarmedcabinandfitadustcontrolsystemtotheline
bullFitdewpointtemperaturemonitortowarnofcondensationrisks
ACTION POINTS
LeavingboxesoutsidewillallowlighttokillviablesporesBoxesshouldnotbestackedmorethanfourboxeshighforsafetyandifstackedinpairsasmallgapbetweenrowswillallownatural(ultraviolet)lighttoreachonesideofeveryboxHoweveroutsidestackingcanreduceboxlifebyupto40
CleaningandenergyefficiencyMaintainingfansventilationandrefrigerationequipmentinacleanconditionwillhelpprolongtheirworkinglifeand
improvetheirworkingefficiencyEnsurethattemperatureandhumidityprobesarekeptcleanandinspectlouvresevaporatorsandcondensersIfnecessarycleanbyvacuumingorpowerwashingIfwashingtakecarearoundelectricalandmovingsystemsandensurethatanyresultingiceisremovedbydefrosting
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
8 S T O R E m a n a g E R S rsquo g U I D E
1 Storeself-assessment
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
BoXStACKInG
Spaceventilatedstores
Cross-stackedboxes(ieat90degtomainblock)
Boxheight
rEStrICtEdAIrFLoWrISKoFCondEnSAtIonBoxesstackedrandomly
Boxesstackedacrosspalletslotsofmainblock
Inconsistentstackingheightthroughoutstore
Gapsacrossstore(riskofshortcircuiting)
Boxescross-stackedawayfrommainblocktoallowairtoenterpalletapertures
Rowsateaves1boxlowercapacityeconomicsdictate
Gapsgt150mmbetweenrows
Slattedboxeslessrestrictivetoairflowwhencross-stackedifonly2wide
Allboxesatsameheight
oPtIMALAIrFLoWLoWrISKoFCondEnSAtIonGapslt150mmandsupplementaryfanstotargetlsquodeadspotsrsquo
Boxesstackedat90degtoairflowwith50mmgapsbetweenalternateboxeswithinrows
Allboxesatsameheightroofspaceventilatedheated
Loadingthestore
rEFrIGErAtIon
Fridgesystemsizeampperformance
Spaceventilationcoolingrate
Positiveventilationcoolingrate
dEHYdrAtIonrISK
Smallfridgecoilwithair-onair-offtempdifferencegt35degC
Longrunningtimesnoeffectivecooling
Asabove
Coolsatlt025degCday
Coolsatlt05degCday
Coolsatgt05degCday
Coolsatgt1degCday(ManagecondensationriskP11)
FrIdGESIZEoPtIMAL
Air-onair-offtemperaturedifference~25degC
Coolsat~05degCday
Coolsat~1degCday
Refrigeration
9S T O R E m a n a g E R S rsquo g U I D E
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
MonItorInGAndtrACEABILtY
temperaturesensors
Bulkstacksensorplacement
Condensationcontrol
Stockcontrol
Storerecording
LACKoFControL
Nosensorsinstore
Asabove
Asabove
Chemicalrecordsonlylegalminimum
Asabove
Inaironlycropconditionunknown
Topsurfaceonly-pronetoinfluencebyairabove
Controloftemperaturedifferentials
Chemicaluseplusstocklocationinstorerecorded
Occasionalmanualrecordingofstoretemperatures
1or2sensorsincropnomeasureoftemperaturevariation
Topandbaseofstacktomeasurepiletemperaturegradient
Relativehumiditymeasurementfordew-pointcontrol
Chemicalusestockdetailslabelledoneachbox
Regularmanualrecordingofstoretemperaturesandfanrunningtimes
FuLLCAPABILItY
1sensorper100tonnes
Ascolumn3butalso300mmdowntoanticipatecondensation
Skinresistancesensingtomeasureanywetting
Boxrecordsincludelocation-feedbackonstorageproblems
Automaticloggingofstoretemperaturesandfanrunningtimes
LoadingthestoreampStoremonitoringandqualityassurance
QCSAMPLInG Singlepointsampling Multi-pointsampling
ononelevelMulti-pointsamplingonmorethanonelevel
Comprehensivesamplingthroughoutthestore
Storageformarkets
SEEdGrAdInG
CondEnSAtIonrISK
Instore Nextdoorbutnoairlock
Nextdoorwithstripcurtain
StorEISoLAtEd
Nextdoorwithhighspeeddoor
Condensationonthecrop
10 S T O R E m a n a g E R S rsquo g U I D E
Fabricordoorleakagetowind-inducedventilationreducesthebenefitsofthestoreasitislikelytoleadtolossofenvironmentalcontrolcropweightlossandpossiblecondensationonthecropVentilationorrefrigerationrun-timewillincreasetocoolthecropwarmedbytheleakingair
ContainmentThecapitalcostofabulkstorewithload-bearinginsulatedretainingwallsishigherthanforaboxstoreButwhenthecapitalcostofboxesisaddedbulkstorageischeaperoverallBoxstoreseaseseparationfordifferentstocksandprovidemoreflexibilityforcropmovementandmarketingDeepbulkpilescanleadtopressurebruisingproblemsifthecropisstoredover40mhighorifexcessivelyventilatedbynon-humidifiedairBoxstorageisnormallyfreefrompressurebruisinganddependingontheirqualityboxescanbestackedupto8high
InsulationThequalityoftheinsulationwilldeterminetoalargeextenthowwellapotatostoreperformsInsulationisakeyfactorforapotatostoremuchmoresothanitisforgeneralpurposebuildings
MaintainingtemperaturesabovefreezingpointisseldomaproblemgiventhequantityofheatproducedinalargestoreHoweveranyheatthatleaksintoastorehastoberemovedbyexpendingenergyeitherintheformofventilationorrefrigerationInadditiontotheimplicationsoncosttheavoidableoperationofenvironmentalcontrol
2 Storagebuildings
Awellsealedandinsulatedpotatostore(Figure21)will
bullAllowthecroptobekeptatastabletemperaturelargelyunaffectedbydiurnalvariationandambientconditions
bullHelpmaintainarelativehumidityof90-100tominimisetuberweightloss
bullAllowcropstobestoredfreefromcondensationinchangeableweatherconditions
ControlledventilationControlledventilationallowscroprespirationheattoberemovedandthecroptobedriedandcooledFansarepositionedtocreateaflowofairthroughthecrop(positiveventilationbulkorbox)ortoformarollingmassofairthatwillflowoverthestackofboxesandthroughtheirpalletslots(spaceventilation)
Coolingcanbeachievedusingambientairandormechanicalcooling(refrigeration)Internalrecirculationofair(withoutcooling)canbeusedtoeliminatetemperaturevariationortodistributechemicalsforsproutsuppressionordiseasecontrol
AirflowshouldbeasuniformaspossiblethroughoutthestoretogiveevendryingandstablecroptemperaturesAwelldesignedstorewillhavebeenbalancedtoachieveuniformityofairflowatitstypicaloperatingconditionThismightincludefeaturessuchastaperedairductsorgraduatedlateraloutletstodeliversimilarquantitiesofairacrossthewholestore
Figure 21 A well sealed and insulated potato store
11S T O R E m a n a g E R S rsquo g U I D E
foundinpotatostoreswherecompositemetalpolyisocyanurate(PIR)sandwichpanelsareusedThesearecommonplacenowadaysfornewlybuiltstoresOthersystemsforupgradesofferatbestlittlemorethanavapourcheckThistendstolimitthechoiceofinsulationtoeithersprayorboardpolyurethaneoralternativelyexpandedextrudedpolystyreneboard
Specialistadviceshouldbesoughtforallaspectsofstoragebuildingdesign
equipmentwillalwaysincreasewaterlossfromthecropItisthereforejustasbeneficialtouseinsulationtolimitanyheatingressintothestoreasitistominimisetheeffectsofcoldweatherAlight-colouredreflectiveexternalsurfacewillreduceunwantedsolarradiationgains
NearlyallinsulationmaterialshavetheirperformancereducedsignificantlybyverysmallincreasesintheirmoisturecontentTheuseofvapourbarrierstoprotectinsulationisonlyeffectiveinthehighhumidityconditions
Storeassessment
bullUndertakeadetailedassessmentofyourstoreasdescribedinsection1
Balancedventilation
bullTheventilationsysteminastoreshouldbeinbalanceThismeansthatforoptimalperformancedesignfeaturesarerequiredndashegtaperedductsndashtooffsettheeffectsofpressuredropintheventilationsystemP8
doorsandlouvres
bullDoorsandlouvresaretheweakpointsoftheinsulationlsquoenvelopersquoMakesuretheycloseproperlyandstayclosedRegularpositiveactuationfromacontrollerisbeneficialforkeepingambientlouverswhicharesubjecttowindpressureclosed
Insulation
bullEnsurestoreinsulationisingoodconditionandeffective
bullWatchforsignsofcondensationwithinthestructurethatwilldegradetheinsulationvalueegdelaminatedinsulationboardswheremoisturehasgotinbehindthepanels
bullEnsureanynewbuildwithcompositeconstructionusesPIRpanelswhichareresistanttospreadofflameinthecoreintheeventoffire
ACTION POINTS
StorAGEBuILdInGS
Figure 22 Building envelope stabilises internal climate
12 S T O R E m a n a g E R S rsquo g U I D E
AllotherthingsbeingequalmoisturelossisafunctionofstorehumidityandairflowratePotatostoreswillusuallysettletoapproximately98relativehumidityandintheabsenceofahumidificationsystemthiswillbederivedbyevaporationofmoisturefromtubersInappropriatelyspecifiedrefrigerationunitscanexacerbatemoistureloss
dormancyFreshlyharvestedtubersusuallydonotsproutevenwhenconditionsareoptimalforsproutgrowthTheperiodoverwhichsproutgrowthisinhibitedbytuberphysiologyratherthanenvironmentalreasonsistermedthedormantperiodorsimplylsquodormancyrsquo
LargedifferencesindormancyoccurbetweenvarietiesWarmstoragetemperatureshaveadormancy-breakingeffectSelectionofvarietiesbydormancycharacteristicscanbeusefulforminimisingsprout-suppressantinputs
Dormancybreakistakenasthepointwhere50oftubershavesproutsof3mmormoreinlengthWarmdrysummerstendtoreducedormancy(inextremecasesleadingtosproutgrowthinthefieldbeforeharvest)whilecoolgrowingconditionswillgenerallyprolongitWaterlogginghasadormancy-breakingeffect
Woundhealing(curing)Wheretubershavebeensubjectedtowounding(egbyhandlingduringharvest)thetuberwillattempttohealthewoundndashaprocessinvolvingsuberisationandcell-divisionThespeedofthisprocesswhichisimportantforpreventingmoisturelossanddiseaseingressisaffectedbyanumberoffactorsTheseincludestoragetemperatureandhumiditywithwarmertemperaturesandhigherhumidityreducingthetimerequiredforwound-healing
Althougheffectivewound-healingisimportantconditionsthatareoptimalforcuringmayalsobesuitablefordiseasedevelopmentWherecropsareharvestedearlyundergoodconditionsorwherethestoragedurationislimitedsufficientcuringmayoccurduringtheperiodoverwhichcroptemperatureisreducedtotheholdingvalueP11
3 Cropphysiology
respirationPotatotubersarelivingorganismsandinstorecontinuetorespireandrespondtotheirenvironmentTheydosobyusingsugarsfromstarchinrespirationThisprocessconsumesoxygenandreleasescarbondioxideandsomeheatenergywhichimpactonstoragesystems
Respirationishighestatharvestandfallsrapidlytoabasallevelinthefirstweeksofstorage(Figure31)Respirationisgreaterinearly-liftedimmaturecropsthaninlate-liftedmaturecrops
Basalrespirationratedependspredominantlyonstoragetemperature(Figure32)Minimumrespirationrateisachievedataround5oCwiththerateincreasingaboveorbelowthistemperature
Handlingmechanicaldamageexposuretoethyleneandsproutingwillleadtoanincreaseinrespirationrate
EvaporationAlthoughsomemoistureislostintheprocessofrespirationmostislostbysimpleevaporationfromthetubersurfaceEffectivewound-healingandsproutcontrolisimportantinlimitingmoisturelossfromtubers
Figure 31 Respiration after lifting ndash early harvest
Figure 33 Moisture exchange between tuber skin and surrounding air in balance at ~98 relative humidity
Figure 32 Respiration in relation to storage temperature
1 2 3 4 5 6 7 8 9 10
Hea
t out
put (
Wto
nne)
35
0
5
10
15
20
25
30
Harvest date 9 September
Days after harvest
Harvest date 20 October
5 15 25
Rat
e of
resp
iratio
n (m
g C
O2k
ghr
)
12
0
2
4
6
8
10
Storage temperature (˚C)
13S T O R E m a n a g E R S rsquo g U I D E
ThisisaccomplishedsimplybyincreasingstoragetemperatureHoweverreconditioningleadstovariabilityinfrycolourandisthereforenotrecommendedasaroutinestoragepractice
PreconditioningmayalsobeusedtomaintainprocessingqualityHeretherearenodistinctcuringpull-downholdingperiodsandfrycolourorsugarcontentisusedtodeterminecropstoragetemperatureTemperaturereductiontoatargetholdingvalueonlyoccursprovidinggoodprocessingqualityismaintained
GreeningandglycoalkaloidsTubersexposedtolightwillturngreenwhichresultsfromthesynthesisofchlorophyllChlorophyllisitselfharmlessbutgreentubersaregenerallyrejectedbecausetheyhaveelevatedlevelsofglycoalkaloidsagroupofnaturaltoxicantspresentinpotatoes
TopreventgreeninginstorageexposuretolightshouldthereforebeminimisedalthoughtheneedtoseethecropclearlyandhealthandsafetyrequirementsP21willoverridethisduringloadingandsubsequentshortperiodswhenstoresareaccessedtobeinspectedorsampled
SugarsandconditioningPotatoescontainthreemainsugarsglucoseandfructose(monosaccharides)andsucrose(adisaccharide)AllthreesugarsaresweetandareimportantflavourcomponentsinwarepotatoesInpotatoesforprocessingthestoremanagerisprimarilyinterestedinthemonosaccharidesDuringprocessingthesereactwithothercomponentstoproducethebrowningwhichisassessedbymarketsasfrycolourAstoremanagersupplyingcropforprocessingmayalsobeinterestedinsucrosecontentAlthoughsucrosedoesnottakepartinbrowningreactionstrendsinsucroselevelsmaybeusedtohelpensurelowreducingsugarsandlightfrycolourduringstorage
VarietygrowthstageandstoragetemperatureareimportantindeterminingtubersugarcontentPotatoesexhibitlowtemperature-sweeteningwheresugarsaccumulatewithinthetuberastemperatureisreducedDuringstorageforprocessingtemperatureshouldthereforebemaintainedatthelowestlevelthatsafelymaintainsacceptablefrycolour
Forprocessingcropschangesinsugarcontent(andhencefrycolour)canbeachievedusingreconditioning
respiration
Thegreatertherespirationrateofthepotatoesthemorelikelyitisthatwarmairwillcondenseoncoolersurfacepotatoes
bullPositivelyventilatepotatoestoremoverespirationheattopreventsurfacecondensation
bullUsehighventilationratestopreventcondensationinheavilyrespiringearly-liftedorimmaturecropsP11
Evaporation
Moisturelossfrompotatoesduetoevaporationwilloccuriftherelativehumidity(RH)oftheairsurroundingthepotatoesislessthan98
bullKeepstorewell-sealedtominimiseweightloss
bullPreventuncontrolledexternalairingressasthisusuallyhasalowerRHthanthestorageenvironment
Sugars
Sugarsincreaseandfrycolourswilldarkenifpotatoesarestoredatcoldtemperatures
bullStorecropsforprocessingatc7-10degC
bullMonitorcold-storedpre-packpotatoesforeffectsofsugarincreaseontaste
bullIfunsurecheckstoragerequirementswithyourcustomer
ACTION POINTS
CroPPHYSIoLoGY
14 S T O R E m a n a g E R S rsquo g U I D E
Silverscurf Blackdot Skinspot dryrot Gangrene Softrot
moderateinfection
severeinfection
4 Controlofstoragediseases
DiseasecontrolisafundamentalcomponentofstoragemanagementMostdiseasesdonotoriginateinstoretheycomefromtwoprimarysourcestheseedorthesoilHowevermanyofthediseaseproblemsaffectingthepremiummarketscandeveloptosomedegreeinstoreandifnotcontrolledtheconsequencescanbecatastrophiceitherintermsofphysicalbreakdownofthecroporinlossofmarketvalueWhetherdiseasewilldevelopinstoreornot(Figure41)dependson
bullTheamountofinoculumusuallysporesorbacteriapresentonthetubersbullWhethermoisturenutrientsandtemperaturearesuitableforthediseasetogrowbullThenaturalresistanceofthetubertothediseaseorganism
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
15S T O R E m a n a g E R S rsquo g U I D E
Storemanagementallowsustoinfluencethisrelationshipparticularlyinrelationtothemicro-climatearoundthetubertocontroldiseasesduringstorage
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
Micro-climate Tuberresistance
Inoculum
Figure 41 Interaction between micro-climate and disease
notifiablediseases
SomediseasesarenotindigenousinBritainandtheirestablishmentwouldaffectthelong-termviabilityofthepotatoindustryIfsymptomsofeitherbrownrotorringrotaresuspectedthenimmediatecontactwithlocalDEFRAofficesorPlantHealthandSeedinspectorateisnecessaryVisitwwwdefragovukplanthphhtmemailplanthealthinfodefragsigovukortelephone01904455174toreportsuspectedcasesinEnglandandWalesInScotlandvisitwwwsasagovukplant_health
PreventativemeasuresexistGotowwwpotatoorguksafehaventolearnmoreaboutnationalschemesthatprotectseedandwarecrophealth
ringrotBrownrot
16 S T O R E m a n a g E R S rsquo g U I D E
Figure 52 Ensure dust and debris are removed from ducts
CrosscontaminationofsporesbetweenpotatostocksisinevitableFanventilationwithinthestoremayincreasethespeedofthismovementcomparedwithnaturalconvectionButtheairflowisabenefitasithelpskeepthecropfreefromcondensationpreventinganysporeswhichdosettlefromgerminating
MajordustmovementanddispersaloccurswhenforklifttrucksstirupdustonthefloorduringhandlingTheresultantdustcloudwillsettleontopofthecropwherethecondensationneededforgerminationismostlikelyIfgradingiscarriedoutwithinthestorethiswillalsocreateaconsiderabledustcloudwithsimilarconsequences
dustremovalSweepingwithabrushmovestheheavierdustparticlesalongthefloorwhilecreatingacloudoflighterparticleswhichincludesthemajorityofsporesVacuumingloosensandremovesallfractionsofdustandiffittedwithafinefilterwillremovemostharmfulsporesfromthestoreVacuumingisthereforemuchpreferredtosweeping
disinfectionRemovingdustandsquashedtuberswillremovethemajorityofinoculumpresentSomedustandsporeswillremainonthefloorwallsandraftersaswellasthefloorandsidesofpotatoboxesthemajorityofwhichcanberemovedbypowerwashingIftotalremovalofviablesporesisrequiredegforhighhealthcropsadisinfectantcanbeusedThisisparticularlyrelevantinstoreswheredamagerelateddiseasessuchasdryrothaveoccurred
5 Storehygiene
AcleanstorefreefromdiscardedtubersdustanddebrishasanumberofadvantagesItwillminimisecropinfectionimproveairflowcontributetoworkerhealthandcomfortandislikelytoimpressclientsandcustomers
SomesoilisinevitablybroughtintostorewiththeharvestedcropOncedrythisbecomesapotentialsourceofdustwhenthecropismovedIfthecropisfreeofdiseasewhenharvestedanditremainssooverthestorageperiodthenthedustwillbemainlymineralinnatureHoweverifthecropisdiseasedorbecomessoduringstoragethedustmaycontainlargequantitiesofsporeswhichwillbeasourceofinoculuminthepresentorfutureyears
dustdispersalConvectioncurrentscausedbyrespirationheatfromthecropwillcirculatedustandsporesthroughoutthestore
Figure 51 Vacuuming of potato store
17S T O R E m a n a g E R S rsquo g U I D E
StorEHYGIEnE
Post-storagecleaning
bullStore-cleaningshouldbeundertakenannuallyInboxstoresthisisbestcarriedoutimmediatelyafterthelastcrophasbeenremovedsocleanedboxescanbereturnedtostore
bullInayearfollowingcropinfectionbysilverscurforskinspotextrarigorouscleaningshouldbecarriedout
bullVacuumdirtanddebrisfromfloorsledgesbeamsandotherhorizontalsurfaces
bullWhereinsulationisdamagedorisroughandcollectsdustrepairandvacuum
bullOnlypowerhoseifinsulationismoisture-proof
Cleaningboxes
bullEnsurethatbox-tippersongradinglinesaredesignedtodischargethetotalboxcontentstogetridofmajorcontamination
bullUsepowerhosetocleanboxes
bullWherecleaningboxesisroutineconsidersettingupaconveyor-basedautomaticwashingsystem
bullPower-washboxesforhighhealthcrops
bullWherepossiblereturncleanedboxestostoreorkeepundercoverasthiscanextendboxlifeby70
Whentousedisinfectants
Forhighhealthseedcropsdisinfectantsmaybebeneficialespeciallyafteracontaminatedcropinthepreviousyear
bullUsedisinfectantmistfogorsprayaftervacuumingstore
bullSpraydisinfectboxeswhichhelddiseasedcropout-gradesorlsquobrockrsquo
bullFollowinggradingofdiseasedpotatoespower-washgradinglinethenspraywithdisinfectantwheregradinghighhealthcrops
bullAlwaysuseapprovedproductsandseekspecialistadvice
notesomedisinfectantsmaydamagestoreinsulationandelectricalfittingsndashconsulttheproductlabelbeforeuse
dailycleaning
bullVacuumthefloorparticularlyforkliftroutesandundergradersatleastonceaday
Gradinginstore
GradinginstoreislikelytoincreasetheamountofcontaminateddustinthestoreandthelikelihoodofambientairenteringthroughopendoorsDustprovidesdiseaseinoculumwhileambientairmaycausecondensationparticularlyonthetopsurfaceofboxesorpile
bullIdeallygradeinseparatebuildingwithaplasticstripdoorbetweenthestoreandgradingarea
bullIfgradinginstoreisunavoidableenclosepickersinwarmedcabinandfitadustcontrolsystemtotheline
bullFitdewpointtemperaturemonitortowarnofcondensationrisks
ACTION POINTS
LeavingboxesoutsidewillallowlighttokillviablesporesBoxesshouldnotbestackedmorethanfourboxeshighforsafetyandifstackedinpairsasmallgapbetweenrowswillallownatural(ultraviolet)lighttoreachonesideofeveryboxHoweveroutsidestackingcanreduceboxlifebyupto40
CleaningandenergyefficiencyMaintainingfansventilationandrefrigerationequipmentinacleanconditionwillhelpprolongtheirworkinglifeand
improvetheirworkingefficiencyEnsurethattemperatureandhumidityprobesarekeptcleanandinspectlouvresevaporatorsandcondensersIfnecessarycleanbyvacuumingorpowerwashingIfwashingtakecarearoundelectricalandmovingsystemsandensurethatanyresultingiceisremovedbydefrosting
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
9S T O R E m a n a g E R S rsquo g U I D E
StorEFEAturE
PoorPrACtICE
1 2 3BEStPrACtICE
4rEFErtoSECtIon
MonItorInGAndtrACEABILtY
temperaturesensors
Bulkstacksensorplacement
Condensationcontrol
Stockcontrol
Storerecording
LACKoFControL
Nosensorsinstore
Asabove
Asabove
Chemicalrecordsonlylegalminimum
Asabove
Inaironlycropconditionunknown
Topsurfaceonly-pronetoinfluencebyairabove
Controloftemperaturedifferentials
Chemicaluseplusstocklocationinstorerecorded
Occasionalmanualrecordingofstoretemperatures
1or2sensorsincropnomeasureoftemperaturevariation
Topandbaseofstacktomeasurepiletemperaturegradient
Relativehumiditymeasurementfordew-pointcontrol
Chemicalusestockdetailslabelledoneachbox
Regularmanualrecordingofstoretemperaturesandfanrunningtimes
FuLLCAPABILItY
1sensorper100tonnes
Ascolumn3butalso300mmdowntoanticipatecondensation
Skinresistancesensingtomeasureanywetting
Boxrecordsincludelocation-feedbackonstorageproblems
Automaticloggingofstoretemperaturesandfanrunningtimes
LoadingthestoreampStoremonitoringandqualityassurance
QCSAMPLInG Singlepointsampling Multi-pointsampling
ononelevelMulti-pointsamplingonmorethanonelevel
Comprehensivesamplingthroughoutthestore
Storageformarkets
SEEdGrAdInG
CondEnSAtIonrISK
Instore Nextdoorbutnoairlock
Nextdoorwithstripcurtain
StorEISoLAtEd
Nextdoorwithhighspeeddoor
Condensationonthecrop
10 S T O R E m a n a g E R S rsquo g U I D E
Fabricordoorleakagetowind-inducedventilationreducesthebenefitsofthestoreasitislikelytoleadtolossofenvironmentalcontrolcropweightlossandpossiblecondensationonthecropVentilationorrefrigerationrun-timewillincreasetocoolthecropwarmedbytheleakingair
ContainmentThecapitalcostofabulkstorewithload-bearinginsulatedretainingwallsishigherthanforaboxstoreButwhenthecapitalcostofboxesisaddedbulkstorageischeaperoverallBoxstoreseaseseparationfordifferentstocksandprovidemoreflexibilityforcropmovementandmarketingDeepbulkpilescanleadtopressurebruisingproblemsifthecropisstoredover40mhighorifexcessivelyventilatedbynon-humidifiedairBoxstorageisnormallyfreefrompressurebruisinganddependingontheirqualityboxescanbestackedupto8high
InsulationThequalityoftheinsulationwilldeterminetoalargeextenthowwellapotatostoreperformsInsulationisakeyfactorforapotatostoremuchmoresothanitisforgeneralpurposebuildings
MaintainingtemperaturesabovefreezingpointisseldomaproblemgiventhequantityofheatproducedinalargestoreHoweveranyheatthatleaksintoastorehastoberemovedbyexpendingenergyeitherintheformofventilationorrefrigerationInadditiontotheimplicationsoncosttheavoidableoperationofenvironmentalcontrol
2 Storagebuildings
Awellsealedandinsulatedpotatostore(Figure21)will
bullAllowthecroptobekeptatastabletemperaturelargelyunaffectedbydiurnalvariationandambientconditions
bullHelpmaintainarelativehumidityof90-100tominimisetuberweightloss
bullAllowcropstobestoredfreefromcondensationinchangeableweatherconditions
ControlledventilationControlledventilationallowscroprespirationheattoberemovedandthecroptobedriedandcooledFansarepositionedtocreateaflowofairthroughthecrop(positiveventilationbulkorbox)ortoformarollingmassofairthatwillflowoverthestackofboxesandthroughtheirpalletslots(spaceventilation)
Coolingcanbeachievedusingambientairandormechanicalcooling(refrigeration)Internalrecirculationofair(withoutcooling)canbeusedtoeliminatetemperaturevariationortodistributechemicalsforsproutsuppressionordiseasecontrol
AirflowshouldbeasuniformaspossiblethroughoutthestoretogiveevendryingandstablecroptemperaturesAwelldesignedstorewillhavebeenbalancedtoachieveuniformityofairflowatitstypicaloperatingconditionThismightincludefeaturessuchastaperedairductsorgraduatedlateraloutletstodeliversimilarquantitiesofairacrossthewholestore
Figure 21 A well sealed and insulated potato store
11S T O R E m a n a g E R S rsquo g U I D E
foundinpotatostoreswherecompositemetalpolyisocyanurate(PIR)sandwichpanelsareusedThesearecommonplacenowadaysfornewlybuiltstoresOthersystemsforupgradesofferatbestlittlemorethanavapourcheckThistendstolimitthechoiceofinsulationtoeithersprayorboardpolyurethaneoralternativelyexpandedextrudedpolystyreneboard
Specialistadviceshouldbesoughtforallaspectsofstoragebuildingdesign
equipmentwillalwaysincreasewaterlossfromthecropItisthereforejustasbeneficialtouseinsulationtolimitanyheatingressintothestoreasitistominimisetheeffectsofcoldweatherAlight-colouredreflectiveexternalsurfacewillreduceunwantedsolarradiationgains
NearlyallinsulationmaterialshavetheirperformancereducedsignificantlybyverysmallincreasesintheirmoisturecontentTheuseofvapourbarrierstoprotectinsulationisonlyeffectiveinthehighhumidityconditions
Storeassessment
bullUndertakeadetailedassessmentofyourstoreasdescribedinsection1
Balancedventilation
bullTheventilationsysteminastoreshouldbeinbalanceThismeansthatforoptimalperformancedesignfeaturesarerequiredndashegtaperedductsndashtooffsettheeffectsofpressuredropintheventilationsystemP8
doorsandlouvres
bullDoorsandlouvresaretheweakpointsoftheinsulationlsquoenvelopersquoMakesuretheycloseproperlyandstayclosedRegularpositiveactuationfromacontrollerisbeneficialforkeepingambientlouverswhicharesubjecttowindpressureclosed
Insulation
bullEnsurestoreinsulationisingoodconditionandeffective
bullWatchforsignsofcondensationwithinthestructurethatwilldegradetheinsulationvalueegdelaminatedinsulationboardswheremoisturehasgotinbehindthepanels
bullEnsureanynewbuildwithcompositeconstructionusesPIRpanelswhichareresistanttospreadofflameinthecoreintheeventoffire
ACTION POINTS
StorAGEBuILdInGS
Figure 22 Building envelope stabilises internal climate
12 S T O R E m a n a g E R S rsquo g U I D E
AllotherthingsbeingequalmoisturelossisafunctionofstorehumidityandairflowratePotatostoreswillusuallysettletoapproximately98relativehumidityandintheabsenceofahumidificationsystemthiswillbederivedbyevaporationofmoisturefromtubersInappropriatelyspecifiedrefrigerationunitscanexacerbatemoistureloss
dormancyFreshlyharvestedtubersusuallydonotsproutevenwhenconditionsareoptimalforsproutgrowthTheperiodoverwhichsproutgrowthisinhibitedbytuberphysiologyratherthanenvironmentalreasonsistermedthedormantperiodorsimplylsquodormancyrsquo
LargedifferencesindormancyoccurbetweenvarietiesWarmstoragetemperatureshaveadormancy-breakingeffectSelectionofvarietiesbydormancycharacteristicscanbeusefulforminimisingsprout-suppressantinputs
Dormancybreakistakenasthepointwhere50oftubershavesproutsof3mmormoreinlengthWarmdrysummerstendtoreducedormancy(inextremecasesleadingtosproutgrowthinthefieldbeforeharvest)whilecoolgrowingconditionswillgenerallyprolongitWaterlogginghasadormancy-breakingeffect
Woundhealing(curing)Wheretubershavebeensubjectedtowounding(egbyhandlingduringharvest)thetuberwillattempttohealthewoundndashaprocessinvolvingsuberisationandcell-divisionThespeedofthisprocesswhichisimportantforpreventingmoisturelossanddiseaseingressisaffectedbyanumberoffactorsTheseincludestoragetemperatureandhumiditywithwarmertemperaturesandhigherhumidityreducingthetimerequiredforwound-healing
Althougheffectivewound-healingisimportantconditionsthatareoptimalforcuringmayalsobesuitablefordiseasedevelopmentWherecropsareharvestedearlyundergoodconditionsorwherethestoragedurationislimitedsufficientcuringmayoccurduringtheperiodoverwhichcroptemperatureisreducedtotheholdingvalueP11
3 Cropphysiology
respirationPotatotubersarelivingorganismsandinstorecontinuetorespireandrespondtotheirenvironmentTheydosobyusingsugarsfromstarchinrespirationThisprocessconsumesoxygenandreleasescarbondioxideandsomeheatenergywhichimpactonstoragesystems
Respirationishighestatharvestandfallsrapidlytoabasallevelinthefirstweeksofstorage(Figure31)Respirationisgreaterinearly-liftedimmaturecropsthaninlate-liftedmaturecrops
Basalrespirationratedependspredominantlyonstoragetemperature(Figure32)Minimumrespirationrateisachievedataround5oCwiththerateincreasingaboveorbelowthistemperature
Handlingmechanicaldamageexposuretoethyleneandsproutingwillleadtoanincreaseinrespirationrate
EvaporationAlthoughsomemoistureislostintheprocessofrespirationmostislostbysimpleevaporationfromthetubersurfaceEffectivewound-healingandsproutcontrolisimportantinlimitingmoisturelossfromtubers
Figure 31 Respiration after lifting ndash early harvest
Figure 33 Moisture exchange between tuber skin and surrounding air in balance at ~98 relative humidity
Figure 32 Respiration in relation to storage temperature
1 2 3 4 5 6 7 8 9 10
Hea
t out
put (
Wto
nne)
35
0
5
10
15
20
25
30
Harvest date 9 September
Days after harvest
Harvest date 20 October
5 15 25
Rat
e of
resp
iratio
n (m
g C
O2k
ghr
)
12
0
2
4
6
8
10
Storage temperature (˚C)
13S T O R E m a n a g E R S rsquo g U I D E
ThisisaccomplishedsimplybyincreasingstoragetemperatureHoweverreconditioningleadstovariabilityinfrycolourandisthereforenotrecommendedasaroutinestoragepractice
PreconditioningmayalsobeusedtomaintainprocessingqualityHeretherearenodistinctcuringpull-downholdingperiodsandfrycolourorsugarcontentisusedtodeterminecropstoragetemperatureTemperaturereductiontoatargetholdingvalueonlyoccursprovidinggoodprocessingqualityismaintained
GreeningandglycoalkaloidsTubersexposedtolightwillturngreenwhichresultsfromthesynthesisofchlorophyllChlorophyllisitselfharmlessbutgreentubersaregenerallyrejectedbecausetheyhaveelevatedlevelsofglycoalkaloidsagroupofnaturaltoxicantspresentinpotatoes
TopreventgreeninginstorageexposuretolightshouldthereforebeminimisedalthoughtheneedtoseethecropclearlyandhealthandsafetyrequirementsP21willoverridethisduringloadingandsubsequentshortperiodswhenstoresareaccessedtobeinspectedorsampled
SugarsandconditioningPotatoescontainthreemainsugarsglucoseandfructose(monosaccharides)andsucrose(adisaccharide)AllthreesugarsaresweetandareimportantflavourcomponentsinwarepotatoesInpotatoesforprocessingthestoremanagerisprimarilyinterestedinthemonosaccharidesDuringprocessingthesereactwithothercomponentstoproducethebrowningwhichisassessedbymarketsasfrycolourAstoremanagersupplyingcropforprocessingmayalsobeinterestedinsucrosecontentAlthoughsucrosedoesnottakepartinbrowningreactionstrendsinsucroselevelsmaybeusedtohelpensurelowreducingsugarsandlightfrycolourduringstorage
VarietygrowthstageandstoragetemperatureareimportantindeterminingtubersugarcontentPotatoesexhibitlowtemperature-sweeteningwheresugarsaccumulatewithinthetuberastemperatureisreducedDuringstorageforprocessingtemperatureshouldthereforebemaintainedatthelowestlevelthatsafelymaintainsacceptablefrycolour
Forprocessingcropschangesinsugarcontent(andhencefrycolour)canbeachievedusingreconditioning
respiration
Thegreatertherespirationrateofthepotatoesthemorelikelyitisthatwarmairwillcondenseoncoolersurfacepotatoes
bullPositivelyventilatepotatoestoremoverespirationheattopreventsurfacecondensation
bullUsehighventilationratestopreventcondensationinheavilyrespiringearly-liftedorimmaturecropsP11
Evaporation
Moisturelossfrompotatoesduetoevaporationwilloccuriftherelativehumidity(RH)oftheairsurroundingthepotatoesislessthan98
bullKeepstorewell-sealedtominimiseweightloss
bullPreventuncontrolledexternalairingressasthisusuallyhasalowerRHthanthestorageenvironment
Sugars
Sugarsincreaseandfrycolourswilldarkenifpotatoesarestoredatcoldtemperatures
bullStorecropsforprocessingatc7-10degC
bullMonitorcold-storedpre-packpotatoesforeffectsofsugarincreaseontaste
bullIfunsurecheckstoragerequirementswithyourcustomer
ACTION POINTS
CroPPHYSIoLoGY
14 S T O R E m a n a g E R S rsquo g U I D E
Silverscurf Blackdot Skinspot dryrot Gangrene Softrot
moderateinfection
severeinfection
4 Controlofstoragediseases
DiseasecontrolisafundamentalcomponentofstoragemanagementMostdiseasesdonotoriginateinstoretheycomefromtwoprimarysourcestheseedorthesoilHowevermanyofthediseaseproblemsaffectingthepremiummarketscandeveloptosomedegreeinstoreandifnotcontrolledtheconsequencescanbecatastrophiceitherintermsofphysicalbreakdownofthecroporinlossofmarketvalueWhetherdiseasewilldevelopinstoreornot(Figure41)dependson
bullTheamountofinoculumusuallysporesorbacteriapresentonthetubersbullWhethermoisturenutrientsandtemperaturearesuitableforthediseasetogrowbullThenaturalresistanceofthetubertothediseaseorganism
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
15S T O R E m a n a g E R S rsquo g U I D E
Storemanagementallowsustoinfluencethisrelationshipparticularlyinrelationtothemicro-climatearoundthetubertocontroldiseasesduringstorage
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
Micro-climate Tuberresistance
Inoculum
Figure 41 Interaction between micro-climate and disease
notifiablediseases
SomediseasesarenotindigenousinBritainandtheirestablishmentwouldaffectthelong-termviabilityofthepotatoindustryIfsymptomsofeitherbrownrotorringrotaresuspectedthenimmediatecontactwithlocalDEFRAofficesorPlantHealthandSeedinspectorateisnecessaryVisitwwwdefragovukplanthphhtmemailplanthealthinfodefragsigovukortelephone01904455174toreportsuspectedcasesinEnglandandWalesInScotlandvisitwwwsasagovukplant_health
PreventativemeasuresexistGotowwwpotatoorguksafehaventolearnmoreaboutnationalschemesthatprotectseedandwarecrophealth
ringrotBrownrot
16 S T O R E m a n a g E R S rsquo g U I D E
Figure 52 Ensure dust and debris are removed from ducts
CrosscontaminationofsporesbetweenpotatostocksisinevitableFanventilationwithinthestoremayincreasethespeedofthismovementcomparedwithnaturalconvectionButtheairflowisabenefitasithelpskeepthecropfreefromcondensationpreventinganysporeswhichdosettlefromgerminating
MajordustmovementanddispersaloccurswhenforklifttrucksstirupdustonthefloorduringhandlingTheresultantdustcloudwillsettleontopofthecropwherethecondensationneededforgerminationismostlikelyIfgradingiscarriedoutwithinthestorethiswillalsocreateaconsiderabledustcloudwithsimilarconsequences
dustremovalSweepingwithabrushmovestheheavierdustparticlesalongthefloorwhilecreatingacloudoflighterparticleswhichincludesthemajorityofsporesVacuumingloosensandremovesallfractionsofdustandiffittedwithafinefilterwillremovemostharmfulsporesfromthestoreVacuumingisthereforemuchpreferredtosweeping
disinfectionRemovingdustandsquashedtuberswillremovethemajorityofinoculumpresentSomedustandsporeswillremainonthefloorwallsandraftersaswellasthefloorandsidesofpotatoboxesthemajorityofwhichcanberemovedbypowerwashingIftotalremovalofviablesporesisrequiredegforhighhealthcropsadisinfectantcanbeusedThisisparticularlyrelevantinstoreswheredamagerelateddiseasessuchasdryrothaveoccurred
5 Storehygiene
AcleanstorefreefromdiscardedtubersdustanddebrishasanumberofadvantagesItwillminimisecropinfectionimproveairflowcontributetoworkerhealthandcomfortandislikelytoimpressclientsandcustomers
SomesoilisinevitablybroughtintostorewiththeharvestedcropOncedrythisbecomesapotentialsourceofdustwhenthecropismovedIfthecropisfreeofdiseasewhenharvestedanditremainssooverthestorageperiodthenthedustwillbemainlymineralinnatureHoweverifthecropisdiseasedorbecomessoduringstoragethedustmaycontainlargequantitiesofsporeswhichwillbeasourceofinoculuminthepresentorfutureyears
dustdispersalConvectioncurrentscausedbyrespirationheatfromthecropwillcirculatedustandsporesthroughoutthestore
Figure 51 Vacuuming of potato store
17S T O R E m a n a g E R S rsquo g U I D E
StorEHYGIEnE
Post-storagecleaning
bullStore-cleaningshouldbeundertakenannuallyInboxstoresthisisbestcarriedoutimmediatelyafterthelastcrophasbeenremovedsocleanedboxescanbereturnedtostore
bullInayearfollowingcropinfectionbysilverscurforskinspotextrarigorouscleaningshouldbecarriedout
bullVacuumdirtanddebrisfromfloorsledgesbeamsandotherhorizontalsurfaces
bullWhereinsulationisdamagedorisroughandcollectsdustrepairandvacuum
bullOnlypowerhoseifinsulationismoisture-proof
Cleaningboxes
bullEnsurethatbox-tippersongradinglinesaredesignedtodischargethetotalboxcontentstogetridofmajorcontamination
bullUsepowerhosetocleanboxes
bullWherecleaningboxesisroutineconsidersettingupaconveyor-basedautomaticwashingsystem
bullPower-washboxesforhighhealthcrops
bullWherepossiblereturncleanedboxestostoreorkeepundercoverasthiscanextendboxlifeby70
Whentousedisinfectants
Forhighhealthseedcropsdisinfectantsmaybebeneficialespeciallyafteracontaminatedcropinthepreviousyear
bullUsedisinfectantmistfogorsprayaftervacuumingstore
bullSpraydisinfectboxeswhichhelddiseasedcropout-gradesorlsquobrockrsquo
bullFollowinggradingofdiseasedpotatoespower-washgradinglinethenspraywithdisinfectantwheregradinghighhealthcrops
bullAlwaysuseapprovedproductsandseekspecialistadvice
notesomedisinfectantsmaydamagestoreinsulationandelectricalfittingsndashconsulttheproductlabelbeforeuse
dailycleaning
bullVacuumthefloorparticularlyforkliftroutesandundergradersatleastonceaday
Gradinginstore
GradinginstoreislikelytoincreasetheamountofcontaminateddustinthestoreandthelikelihoodofambientairenteringthroughopendoorsDustprovidesdiseaseinoculumwhileambientairmaycausecondensationparticularlyonthetopsurfaceofboxesorpile
bullIdeallygradeinseparatebuildingwithaplasticstripdoorbetweenthestoreandgradingarea
bullIfgradinginstoreisunavoidableenclosepickersinwarmedcabinandfitadustcontrolsystemtotheline
bullFitdewpointtemperaturemonitortowarnofcondensationrisks
ACTION POINTS
LeavingboxesoutsidewillallowlighttokillviablesporesBoxesshouldnotbestackedmorethanfourboxeshighforsafetyandifstackedinpairsasmallgapbetweenrowswillallownatural(ultraviolet)lighttoreachonesideofeveryboxHoweveroutsidestackingcanreduceboxlifebyupto40
CleaningandenergyefficiencyMaintainingfansventilationandrefrigerationequipmentinacleanconditionwillhelpprolongtheirworkinglifeand
improvetheirworkingefficiencyEnsurethattemperatureandhumidityprobesarekeptcleanandinspectlouvresevaporatorsandcondensersIfnecessarycleanbyvacuumingorpowerwashingIfwashingtakecarearoundelectricalandmovingsystemsandensurethatanyresultingiceisremovedbydefrosting
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
10 S T O R E m a n a g E R S rsquo g U I D E
Fabricordoorleakagetowind-inducedventilationreducesthebenefitsofthestoreasitislikelytoleadtolossofenvironmentalcontrolcropweightlossandpossiblecondensationonthecropVentilationorrefrigerationrun-timewillincreasetocoolthecropwarmedbytheleakingair
ContainmentThecapitalcostofabulkstorewithload-bearinginsulatedretainingwallsishigherthanforaboxstoreButwhenthecapitalcostofboxesisaddedbulkstorageischeaperoverallBoxstoreseaseseparationfordifferentstocksandprovidemoreflexibilityforcropmovementandmarketingDeepbulkpilescanleadtopressurebruisingproblemsifthecropisstoredover40mhighorifexcessivelyventilatedbynon-humidifiedairBoxstorageisnormallyfreefrompressurebruisinganddependingontheirqualityboxescanbestackedupto8high
InsulationThequalityoftheinsulationwilldeterminetoalargeextenthowwellapotatostoreperformsInsulationisakeyfactorforapotatostoremuchmoresothanitisforgeneralpurposebuildings
MaintainingtemperaturesabovefreezingpointisseldomaproblemgiventhequantityofheatproducedinalargestoreHoweveranyheatthatleaksintoastorehastoberemovedbyexpendingenergyeitherintheformofventilationorrefrigerationInadditiontotheimplicationsoncosttheavoidableoperationofenvironmentalcontrol
2 Storagebuildings
Awellsealedandinsulatedpotatostore(Figure21)will
bullAllowthecroptobekeptatastabletemperaturelargelyunaffectedbydiurnalvariationandambientconditions
bullHelpmaintainarelativehumidityof90-100tominimisetuberweightloss
bullAllowcropstobestoredfreefromcondensationinchangeableweatherconditions
ControlledventilationControlledventilationallowscroprespirationheattoberemovedandthecroptobedriedandcooledFansarepositionedtocreateaflowofairthroughthecrop(positiveventilationbulkorbox)ortoformarollingmassofairthatwillflowoverthestackofboxesandthroughtheirpalletslots(spaceventilation)
Coolingcanbeachievedusingambientairandormechanicalcooling(refrigeration)Internalrecirculationofair(withoutcooling)canbeusedtoeliminatetemperaturevariationortodistributechemicalsforsproutsuppressionordiseasecontrol
AirflowshouldbeasuniformaspossiblethroughoutthestoretogiveevendryingandstablecroptemperaturesAwelldesignedstorewillhavebeenbalancedtoachieveuniformityofairflowatitstypicaloperatingconditionThismightincludefeaturessuchastaperedairductsorgraduatedlateraloutletstodeliversimilarquantitiesofairacrossthewholestore
Figure 21 A well sealed and insulated potato store
11S T O R E m a n a g E R S rsquo g U I D E
foundinpotatostoreswherecompositemetalpolyisocyanurate(PIR)sandwichpanelsareusedThesearecommonplacenowadaysfornewlybuiltstoresOthersystemsforupgradesofferatbestlittlemorethanavapourcheckThistendstolimitthechoiceofinsulationtoeithersprayorboardpolyurethaneoralternativelyexpandedextrudedpolystyreneboard
Specialistadviceshouldbesoughtforallaspectsofstoragebuildingdesign
equipmentwillalwaysincreasewaterlossfromthecropItisthereforejustasbeneficialtouseinsulationtolimitanyheatingressintothestoreasitistominimisetheeffectsofcoldweatherAlight-colouredreflectiveexternalsurfacewillreduceunwantedsolarradiationgains
NearlyallinsulationmaterialshavetheirperformancereducedsignificantlybyverysmallincreasesintheirmoisturecontentTheuseofvapourbarrierstoprotectinsulationisonlyeffectiveinthehighhumidityconditions
Storeassessment
bullUndertakeadetailedassessmentofyourstoreasdescribedinsection1
Balancedventilation
bullTheventilationsysteminastoreshouldbeinbalanceThismeansthatforoptimalperformancedesignfeaturesarerequiredndashegtaperedductsndashtooffsettheeffectsofpressuredropintheventilationsystemP8
doorsandlouvres
bullDoorsandlouvresaretheweakpointsoftheinsulationlsquoenvelopersquoMakesuretheycloseproperlyandstayclosedRegularpositiveactuationfromacontrollerisbeneficialforkeepingambientlouverswhicharesubjecttowindpressureclosed
Insulation
bullEnsurestoreinsulationisingoodconditionandeffective
bullWatchforsignsofcondensationwithinthestructurethatwilldegradetheinsulationvalueegdelaminatedinsulationboardswheremoisturehasgotinbehindthepanels
bullEnsureanynewbuildwithcompositeconstructionusesPIRpanelswhichareresistanttospreadofflameinthecoreintheeventoffire
ACTION POINTS
StorAGEBuILdInGS
Figure 22 Building envelope stabilises internal climate
12 S T O R E m a n a g E R S rsquo g U I D E
AllotherthingsbeingequalmoisturelossisafunctionofstorehumidityandairflowratePotatostoreswillusuallysettletoapproximately98relativehumidityandintheabsenceofahumidificationsystemthiswillbederivedbyevaporationofmoisturefromtubersInappropriatelyspecifiedrefrigerationunitscanexacerbatemoistureloss
dormancyFreshlyharvestedtubersusuallydonotsproutevenwhenconditionsareoptimalforsproutgrowthTheperiodoverwhichsproutgrowthisinhibitedbytuberphysiologyratherthanenvironmentalreasonsistermedthedormantperiodorsimplylsquodormancyrsquo
LargedifferencesindormancyoccurbetweenvarietiesWarmstoragetemperatureshaveadormancy-breakingeffectSelectionofvarietiesbydormancycharacteristicscanbeusefulforminimisingsprout-suppressantinputs
Dormancybreakistakenasthepointwhere50oftubershavesproutsof3mmormoreinlengthWarmdrysummerstendtoreducedormancy(inextremecasesleadingtosproutgrowthinthefieldbeforeharvest)whilecoolgrowingconditionswillgenerallyprolongitWaterlogginghasadormancy-breakingeffect
Woundhealing(curing)Wheretubershavebeensubjectedtowounding(egbyhandlingduringharvest)thetuberwillattempttohealthewoundndashaprocessinvolvingsuberisationandcell-divisionThespeedofthisprocesswhichisimportantforpreventingmoisturelossanddiseaseingressisaffectedbyanumberoffactorsTheseincludestoragetemperatureandhumiditywithwarmertemperaturesandhigherhumidityreducingthetimerequiredforwound-healing
Althougheffectivewound-healingisimportantconditionsthatareoptimalforcuringmayalsobesuitablefordiseasedevelopmentWherecropsareharvestedearlyundergoodconditionsorwherethestoragedurationislimitedsufficientcuringmayoccurduringtheperiodoverwhichcroptemperatureisreducedtotheholdingvalueP11
3 Cropphysiology
respirationPotatotubersarelivingorganismsandinstorecontinuetorespireandrespondtotheirenvironmentTheydosobyusingsugarsfromstarchinrespirationThisprocessconsumesoxygenandreleasescarbondioxideandsomeheatenergywhichimpactonstoragesystems
Respirationishighestatharvestandfallsrapidlytoabasallevelinthefirstweeksofstorage(Figure31)Respirationisgreaterinearly-liftedimmaturecropsthaninlate-liftedmaturecrops
Basalrespirationratedependspredominantlyonstoragetemperature(Figure32)Minimumrespirationrateisachievedataround5oCwiththerateincreasingaboveorbelowthistemperature
Handlingmechanicaldamageexposuretoethyleneandsproutingwillleadtoanincreaseinrespirationrate
EvaporationAlthoughsomemoistureislostintheprocessofrespirationmostislostbysimpleevaporationfromthetubersurfaceEffectivewound-healingandsproutcontrolisimportantinlimitingmoisturelossfromtubers
Figure 31 Respiration after lifting ndash early harvest
Figure 33 Moisture exchange between tuber skin and surrounding air in balance at ~98 relative humidity
Figure 32 Respiration in relation to storage temperature
1 2 3 4 5 6 7 8 9 10
Hea
t out
put (
Wto
nne)
35
0
5
10
15
20
25
30
Harvest date 9 September
Days after harvest
Harvest date 20 October
5 15 25
Rat
e of
resp
iratio
n (m
g C
O2k
ghr
)
12
0
2
4
6
8
10
Storage temperature (˚C)
13S T O R E m a n a g E R S rsquo g U I D E
ThisisaccomplishedsimplybyincreasingstoragetemperatureHoweverreconditioningleadstovariabilityinfrycolourandisthereforenotrecommendedasaroutinestoragepractice
PreconditioningmayalsobeusedtomaintainprocessingqualityHeretherearenodistinctcuringpull-downholdingperiodsandfrycolourorsugarcontentisusedtodeterminecropstoragetemperatureTemperaturereductiontoatargetholdingvalueonlyoccursprovidinggoodprocessingqualityismaintained
GreeningandglycoalkaloidsTubersexposedtolightwillturngreenwhichresultsfromthesynthesisofchlorophyllChlorophyllisitselfharmlessbutgreentubersaregenerallyrejectedbecausetheyhaveelevatedlevelsofglycoalkaloidsagroupofnaturaltoxicantspresentinpotatoes
TopreventgreeninginstorageexposuretolightshouldthereforebeminimisedalthoughtheneedtoseethecropclearlyandhealthandsafetyrequirementsP21willoverridethisduringloadingandsubsequentshortperiodswhenstoresareaccessedtobeinspectedorsampled
SugarsandconditioningPotatoescontainthreemainsugarsglucoseandfructose(monosaccharides)andsucrose(adisaccharide)AllthreesugarsaresweetandareimportantflavourcomponentsinwarepotatoesInpotatoesforprocessingthestoremanagerisprimarilyinterestedinthemonosaccharidesDuringprocessingthesereactwithothercomponentstoproducethebrowningwhichisassessedbymarketsasfrycolourAstoremanagersupplyingcropforprocessingmayalsobeinterestedinsucrosecontentAlthoughsucrosedoesnottakepartinbrowningreactionstrendsinsucroselevelsmaybeusedtohelpensurelowreducingsugarsandlightfrycolourduringstorage
VarietygrowthstageandstoragetemperatureareimportantindeterminingtubersugarcontentPotatoesexhibitlowtemperature-sweeteningwheresugarsaccumulatewithinthetuberastemperatureisreducedDuringstorageforprocessingtemperatureshouldthereforebemaintainedatthelowestlevelthatsafelymaintainsacceptablefrycolour
Forprocessingcropschangesinsugarcontent(andhencefrycolour)canbeachievedusingreconditioning
respiration
Thegreatertherespirationrateofthepotatoesthemorelikelyitisthatwarmairwillcondenseoncoolersurfacepotatoes
bullPositivelyventilatepotatoestoremoverespirationheattopreventsurfacecondensation
bullUsehighventilationratestopreventcondensationinheavilyrespiringearly-liftedorimmaturecropsP11
Evaporation
Moisturelossfrompotatoesduetoevaporationwilloccuriftherelativehumidity(RH)oftheairsurroundingthepotatoesislessthan98
bullKeepstorewell-sealedtominimiseweightloss
bullPreventuncontrolledexternalairingressasthisusuallyhasalowerRHthanthestorageenvironment
Sugars
Sugarsincreaseandfrycolourswilldarkenifpotatoesarestoredatcoldtemperatures
bullStorecropsforprocessingatc7-10degC
bullMonitorcold-storedpre-packpotatoesforeffectsofsugarincreaseontaste
bullIfunsurecheckstoragerequirementswithyourcustomer
ACTION POINTS
CroPPHYSIoLoGY
14 S T O R E m a n a g E R S rsquo g U I D E
Silverscurf Blackdot Skinspot dryrot Gangrene Softrot
moderateinfection
severeinfection
4 Controlofstoragediseases
DiseasecontrolisafundamentalcomponentofstoragemanagementMostdiseasesdonotoriginateinstoretheycomefromtwoprimarysourcestheseedorthesoilHowevermanyofthediseaseproblemsaffectingthepremiummarketscandeveloptosomedegreeinstoreandifnotcontrolledtheconsequencescanbecatastrophiceitherintermsofphysicalbreakdownofthecroporinlossofmarketvalueWhetherdiseasewilldevelopinstoreornot(Figure41)dependson
bullTheamountofinoculumusuallysporesorbacteriapresentonthetubersbullWhethermoisturenutrientsandtemperaturearesuitableforthediseasetogrowbullThenaturalresistanceofthetubertothediseaseorganism
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
15S T O R E m a n a g E R S rsquo g U I D E
Storemanagementallowsustoinfluencethisrelationshipparticularlyinrelationtothemicro-climatearoundthetubertocontroldiseasesduringstorage
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
Micro-climate Tuberresistance
Inoculum
Figure 41 Interaction between micro-climate and disease
notifiablediseases
SomediseasesarenotindigenousinBritainandtheirestablishmentwouldaffectthelong-termviabilityofthepotatoindustryIfsymptomsofeitherbrownrotorringrotaresuspectedthenimmediatecontactwithlocalDEFRAofficesorPlantHealthandSeedinspectorateisnecessaryVisitwwwdefragovukplanthphhtmemailplanthealthinfodefragsigovukortelephone01904455174toreportsuspectedcasesinEnglandandWalesInScotlandvisitwwwsasagovukplant_health
PreventativemeasuresexistGotowwwpotatoorguksafehaventolearnmoreaboutnationalschemesthatprotectseedandwarecrophealth
ringrotBrownrot
16 S T O R E m a n a g E R S rsquo g U I D E
Figure 52 Ensure dust and debris are removed from ducts
CrosscontaminationofsporesbetweenpotatostocksisinevitableFanventilationwithinthestoremayincreasethespeedofthismovementcomparedwithnaturalconvectionButtheairflowisabenefitasithelpskeepthecropfreefromcondensationpreventinganysporeswhichdosettlefromgerminating
MajordustmovementanddispersaloccurswhenforklifttrucksstirupdustonthefloorduringhandlingTheresultantdustcloudwillsettleontopofthecropwherethecondensationneededforgerminationismostlikelyIfgradingiscarriedoutwithinthestorethiswillalsocreateaconsiderabledustcloudwithsimilarconsequences
dustremovalSweepingwithabrushmovestheheavierdustparticlesalongthefloorwhilecreatingacloudoflighterparticleswhichincludesthemajorityofsporesVacuumingloosensandremovesallfractionsofdustandiffittedwithafinefilterwillremovemostharmfulsporesfromthestoreVacuumingisthereforemuchpreferredtosweeping
disinfectionRemovingdustandsquashedtuberswillremovethemajorityofinoculumpresentSomedustandsporeswillremainonthefloorwallsandraftersaswellasthefloorandsidesofpotatoboxesthemajorityofwhichcanberemovedbypowerwashingIftotalremovalofviablesporesisrequiredegforhighhealthcropsadisinfectantcanbeusedThisisparticularlyrelevantinstoreswheredamagerelateddiseasessuchasdryrothaveoccurred
5 Storehygiene
AcleanstorefreefromdiscardedtubersdustanddebrishasanumberofadvantagesItwillminimisecropinfectionimproveairflowcontributetoworkerhealthandcomfortandislikelytoimpressclientsandcustomers
SomesoilisinevitablybroughtintostorewiththeharvestedcropOncedrythisbecomesapotentialsourceofdustwhenthecropismovedIfthecropisfreeofdiseasewhenharvestedanditremainssooverthestorageperiodthenthedustwillbemainlymineralinnatureHoweverifthecropisdiseasedorbecomessoduringstoragethedustmaycontainlargequantitiesofsporeswhichwillbeasourceofinoculuminthepresentorfutureyears
dustdispersalConvectioncurrentscausedbyrespirationheatfromthecropwillcirculatedustandsporesthroughoutthestore
Figure 51 Vacuuming of potato store
17S T O R E m a n a g E R S rsquo g U I D E
StorEHYGIEnE
Post-storagecleaning
bullStore-cleaningshouldbeundertakenannuallyInboxstoresthisisbestcarriedoutimmediatelyafterthelastcrophasbeenremovedsocleanedboxescanbereturnedtostore
bullInayearfollowingcropinfectionbysilverscurforskinspotextrarigorouscleaningshouldbecarriedout
bullVacuumdirtanddebrisfromfloorsledgesbeamsandotherhorizontalsurfaces
bullWhereinsulationisdamagedorisroughandcollectsdustrepairandvacuum
bullOnlypowerhoseifinsulationismoisture-proof
Cleaningboxes
bullEnsurethatbox-tippersongradinglinesaredesignedtodischargethetotalboxcontentstogetridofmajorcontamination
bullUsepowerhosetocleanboxes
bullWherecleaningboxesisroutineconsidersettingupaconveyor-basedautomaticwashingsystem
bullPower-washboxesforhighhealthcrops
bullWherepossiblereturncleanedboxestostoreorkeepundercoverasthiscanextendboxlifeby70
Whentousedisinfectants
Forhighhealthseedcropsdisinfectantsmaybebeneficialespeciallyafteracontaminatedcropinthepreviousyear
bullUsedisinfectantmistfogorsprayaftervacuumingstore
bullSpraydisinfectboxeswhichhelddiseasedcropout-gradesorlsquobrockrsquo
bullFollowinggradingofdiseasedpotatoespower-washgradinglinethenspraywithdisinfectantwheregradinghighhealthcrops
bullAlwaysuseapprovedproductsandseekspecialistadvice
notesomedisinfectantsmaydamagestoreinsulationandelectricalfittingsndashconsulttheproductlabelbeforeuse
dailycleaning
bullVacuumthefloorparticularlyforkliftroutesandundergradersatleastonceaday
Gradinginstore
GradinginstoreislikelytoincreasetheamountofcontaminateddustinthestoreandthelikelihoodofambientairenteringthroughopendoorsDustprovidesdiseaseinoculumwhileambientairmaycausecondensationparticularlyonthetopsurfaceofboxesorpile
bullIdeallygradeinseparatebuildingwithaplasticstripdoorbetweenthestoreandgradingarea
bullIfgradinginstoreisunavoidableenclosepickersinwarmedcabinandfitadustcontrolsystemtotheline
bullFitdewpointtemperaturemonitortowarnofcondensationrisks
ACTION POINTS
LeavingboxesoutsidewillallowlighttokillviablesporesBoxesshouldnotbestackedmorethanfourboxeshighforsafetyandifstackedinpairsasmallgapbetweenrowswillallownatural(ultraviolet)lighttoreachonesideofeveryboxHoweveroutsidestackingcanreduceboxlifebyupto40
CleaningandenergyefficiencyMaintainingfansventilationandrefrigerationequipmentinacleanconditionwillhelpprolongtheirworkinglifeand
improvetheirworkingefficiencyEnsurethattemperatureandhumidityprobesarekeptcleanandinspectlouvresevaporatorsandcondensersIfnecessarycleanbyvacuumingorpowerwashingIfwashingtakecarearoundelectricalandmovingsystemsandensurethatanyresultingiceisremovedbydefrosting
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
11S T O R E m a n a g E R S rsquo g U I D E
foundinpotatostoreswherecompositemetalpolyisocyanurate(PIR)sandwichpanelsareusedThesearecommonplacenowadaysfornewlybuiltstoresOthersystemsforupgradesofferatbestlittlemorethanavapourcheckThistendstolimitthechoiceofinsulationtoeithersprayorboardpolyurethaneoralternativelyexpandedextrudedpolystyreneboard
Specialistadviceshouldbesoughtforallaspectsofstoragebuildingdesign
equipmentwillalwaysincreasewaterlossfromthecropItisthereforejustasbeneficialtouseinsulationtolimitanyheatingressintothestoreasitistominimisetheeffectsofcoldweatherAlight-colouredreflectiveexternalsurfacewillreduceunwantedsolarradiationgains
NearlyallinsulationmaterialshavetheirperformancereducedsignificantlybyverysmallincreasesintheirmoisturecontentTheuseofvapourbarrierstoprotectinsulationisonlyeffectiveinthehighhumidityconditions
Storeassessment
bullUndertakeadetailedassessmentofyourstoreasdescribedinsection1
Balancedventilation
bullTheventilationsysteminastoreshouldbeinbalanceThismeansthatforoptimalperformancedesignfeaturesarerequiredndashegtaperedductsndashtooffsettheeffectsofpressuredropintheventilationsystemP8
doorsandlouvres
bullDoorsandlouvresaretheweakpointsoftheinsulationlsquoenvelopersquoMakesuretheycloseproperlyandstayclosedRegularpositiveactuationfromacontrollerisbeneficialforkeepingambientlouverswhicharesubjecttowindpressureclosed
Insulation
bullEnsurestoreinsulationisingoodconditionandeffective
bullWatchforsignsofcondensationwithinthestructurethatwilldegradetheinsulationvalueegdelaminatedinsulationboardswheremoisturehasgotinbehindthepanels
bullEnsureanynewbuildwithcompositeconstructionusesPIRpanelswhichareresistanttospreadofflameinthecoreintheeventoffire
ACTION POINTS
StorAGEBuILdInGS
Figure 22 Building envelope stabilises internal climate
12 S T O R E m a n a g E R S rsquo g U I D E
AllotherthingsbeingequalmoisturelossisafunctionofstorehumidityandairflowratePotatostoreswillusuallysettletoapproximately98relativehumidityandintheabsenceofahumidificationsystemthiswillbederivedbyevaporationofmoisturefromtubersInappropriatelyspecifiedrefrigerationunitscanexacerbatemoistureloss
dormancyFreshlyharvestedtubersusuallydonotsproutevenwhenconditionsareoptimalforsproutgrowthTheperiodoverwhichsproutgrowthisinhibitedbytuberphysiologyratherthanenvironmentalreasonsistermedthedormantperiodorsimplylsquodormancyrsquo
LargedifferencesindormancyoccurbetweenvarietiesWarmstoragetemperatureshaveadormancy-breakingeffectSelectionofvarietiesbydormancycharacteristicscanbeusefulforminimisingsprout-suppressantinputs
Dormancybreakistakenasthepointwhere50oftubershavesproutsof3mmormoreinlengthWarmdrysummerstendtoreducedormancy(inextremecasesleadingtosproutgrowthinthefieldbeforeharvest)whilecoolgrowingconditionswillgenerallyprolongitWaterlogginghasadormancy-breakingeffect
Woundhealing(curing)Wheretubershavebeensubjectedtowounding(egbyhandlingduringharvest)thetuberwillattempttohealthewoundndashaprocessinvolvingsuberisationandcell-divisionThespeedofthisprocesswhichisimportantforpreventingmoisturelossanddiseaseingressisaffectedbyanumberoffactorsTheseincludestoragetemperatureandhumiditywithwarmertemperaturesandhigherhumidityreducingthetimerequiredforwound-healing
Althougheffectivewound-healingisimportantconditionsthatareoptimalforcuringmayalsobesuitablefordiseasedevelopmentWherecropsareharvestedearlyundergoodconditionsorwherethestoragedurationislimitedsufficientcuringmayoccurduringtheperiodoverwhichcroptemperatureisreducedtotheholdingvalueP11
3 Cropphysiology
respirationPotatotubersarelivingorganismsandinstorecontinuetorespireandrespondtotheirenvironmentTheydosobyusingsugarsfromstarchinrespirationThisprocessconsumesoxygenandreleasescarbondioxideandsomeheatenergywhichimpactonstoragesystems
Respirationishighestatharvestandfallsrapidlytoabasallevelinthefirstweeksofstorage(Figure31)Respirationisgreaterinearly-liftedimmaturecropsthaninlate-liftedmaturecrops
Basalrespirationratedependspredominantlyonstoragetemperature(Figure32)Minimumrespirationrateisachievedataround5oCwiththerateincreasingaboveorbelowthistemperature
Handlingmechanicaldamageexposuretoethyleneandsproutingwillleadtoanincreaseinrespirationrate
EvaporationAlthoughsomemoistureislostintheprocessofrespirationmostislostbysimpleevaporationfromthetubersurfaceEffectivewound-healingandsproutcontrolisimportantinlimitingmoisturelossfromtubers
Figure 31 Respiration after lifting ndash early harvest
Figure 33 Moisture exchange between tuber skin and surrounding air in balance at ~98 relative humidity
Figure 32 Respiration in relation to storage temperature
1 2 3 4 5 6 7 8 9 10
Hea
t out
put (
Wto
nne)
35
0
5
10
15
20
25
30
Harvest date 9 September
Days after harvest
Harvest date 20 October
5 15 25
Rat
e of
resp
iratio
n (m
g C
O2k
ghr
)
12
0
2
4
6
8
10
Storage temperature (˚C)
13S T O R E m a n a g E R S rsquo g U I D E
ThisisaccomplishedsimplybyincreasingstoragetemperatureHoweverreconditioningleadstovariabilityinfrycolourandisthereforenotrecommendedasaroutinestoragepractice
PreconditioningmayalsobeusedtomaintainprocessingqualityHeretherearenodistinctcuringpull-downholdingperiodsandfrycolourorsugarcontentisusedtodeterminecropstoragetemperatureTemperaturereductiontoatargetholdingvalueonlyoccursprovidinggoodprocessingqualityismaintained
GreeningandglycoalkaloidsTubersexposedtolightwillturngreenwhichresultsfromthesynthesisofchlorophyllChlorophyllisitselfharmlessbutgreentubersaregenerallyrejectedbecausetheyhaveelevatedlevelsofglycoalkaloidsagroupofnaturaltoxicantspresentinpotatoes
TopreventgreeninginstorageexposuretolightshouldthereforebeminimisedalthoughtheneedtoseethecropclearlyandhealthandsafetyrequirementsP21willoverridethisduringloadingandsubsequentshortperiodswhenstoresareaccessedtobeinspectedorsampled
SugarsandconditioningPotatoescontainthreemainsugarsglucoseandfructose(monosaccharides)andsucrose(adisaccharide)AllthreesugarsaresweetandareimportantflavourcomponentsinwarepotatoesInpotatoesforprocessingthestoremanagerisprimarilyinterestedinthemonosaccharidesDuringprocessingthesereactwithothercomponentstoproducethebrowningwhichisassessedbymarketsasfrycolourAstoremanagersupplyingcropforprocessingmayalsobeinterestedinsucrosecontentAlthoughsucrosedoesnottakepartinbrowningreactionstrendsinsucroselevelsmaybeusedtohelpensurelowreducingsugarsandlightfrycolourduringstorage
VarietygrowthstageandstoragetemperatureareimportantindeterminingtubersugarcontentPotatoesexhibitlowtemperature-sweeteningwheresugarsaccumulatewithinthetuberastemperatureisreducedDuringstorageforprocessingtemperatureshouldthereforebemaintainedatthelowestlevelthatsafelymaintainsacceptablefrycolour
Forprocessingcropschangesinsugarcontent(andhencefrycolour)canbeachievedusingreconditioning
respiration
Thegreatertherespirationrateofthepotatoesthemorelikelyitisthatwarmairwillcondenseoncoolersurfacepotatoes
bullPositivelyventilatepotatoestoremoverespirationheattopreventsurfacecondensation
bullUsehighventilationratestopreventcondensationinheavilyrespiringearly-liftedorimmaturecropsP11
Evaporation
Moisturelossfrompotatoesduetoevaporationwilloccuriftherelativehumidity(RH)oftheairsurroundingthepotatoesislessthan98
bullKeepstorewell-sealedtominimiseweightloss
bullPreventuncontrolledexternalairingressasthisusuallyhasalowerRHthanthestorageenvironment
Sugars
Sugarsincreaseandfrycolourswilldarkenifpotatoesarestoredatcoldtemperatures
bullStorecropsforprocessingatc7-10degC
bullMonitorcold-storedpre-packpotatoesforeffectsofsugarincreaseontaste
bullIfunsurecheckstoragerequirementswithyourcustomer
ACTION POINTS
CroPPHYSIoLoGY
14 S T O R E m a n a g E R S rsquo g U I D E
Silverscurf Blackdot Skinspot dryrot Gangrene Softrot
moderateinfection
severeinfection
4 Controlofstoragediseases
DiseasecontrolisafundamentalcomponentofstoragemanagementMostdiseasesdonotoriginateinstoretheycomefromtwoprimarysourcestheseedorthesoilHowevermanyofthediseaseproblemsaffectingthepremiummarketscandeveloptosomedegreeinstoreandifnotcontrolledtheconsequencescanbecatastrophiceitherintermsofphysicalbreakdownofthecroporinlossofmarketvalueWhetherdiseasewilldevelopinstoreornot(Figure41)dependson
bullTheamountofinoculumusuallysporesorbacteriapresentonthetubersbullWhethermoisturenutrientsandtemperaturearesuitableforthediseasetogrowbullThenaturalresistanceofthetubertothediseaseorganism
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
15S T O R E m a n a g E R S rsquo g U I D E
Storemanagementallowsustoinfluencethisrelationshipparticularlyinrelationtothemicro-climatearoundthetubertocontroldiseasesduringstorage
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
Micro-climate Tuberresistance
Inoculum
Figure 41 Interaction between micro-climate and disease
notifiablediseases
SomediseasesarenotindigenousinBritainandtheirestablishmentwouldaffectthelong-termviabilityofthepotatoindustryIfsymptomsofeitherbrownrotorringrotaresuspectedthenimmediatecontactwithlocalDEFRAofficesorPlantHealthandSeedinspectorateisnecessaryVisitwwwdefragovukplanthphhtmemailplanthealthinfodefragsigovukortelephone01904455174toreportsuspectedcasesinEnglandandWalesInScotlandvisitwwwsasagovukplant_health
PreventativemeasuresexistGotowwwpotatoorguksafehaventolearnmoreaboutnationalschemesthatprotectseedandwarecrophealth
ringrotBrownrot
16 S T O R E m a n a g E R S rsquo g U I D E
Figure 52 Ensure dust and debris are removed from ducts
CrosscontaminationofsporesbetweenpotatostocksisinevitableFanventilationwithinthestoremayincreasethespeedofthismovementcomparedwithnaturalconvectionButtheairflowisabenefitasithelpskeepthecropfreefromcondensationpreventinganysporeswhichdosettlefromgerminating
MajordustmovementanddispersaloccurswhenforklifttrucksstirupdustonthefloorduringhandlingTheresultantdustcloudwillsettleontopofthecropwherethecondensationneededforgerminationismostlikelyIfgradingiscarriedoutwithinthestorethiswillalsocreateaconsiderabledustcloudwithsimilarconsequences
dustremovalSweepingwithabrushmovestheheavierdustparticlesalongthefloorwhilecreatingacloudoflighterparticleswhichincludesthemajorityofsporesVacuumingloosensandremovesallfractionsofdustandiffittedwithafinefilterwillremovemostharmfulsporesfromthestoreVacuumingisthereforemuchpreferredtosweeping
disinfectionRemovingdustandsquashedtuberswillremovethemajorityofinoculumpresentSomedustandsporeswillremainonthefloorwallsandraftersaswellasthefloorandsidesofpotatoboxesthemajorityofwhichcanberemovedbypowerwashingIftotalremovalofviablesporesisrequiredegforhighhealthcropsadisinfectantcanbeusedThisisparticularlyrelevantinstoreswheredamagerelateddiseasessuchasdryrothaveoccurred
5 Storehygiene
AcleanstorefreefromdiscardedtubersdustanddebrishasanumberofadvantagesItwillminimisecropinfectionimproveairflowcontributetoworkerhealthandcomfortandislikelytoimpressclientsandcustomers
SomesoilisinevitablybroughtintostorewiththeharvestedcropOncedrythisbecomesapotentialsourceofdustwhenthecropismovedIfthecropisfreeofdiseasewhenharvestedanditremainssooverthestorageperiodthenthedustwillbemainlymineralinnatureHoweverifthecropisdiseasedorbecomessoduringstoragethedustmaycontainlargequantitiesofsporeswhichwillbeasourceofinoculuminthepresentorfutureyears
dustdispersalConvectioncurrentscausedbyrespirationheatfromthecropwillcirculatedustandsporesthroughoutthestore
Figure 51 Vacuuming of potato store
17S T O R E m a n a g E R S rsquo g U I D E
StorEHYGIEnE
Post-storagecleaning
bullStore-cleaningshouldbeundertakenannuallyInboxstoresthisisbestcarriedoutimmediatelyafterthelastcrophasbeenremovedsocleanedboxescanbereturnedtostore
bullInayearfollowingcropinfectionbysilverscurforskinspotextrarigorouscleaningshouldbecarriedout
bullVacuumdirtanddebrisfromfloorsledgesbeamsandotherhorizontalsurfaces
bullWhereinsulationisdamagedorisroughandcollectsdustrepairandvacuum
bullOnlypowerhoseifinsulationismoisture-proof
Cleaningboxes
bullEnsurethatbox-tippersongradinglinesaredesignedtodischargethetotalboxcontentstogetridofmajorcontamination
bullUsepowerhosetocleanboxes
bullWherecleaningboxesisroutineconsidersettingupaconveyor-basedautomaticwashingsystem
bullPower-washboxesforhighhealthcrops
bullWherepossiblereturncleanedboxestostoreorkeepundercoverasthiscanextendboxlifeby70
Whentousedisinfectants
Forhighhealthseedcropsdisinfectantsmaybebeneficialespeciallyafteracontaminatedcropinthepreviousyear
bullUsedisinfectantmistfogorsprayaftervacuumingstore
bullSpraydisinfectboxeswhichhelddiseasedcropout-gradesorlsquobrockrsquo
bullFollowinggradingofdiseasedpotatoespower-washgradinglinethenspraywithdisinfectantwheregradinghighhealthcrops
bullAlwaysuseapprovedproductsandseekspecialistadvice
notesomedisinfectantsmaydamagestoreinsulationandelectricalfittingsndashconsulttheproductlabelbeforeuse
dailycleaning
bullVacuumthefloorparticularlyforkliftroutesandundergradersatleastonceaday
Gradinginstore
GradinginstoreislikelytoincreasetheamountofcontaminateddustinthestoreandthelikelihoodofambientairenteringthroughopendoorsDustprovidesdiseaseinoculumwhileambientairmaycausecondensationparticularlyonthetopsurfaceofboxesorpile
bullIdeallygradeinseparatebuildingwithaplasticstripdoorbetweenthestoreandgradingarea
bullIfgradinginstoreisunavoidableenclosepickersinwarmedcabinandfitadustcontrolsystemtotheline
bullFitdewpointtemperaturemonitortowarnofcondensationrisks
ACTION POINTS
LeavingboxesoutsidewillallowlighttokillviablesporesBoxesshouldnotbestackedmorethanfourboxeshighforsafetyandifstackedinpairsasmallgapbetweenrowswillallownatural(ultraviolet)lighttoreachonesideofeveryboxHoweveroutsidestackingcanreduceboxlifebyupto40
CleaningandenergyefficiencyMaintainingfansventilationandrefrigerationequipmentinacleanconditionwillhelpprolongtheirworkinglifeand
improvetheirworkingefficiencyEnsurethattemperatureandhumidityprobesarekeptcleanandinspectlouvresevaporatorsandcondensersIfnecessarycleanbyvacuumingorpowerwashingIfwashingtakecarearoundelectricalandmovingsystemsandensurethatanyresultingiceisremovedbydefrosting
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
12 S T O R E m a n a g E R S rsquo g U I D E
AllotherthingsbeingequalmoisturelossisafunctionofstorehumidityandairflowratePotatostoreswillusuallysettletoapproximately98relativehumidityandintheabsenceofahumidificationsystemthiswillbederivedbyevaporationofmoisturefromtubersInappropriatelyspecifiedrefrigerationunitscanexacerbatemoistureloss
dormancyFreshlyharvestedtubersusuallydonotsproutevenwhenconditionsareoptimalforsproutgrowthTheperiodoverwhichsproutgrowthisinhibitedbytuberphysiologyratherthanenvironmentalreasonsistermedthedormantperiodorsimplylsquodormancyrsquo
LargedifferencesindormancyoccurbetweenvarietiesWarmstoragetemperatureshaveadormancy-breakingeffectSelectionofvarietiesbydormancycharacteristicscanbeusefulforminimisingsprout-suppressantinputs
Dormancybreakistakenasthepointwhere50oftubershavesproutsof3mmormoreinlengthWarmdrysummerstendtoreducedormancy(inextremecasesleadingtosproutgrowthinthefieldbeforeharvest)whilecoolgrowingconditionswillgenerallyprolongitWaterlogginghasadormancy-breakingeffect
Woundhealing(curing)Wheretubershavebeensubjectedtowounding(egbyhandlingduringharvest)thetuberwillattempttohealthewoundndashaprocessinvolvingsuberisationandcell-divisionThespeedofthisprocesswhichisimportantforpreventingmoisturelossanddiseaseingressisaffectedbyanumberoffactorsTheseincludestoragetemperatureandhumiditywithwarmertemperaturesandhigherhumidityreducingthetimerequiredforwound-healing
Althougheffectivewound-healingisimportantconditionsthatareoptimalforcuringmayalsobesuitablefordiseasedevelopmentWherecropsareharvestedearlyundergoodconditionsorwherethestoragedurationislimitedsufficientcuringmayoccurduringtheperiodoverwhichcroptemperatureisreducedtotheholdingvalueP11
3 Cropphysiology
respirationPotatotubersarelivingorganismsandinstorecontinuetorespireandrespondtotheirenvironmentTheydosobyusingsugarsfromstarchinrespirationThisprocessconsumesoxygenandreleasescarbondioxideandsomeheatenergywhichimpactonstoragesystems
Respirationishighestatharvestandfallsrapidlytoabasallevelinthefirstweeksofstorage(Figure31)Respirationisgreaterinearly-liftedimmaturecropsthaninlate-liftedmaturecrops
Basalrespirationratedependspredominantlyonstoragetemperature(Figure32)Minimumrespirationrateisachievedataround5oCwiththerateincreasingaboveorbelowthistemperature
Handlingmechanicaldamageexposuretoethyleneandsproutingwillleadtoanincreaseinrespirationrate
EvaporationAlthoughsomemoistureislostintheprocessofrespirationmostislostbysimpleevaporationfromthetubersurfaceEffectivewound-healingandsproutcontrolisimportantinlimitingmoisturelossfromtubers
Figure 31 Respiration after lifting ndash early harvest
Figure 33 Moisture exchange between tuber skin and surrounding air in balance at ~98 relative humidity
Figure 32 Respiration in relation to storage temperature
1 2 3 4 5 6 7 8 9 10
Hea
t out
put (
Wto
nne)
35
0
5
10
15
20
25
30
Harvest date 9 September
Days after harvest
Harvest date 20 October
5 15 25
Rat
e of
resp
iratio
n (m
g C
O2k
ghr
)
12
0
2
4
6
8
10
Storage temperature (˚C)
13S T O R E m a n a g E R S rsquo g U I D E
ThisisaccomplishedsimplybyincreasingstoragetemperatureHoweverreconditioningleadstovariabilityinfrycolourandisthereforenotrecommendedasaroutinestoragepractice
PreconditioningmayalsobeusedtomaintainprocessingqualityHeretherearenodistinctcuringpull-downholdingperiodsandfrycolourorsugarcontentisusedtodeterminecropstoragetemperatureTemperaturereductiontoatargetholdingvalueonlyoccursprovidinggoodprocessingqualityismaintained
GreeningandglycoalkaloidsTubersexposedtolightwillturngreenwhichresultsfromthesynthesisofchlorophyllChlorophyllisitselfharmlessbutgreentubersaregenerallyrejectedbecausetheyhaveelevatedlevelsofglycoalkaloidsagroupofnaturaltoxicantspresentinpotatoes
TopreventgreeninginstorageexposuretolightshouldthereforebeminimisedalthoughtheneedtoseethecropclearlyandhealthandsafetyrequirementsP21willoverridethisduringloadingandsubsequentshortperiodswhenstoresareaccessedtobeinspectedorsampled
SugarsandconditioningPotatoescontainthreemainsugarsglucoseandfructose(monosaccharides)andsucrose(adisaccharide)AllthreesugarsaresweetandareimportantflavourcomponentsinwarepotatoesInpotatoesforprocessingthestoremanagerisprimarilyinterestedinthemonosaccharidesDuringprocessingthesereactwithothercomponentstoproducethebrowningwhichisassessedbymarketsasfrycolourAstoremanagersupplyingcropforprocessingmayalsobeinterestedinsucrosecontentAlthoughsucrosedoesnottakepartinbrowningreactionstrendsinsucroselevelsmaybeusedtohelpensurelowreducingsugarsandlightfrycolourduringstorage
VarietygrowthstageandstoragetemperatureareimportantindeterminingtubersugarcontentPotatoesexhibitlowtemperature-sweeteningwheresugarsaccumulatewithinthetuberastemperatureisreducedDuringstorageforprocessingtemperatureshouldthereforebemaintainedatthelowestlevelthatsafelymaintainsacceptablefrycolour
Forprocessingcropschangesinsugarcontent(andhencefrycolour)canbeachievedusingreconditioning
respiration
Thegreatertherespirationrateofthepotatoesthemorelikelyitisthatwarmairwillcondenseoncoolersurfacepotatoes
bullPositivelyventilatepotatoestoremoverespirationheattopreventsurfacecondensation
bullUsehighventilationratestopreventcondensationinheavilyrespiringearly-liftedorimmaturecropsP11
Evaporation
Moisturelossfrompotatoesduetoevaporationwilloccuriftherelativehumidity(RH)oftheairsurroundingthepotatoesislessthan98
bullKeepstorewell-sealedtominimiseweightloss
bullPreventuncontrolledexternalairingressasthisusuallyhasalowerRHthanthestorageenvironment
Sugars
Sugarsincreaseandfrycolourswilldarkenifpotatoesarestoredatcoldtemperatures
bullStorecropsforprocessingatc7-10degC
bullMonitorcold-storedpre-packpotatoesforeffectsofsugarincreaseontaste
bullIfunsurecheckstoragerequirementswithyourcustomer
ACTION POINTS
CroPPHYSIoLoGY
14 S T O R E m a n a g E R S rsquo g U I D E
Silverscurf Blackdot Skinspot dryrot Gangrene Softrot
moderateinfection
severeinfection
4 Controlofstoragediseases
DiseasecontrolisafundamentalcomponentofstoragemanagementMostdiseasesdonotoriginateinstoretheycomefromtwoprimarysourcestheseedorthesoilHowevermanyofthediseaseproblemsaffectingthepremiummarketscandeveloptosomedegreeinstoreandifnotcontrolledtheconsequencescanbecatastrophiceitherintermsofphysicalbreakdownofthecroporinlossofmarketvalueWhetherdiseasewilldevelopinstoreornot(Figure41)dependson
bullTheamountofinoculumusuallysporesorbacteriapresentonthetubersbullWhethermoisturenutrientsandtemperaturearesuitableforthediseasetogrowbullThenaturalresistanceofthetubertothediseaseorganism
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
15S T O R E m a n a g E R S rsquo g U I D E
Storemanagementallowsustoinfluencethisrelationshipparticularlyinrelationtothemicro-climatearoundthetubertocontroldiseasesduringstorage
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
Micro-climate Tuberresistance
Inoculum
Figure 41 Interaction between micro-climate and disease
notifiablediseases
SomediseasesarenotindigenousinBritainandtheirestablishmentwouldaffectthelong-termviabilityofthepotatoindustryIfsymptomsofeitherbrownrotorringrotaresuspectedthenimmediatecontactwithlocalDEFRAofficesorPlantHealthandSeedinspectorateisnecessaryVisitwwwdefragovukplanthphhtmemailplanthealthinfodefragsigovukortelephone01904455174toreportsuspectedcasesinEnglandandWalesInScotlandvisitwwwsasagovukplant_health
PreventativemeasuresexistGotowwwpotatoorguksafehaventolearnmoreaboutnationalschemesthatprotectseedandwarecrophealth
ringrotBrownrot
16 S T O R E m a n a g E R S rsquo g U I D E
Figure 52 Ensure dust and debris are removed from ducts
CrosscontaminationofsporesbetweenpotatostocksisinevitableFanventilationwithinthestoremayincreasethespeedofthismovementcomparedwithnaturalconvectionButtheairflowisabenefitasithelpskeepthecropfreefromcondensationpreventinganysporeswhichdosettlefromgerminating
MajordustmovementanddispersaloccurswhenforklifttrucksstirupdustonthefloorduringhandlingTheresultantdustcloudwillsettleontopofthecropwherethecondensationneededforgerminationismostlikelyIfgradingiscarriedoutwithinthestorethiswillalsocreateaconsiderabledustcloudwithsimilarconsequences
dustremovalSweepingwithabrushmovestheheavierdustparticlesalongthefloorwhilecreatingacloudoflighterparticleswhichincludesthemajorityofsporesVacuumingloosensandremovesallfractionsofdustandiffittedwithafinefilterwillremovemostharmfulsporesfromthestoreVacuumingisthereforemuchpreferredtosweeping
disinfectionRemovingdustandsquashedtuberswillremovethemajorityofinoculumpresentSomedustandsporeswillremainonthefloorwallsandraftersaswellasthefloorandsidesofpotatoboxesthemajorityofwhichcanberemovedbypowerwashingIftotalremovalofviablesporesisrequiredegforhighhealthcropsadisinfectantcanbeusedThisisparticularlyrelevantinstoreswheredamagerelateddiseasessuchasdryrothaveoccurred
5 Storehygiene
AcleanstorefreefromdiscardedtubersdustanddebrishasanumberofadvantagesItwillminimisecropinfectionimproveairflowcontributetoworkerhealthandcomfortandislikelytoimpressclientsandcustomers
SomesoilisinevitablybroughtintostorewiththeharvestedcropOncedrythisbecomesapotentialsourceofdustwhenthecropismovedIfthecropisfreeofdiseasewhenharvestedanditremainssooverthestorageperiodthenthedustwillbemainlymineralinnatureHoweverifthecropisdiseasedorbecomessoduringstoragethedustmaycontainlargequantitiesofsporeswhichwillbeasourceofinoculuminthepresentorfutureyears
dustdispersalConvectioncurrentscausedbyrespirationheatfromthecropwillcirculatedustandsporesthroughoutthestore
Figure 51 Vacuuming of potato store
17S T O R E m a n a g E R S rsquo g U I D E
StorEHYGIEnE
Post-storagecleaning
bullStore-cleaningshouldbeundertakenannuallyInboxstoresthisisbestcarriedoutimmediatelyafterthelastcrophasbeenremovedsocleanedboxescanbereturnedtostore
bullInayearfollowingcropinfectionbysilverscurforskinspotextrarigorouscleaningshouldbecarriedout
bullVacuumdirtanddebrisfromfloorsledgesbeamsandotherhorizontalsurfaces
bullWhereinsulationisdamagedorisroughandcollectsdustrepairandvacuum
bullOnlypowerhoseifinsulationismoisture-proof
Cleaningboxes
bullEnsurethatbox-tippersongradinglinesaredesignedtodischargethetotalboxcontentstogetridofmajorcontamination
bullUsepowerhosetocleanboxes
bullWherecleaningboxesisroutineconsidersettingupaconveyor-basedautomaticwashingsystem
bullPower-washboxesforhighhealthcrops
bullWherepossiblereturncleanedboxestostoreorkeepundercoverasthiscanextendboxlifeby70
Whentousedisinfectants
Forhighhealthseedcropsdisinfectantsmaybebeneficialespeciallyafteracontaminatedcropinthepreviousyear
bullUsedisinfectantmistfogorsprayaftervacuumingstore
bullSpraydisinfectboxeswhichhelddiseasedcropout-gradesorlsquobrockrsquo
bullFollowinggradingofdiseasedpotatoespower-washgradinglinethenspraywithdisinfectantwheregradinghighhealthcrops
bullAlwaysuseapprovedproductsandseekspecialistadvice
notesomedisinfectantsmaydamagestoreinsulationandelectricalfittingsndashconsulttheproductlabelbeforeuse
dailycleaning
bullVacuumthefloorparticularlyforkliftroutesandundergradersatleastonceaday
Gradinginstore
GradinginstoreislikelytoincreasetheamountofcontaminateddustinthestoreandthelikelihoodofambientairenteringthroughopendoorsDustprovidesdiseaseinoculumwhileambientairmaycausecondensationparticularlyonthetopsurfaceofboxesorpile
bullIdeallygradeinseparatebuildingwithaplasticstripdoorbetweenthestoreandgradingarea
bullIfgradinginstoreisunavoidableenclosepickersinwarmedcabinandfitadustcontrolsystemtotheline
bullFitdewpointtemperaturemonitortowarnofcondensationrisks
ACTION POINTS
LeavingboxesoutsidewillallowlighttokillviablesporesBoxesshouldnotbestackedmorethanfourboxeshighforsafetyandifstackedinpairsasmallgapbetweenrowswillallownatural(ultraviolet)lighttoreachonesideofeveryboxHoweveroutsidestackingcanreduceboxlifebyupto40
CleaningandenergyefficiencyMaintainingfansventilationandrefrigerationequipmentinacleanconditionwillhelpprolongtheirworkinglifeand
improvetheirworkingefficiencyEnsurethattemperatureandhumidityprobesarekeptcleanandinspectlouvresevaporatorsandcondensersIfnecessarycleanbyvacuumingorpowerwashingIfwashingtakecarearoundelectricalandmovingsystemsandensurethatanyresultingiceisremovedbydefrosting
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
13S T O R E m a n a g E R S rsquo g U I D E
ThisisaccomplishedsimplybyincreasingstoragetemperatureHoweverreconditioningleadstovariabilityinfrycolourandisthereforenotrecommendedasaroutinestoragepractice
PreconditioningmayalsobeusedtomaintainprocessingqualityHeretherearenodistinctcuringpull-downholdingperiodsandfrycolourorsugarcontentisusedtodeterminecropstoragetemperatureTemperaturereductiontoatargetholdingvalueonlyoccursprovidinggoodprocessingqualityismaintained
GreeningandglycoalkaloidsTubersexposedtolightwillturngreenwhichresultsfromthesynthesisofchlorophyllChlorophyllisitselfharmlessbutgreentubersaregenerallyrejectedbecausetheyhaveelevatedlevelsofglycoalkaloidsagroupofnaturaltoxicantspresentinpotatoes
TopreventgreeninginstorageexposuretolightshouldthereforebeminimisedalthoughtheneedtoseethecropclearlyandhealthandsafetyrequirementsP21willoverridethisduringloadingandsubsequentshortperiodswhenstoresareaccessedtobeinspectedorsampled
SugarsandconditioningPotatoescontainthreemainsugarsglucoseandfructose(monosaccharides)andsucrose(adisaccharide)AllthreesugarsaresweetandareimportantflavourcomponentsinwarepotatoesInpotatoesforprocessingthestoremanagerisprimarilyinterestedinthemonosaccharidesDuringprocessingthesereactwithothercomponentstoproducethebrowningwhichisassessedbymarketsasfrycolourAstoremanagersupplyingcropforprocessingmayalsobeinterestedinsucrosecontentAlthoughsucrosedoesnottakepartinbrowningreactionstrendsinsucroselevelsmaybeusedtohelpensurelowreducingsugarsandlightfrycolourduringstorage
VarietygrowthstageandstoragetemperatureareimportantindeterminingtubersugarcontentPotatoesexhibitlowtemperature-sweeteningwheresugarsaccumulatewithinthetuberastemperatureisreducedDuringstorageforprocessingtemperatureshouldthereforebemaintainedatthelowestlevelthatsafelymaintainsacceptablefrycolour
Forprocessingcropschangesinsugarcontent(andhencefrycolour)canbeachievedusingreconditioning
respiration
Thegreatertherespirationrateofthepotatoesthemorelikelyitisthatwarmairwillcondenseoncoolersurfacepotatoes
bullPositivelyventilatepotatoestoremoverespirationheattopreventsurfacecondensation
bullUsehighventilationratestopreventcondensationinheavilyrespiringearly-liftedorimmaturecropsP11
Evaporation
Moisturelossfrompotatoesduetoevaporationwilloccuriftherelativehumidity(RH)oftheairsurroundingthepotatoesislessthan98
bullKeepstorewell-sealedtominimiseweightloss
bullPreventuncontrolledexternalairingressasthisusuallyhasalowerRHthanthestorageenvironment
Sugars
Sugarsincreaseandfrycolourswilldarkenifpotatoesarestoredatcoldtemperatures
bullStorecropsforprocessingatc7-10degC
bullMonitorcold-storedpre-packpotatoesforeffectsofsugarincreaseontaste
bullIfunsurecheckstoragerequirementswithyourcustomer
ACTION POINTS
CroPPHYSIoLoGY
14 S T O R E m a n a g E R S rsquo g U I D E
Silverscurf Blackdot Skinspot dryrot Gangrene Softrot
moderateinfection
severeinfection
4 Controlofstoragediseases
DiseasecontrolisafundamentalcomponentofstoragemanagementMostdiseasesdonotoriginateinstoretheycomefromtwoprimarysourcestheseedorthesoilHowevermanyofthediseaseproblemsaffectingthepremiummarketscandeveloptosomedegreeinstoreandifnotcontrolledtheconsequencescanbecatastrophiceitherintermsofphysicalbreakdownofthecroporinlossofmarketvalueWhetherdiseasewilldevelopinstoreornot(Figure41)dependson
bullTheamountofinoculumusuallysporesorbacteriapresentonthetubersbullWhethermoisturenutrientsandtemperaturearesuitableforthediseasetogrowbullThenaturalresistanceofthetubertothediseaseorganism
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
15S T O R E m a n a g E R S rsquo g U I D E
Storemanagementallowsustoinfluencethisrelationshipparticularlyinrelationtothemicro-climatearoundthetubertocontroldiseasesduringstorage
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
Micro-climate Tuberresistance
Inoculum
Figure 41 Interaction between micro-climate and disease
notifiablediseases
SomediseasesarenotindigenousinBritainandtheirestablishmentwouldaffectthelong-termviabilityofthepotatoindustryIfsymptomsofeitherbrownrotorringrotaresuspectedthenimmediatecontactwithlocalDEFRAofficesorPlantHealthandSeedinspectorateisnecessaryVisitwwwdefragovukplanthphhtmemailplanthealthinfodefragsigovukortelephone01904455174toreportsuspectedcasesinEnglandandWalesInScotlandvisitwwwsasagovukplant_health
PreventativemeasuresexistGotowwwpotatoorguksafehaventolearnmoreaboutnationalschemesthatprotectseedandwarecrophealth
ringrotBrownrot
16 S T O R E m a n a g E R S rsquo g U I D E
Figure 52 Ensure dust and debris are removed from ducts
CrosscontaminationofsporesbetweenpotatostocksisinevitableFanventilationwithinthestoremayincreasethespeedofthismovementcomparedwithnaturalconvectionButtheairflowisabenefitasithelpskeepthecropfreefromcondensationpreventinganysporeswhichdosettlefromgerminating
MajordustmovementanddispersaloccurswhenforklifttrucksstirupdustonthefloorduringhandlingTheresultantdustcloudwillsettleontopofthecropwherethecondensationneededforgerminationismostlikelyIfgradingiscarriedoutwithinthestorethiswillalsocreateaconsiderabledustcloudwithsimilarconsequences
dustremovalSweepingwithabrushmovestheheavierdustparticlesalongthefloorwhilecreatingacloudoflighterparticleswhichincludesthemajorityofsporesVacuumingloosensandremovesallfractionsofdustandiffittedwithafinefilterwillremovemostharmfulsporesfromthestoreVacuumingisthereforemuchpreferredtosweeping
disinfectionRemovingdustandsquashedtuberswillremovethemajorityofinoculumpresentSomedustandsporeswillremainonthefloorwallsandraftersaswellasthefloorandsidesofpotatoboxesthemajorityofwhichcanberemovedbypowerwashingIftotalremovalofviablesporesisrequiredegforhighhealthcropsadisinfectantcanbeusedThisisparticularlyrelevantinstoreswheredamagerelateddiseasessuchasdryrothaveoccurred
5 Storehygiene
AcleanstorefreefromdiscardedtubersdustanddebrishasanumberofadvantagesItwillminimisecropinfectionimproveairflowcontributetoworkerhealthandcomfortandislikelytoimpressclientsandcustomers
SomesoilisinevitablybroughtintostorewiththeharvestedcropOncedrythisbecomesapotentialsourceofdustwhenthecropismovedIfthecropisfreeofdiseasewhenharvestedanditremainssooverthestorageperiodthenthedustwillbemainlymineralinnatureHoweverifthecropisdiseasedorbecomessoduringstoragethedustmaycontainlargequantitiesofsporeswhichwillbeasourceofinoculuminthepresentorfutureyears
dustdispersalConvectioncurrentscausedbyrespirationheatfromthecropwillcirculatedustandsporesthroughoutthestore
Figure 51 Vacuuming of potato store
17S T O R E m a n a g E R S rsquo g U I D E
StorEHYGIEnE
Post-storagecleaning
bullStore-cleaningshouldbeundertakenannuallyInboxstoresthisisbestcarriedoutimmediatelyafterthelastcrophasbeenremovedsocleanedboxescanbereturnedtostore
bullInayearfollowingcropinfectionbysilverscurforskinspotextrarigorouscleaningshouldbecarriedout
bullVacuumdirtanddebrisfromfloorsledgesbeamsandotherhorizontalsurfaces
bullWhereinsulationisdamagedorisroughandcollectsdustrepairandvacuum
bullOnlypowerhoseifinsulationismoisture-proof
Cleaningboxes
bullEnsurethatbox-tippersongradinglinesaredesignedtodischargethetotalboxcontentstogetridofmajorcontamination
bullUsepowerhosetocleanboxes
bullWherecleaningboxesisroutineconsidersettingupaconveyor-basedautomaticwashingsystem
bullPower-washboxesforhighhealthcrops
bullWherepossiblereturncleanedboxestostoreorkeepundercoverasthiscanextendboxlifeby70
Whentousedisinfectants
Forhighhealthseedcropsdisinfectantsmaybebeneficialespeciallyafteracontaminatedcropinthepreviousyear
bullUsedisinfectantmistfogorsprayaftervacuumingstore
bullSpraydisinfectboxeswhichhelddiseasedcropout-gradesorlsquobrockrsquo
bullFollowinggradingofdiseasedpotatoespower-washgradinglinethenspraywithdisinfectantwheregradinghighhealthcrops
bullAlwaysuseapprovedproductsandseekspecialistadvice
notesomedisinfectantsmaydamagestoreinsulationandelectricalfittingsndashconsulttheproductlabelbeforeuse
dailycleaning
bullVacuumthefloorparticularlyforkliftroutesandundergradersatleastonceaday
Gradinginstore
GradinginstoreislikelytoincreasetheamountofcontaminateddustinthestoreandthelikelihoodofambientairenteringthroughopendoorsDustprovidesdiseaseinoculumwhileambientairmaycausecondensationparticularlyonthetopsurfaceofboxesorpile
bullIdeallygradeinseparatebuildingwithaplasticstripdoorbetweenthestoreandgradingarea
bullIfgradinginstoreisunavoidableenclosepickersinwarmedcabinandfitadustcontrolsystemtotheline
bullFitdewpointtemperaturemonitortowarnofcondensationrisks
ACTION POINTS
LeavingboxesoutsidewillallowlighttokillviablesporesBoxesshouldnotbestackedmorethanfourboxeshighforsafetyandifstackedinpairsasmallgapbetweenrowswillallownatural(ultraviolet)lighttoreachonesideofeveryboxHoweveroutsidestackingcanreduceboxlifebyupto40
CleaningandenergyefficiencyMaintainingfansventilationandrefrigerationequipmentinacleanconditionwillhelpprolongtheirworkinglifeand
improvetheirworkingefficiencyEnsurethattemperatureandhumidityprobesarekeptcleanandinspectlouvresevaporatorsandcondensersIfnecessarycleanbyvacuumingorpowerwashingIfwashingtakecarearoundelectricalandmovingsystemsandensurethatanyresultingiceisremovedbydefrosting
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
14 S T O R E m a n a g E R S rsquo g U I D E
Silverscurf Blackdot Skinspot dryrot Gangrene Softrot
moderateinfection
severeinfection
4 Controlofstoragediseases
DiseasecontrolisafundamentalcomponentofstoragemanagementMostdiseasesdonotoriginateinstoretheycomefromtwoprimarysourcestheseedorthesoilHowevermanyofthediseaseproblemsaffectingthepremiummarketscandeveloptosomedegreeinstoreandifnotcontrolledtheconsequencescanbecatastrophiceitherintermsofphysicalbreakdownofthecroporinlossofmarketvalueWhetherdiseasewilldevelopinstoreornot(Figure41)dependson
bullTheamountofinoculumusuallysporesorbacteriapresentonthetubersbullWhethermoisturenutrientsandtemperaturearesuitableforthediseasetogrowbullThenaturalresistanceofthetubertothediseaseorganism
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
15S T O R E m a n a g E R S rsquo g U I D E
Storemanagementallowsustoinfluencethisrelationshipparticularlyinrelationtothemicro-climatearoundthetubertocontroldiseasesduringstorage
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
Micro-climate Tuberresistance
Inoculum
Figure 41 Interaction between micro-climate and disease
notifiablediseases
SomediseasesarenotindigenousinBritainandtheirestablishmentwouldaffectthelong-termviabilityofthepotatoindustryIfsymptomsofeitherbrownrotorringrotaresuspectedthenimmediatecontactwithlocalDEFRAofficesorPlantHealthandSeedinspectorateisnecessaryVisitwwwdefragovukplanthphhtmemailplanthealthinfodefragsigovukortelephone01904455174toreportsuspectedcasesinEnglandandWalesInScotlandvisitwwwsasagovukplant_health
PreventativemeasuresexistGotowwwpotatoorguksafehaventolearnmoreaboutnationalschemesthatprotectseedandwarecrophealth
ringrotBrownrot
16 S T O R E m a n a g E R S rsquo g U I D E
Figure 52 Ensure dust and debris are removed from ducts
CrosscontaminationofsporesbetweenpotatostocksisinevitableFanventilationwithinthestoremayincreasethespeedofthismovementcomparedwithnaturalconvectionButtheairflowisabenefitasithelpskeepthecropfreefromcondensationpreventinganysporeswhichdosettlefromgerminating
MajordustmovementanddispersaloccurswhenforklifttrucksstirupdustonthefloorduringhandlingTheresultantdustcloudwillsettleontopofthecropwherethecondensationneededforgerminationismostlikelyIfgradingiscarriedoutwithinthestorethiswillalsocreateaconsiderabledustcloudwithsimilarconsequences
dustremovalSweepingwithabrushmovestheheavierdustparticlesalongthefloorwhilecreatingacloudoflighterparticleswhichincludesthemajorityofsporesVacuumingloosensandremovesallfractionsofdustandiffittedwithafinefilterwillremovemostharmfulsporesfromthestoreVacuumingisthereforemuchpreferredtosweeping
disinfectionRemovingdustandsquashedtuberswillremovethemajorityofinoculumpresentSomedustandsporeswillremainonthefloorwallsandraftersaswellasthefloorandsidesofpotatoboxesthemajorityofwhichcanberemovedbypowerwashingIftotalremovalofviablesporesisrequiredegforhighhealthcropsadisinfectantcanbeusedThisisparticularlyrelevantinstoreswheredamagerelateddiseasessuchasdryrothaveoccurred
5 Storehygiene
AcleanstorefreefromdiscardedtubersdustanddebrishasanumberofadvantagesItwillminimisecropinfectionimproveairflowcontributetoworkerhealthandcomfortandislikelytoimpressclientsandcustomers
SomesoilisinevitablybroughtintostorewiththeharvestedcropOncedrythisbecomesapotentialsourceofdustwhenthecropismovedIfthecropisfreeofdiseasewhenharvestedanditremainssooverthestorageperiodthenthedustwillbemainlymineralinnatureHoweverifthecropisdiseasedorbecomessoduringstoragethedustmaycontainlargequantitiesofsporeswhichwillbeasourceofinoculuminthepresentorfutureyears
dustdispersalConvectioncurrentscausedbyrespirationheatfromthecropwillcirculatedustandsporesthroughoutthestore
Figure 51 Vacuuming of potato store
17S T O R E m a n a g E R S rsquo g U I D E
StorEHYGIEnE
Post-storagecleaning
bullStore-cleaningshouldbeundertakenannuallyInboxstoresthisisbestcarriedoutimmediatelyafterthelastcrophasbeenremovedsocleanedboxescanbereturnedtostore
bullInayearfollowingcropinfectionbysilverscurforskinspotextrarigorouscleaningshouldbecarriedout
bullVacuumdirtanddebrisfromfloorsledgesbeamsandotherhorizontalsurfaces
bullWhereinsulationisdamagedorisroughandcollectsdustrepairandvacuum
bullOnlypowerhoseifinsulationismoisture-proof
Cleaningboxes
bullEnsurethatbox-tippersongradinglinesaredesignedtodischargethetotalboxcontentstogetridofmajorcontamination
bullUsepowerhosetocleanboxes
bullWherecleaningboxesisroutineconsidersettingupaconveyor-basedautomaticwashingsystem
bullPower-washboxesforhighhealthcrops
bullWherepossiblereturncleanedboxestostoreorkeepundercoverasthiscanextendboxlifeby70
Whentousedisinfectants
Forhighhealthseedcropsdisinfectantsmaybebeneficialespeciallyafteracontaminatedcropinthepreviousyear
bullUsedisinfectantmistfogorsprayaftervacuumingstore
bullSpraydisinfectboxeswhichhelddiseasedcropout-gradesorlsquobrockrsquo
bullFollowinggradingofdiseasedpotatoespower-washgradinglinethenspraywithdisinfectantwheregradinghighhealthcrops
bullAlwaysuseapprovedproductsandseekspecialistadvice
notesomedisinfectantsmaydamagestoreinsulationandelectricalfittingsndashconsulttheproductlabelbeforeuse
dailycleaning
bullVacuumthefloorparticularlyforkliftroutesandundergradersatleastonceaday
Gradinginstore
GradinginstoreislikelytoincreasetheamountofcontaminateddustinthestoreandthelikelihoodofambientairenteringthroughopendoorsDustprovidesdiseaseinoculumwhileambientairmaycausecondensationparticularlyonthetopsurfaceofboxesorpile
bullIdeallygradeinseparatebuildingwithaplasticstripdoorbetweenthestoreandgradingarea
bullIfgradinginstoreisunavoidableenclosepickersinwarmedcabinandfitadustcontrolsystemtotheline
bullFitdewpointtemperaturemonitortowarnofcondensationrisks
ACTION POINTS
LeavingboxesoutsidewillallowlighttokillviablesporesBoxesshouldnotbestackedmorethanfourboxeshighforsafetyandifstackedinpairsasmallgapbetweenrowswillallownatural(ultraviolet)lighttoreachonesideofeveryboxHoweveroutsidestackingcanreduceboxlifebyupto40
CleaningandenergyefficiencyMaintainingfansventilationandrefrigerationequipmentinacleanconditionwillhelpprolongtheirworkinglifeand
improvetheirworkingefficiencyEnsurethattemperatureandhumidityprobesarekeptcleanandinspectlouvresevaporatorsandcondensersIfnecessarycleanbyvacuumingorpowerwashingIfwashingtakecarearoundelectricalandmovingsystemsandensurethatanyresultingiceisremovedbydefrosting
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
15S T O R E m a n a g E R S rsquo g U I D E
Storemanagementallowsustoinfluencethisrelationshipparticularlyinrelationtothemicro-climatearoundthetubertocontroldiseasesduringstorage
PrE-StorAGEControLMEASurES notES
Healthyseed Useofcertifiedseedpreferredwherepossible
Widerotations Diseasecansurviveintheabsenceofapotatocropbutwillusuallydeclineovertime Afivesixyearbreakisusuallyeffective
Shortgrowingseasons Typicallythelongerpotatoesstayinthegroundthemorediseaseislikelytodevelop Dryrotisanexceptionandmaybemoreofaproblemforcropsliftedinsummer
Earlyharvest Oncedesiccatedorsenescedcropsmaybecomepredisposedtodiseaseslikeblackdot Rapidharvestisencouragedprovidingadequateskinsethasbeenachieved
Resistantvariety Forinvasivediseaseslikeskinspotandgangrenevarietalresistancedecreasesthelikelihoodofdiseasedevelopment Usevarietydatabasewwwpotatoorgukvarieties
Minimisedamage Openwoundsifleftuntreatedallowrapidaccessforrottingdiseases
Dryharvestconditions Manydiseasesdevelopmorerapidlywhenfreemoistureisavailable
MEASurESForControLInStorAGE
Curing Woundhealingisessentialtopreventdevelopmentofinvasivediseasessuchasgangreneanddryrotbuthigh temperatureusemayencouragedevelopmentofsilverscurfblackdotandsoftrotting
Immediatepull-down Wherewoundhealingisnotessential(lowdamage)immediatepull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Rapidpull-down Wherewoundhealingisnotessentialafastrateofpull-downcanreducetheriskofblackdot silverscurfandsoftrotting
Lowtemperature(holding) Manydiseasesdevelopatwarmertemperaturesthiscanberestrictedatlowertemperatures Exceptionsareskinspotandgangrenewherethetuberrsquosdefencemechanismsarepooratlowtemperatures
Minimisegradingdamage Warming(to8degC)priortogradingwillhelpminimisedamageandreduceopportunityforinvasivediseasestodevelop
Storehygiene Regularstorehygienewillhelpremovesporesandfungalfragmentsofmostpathogens
Boxampgraderhygiene Woundorrottingdiseasescanbeconsideredstubbornastheycanpersistongradinglinesorboxes Identifyingandcleaningcontaminatedareaswillreducerisk
Micro-climate Tuberresistance
Inoculum
Figure 41 Interaction between micro-climate and disease
notifiablediseases
SomediseasesarenotindigenousinBritainandtheirestablishmentwouldaffectthelong-termviabilityofthepotatoindustryIfsymptomsofeitherbrownrotorringrotaresuspectedthenimmediatecontactwithlocalDEFRAofficesorPlantHealthandSeedinspectorateisnecessaryVisitwwwdefragovukplanthphhtmemailplanthealthinfodefragsigovukortelephone01904455174toreportsuspectedcasesinEnglandandWalesInScotlandvisitwwwsasagovukplant_health
PreventativemeasuresexistGotowwwpotatoorguksafehaventolearnmoreaboutnationalschemesthatprotectseedandwarecrophealth
ringrotBrownrot
16 S T O R E m a n a g E R S rsquo g U I D E
Figure 52 Ensure dust and debris are removed from ducts
CrosscontaminationofsporesbetweenpotatostocksisinevitableFanventilationwithinthestoremayincreasethespeedofthismovementcomparedwithnaturalconvectionButtheairflowisabenefitasithelpskeepthecropfreefromcondensationpreventinganysporeswhichdosettlefromgerminating
MajordustmovementanddispersaloccurswhenforklifttrucksstirupdustonthefloorduringhandlingTheresultantdustcloudwillsettleontopofthecropwherethecondensationneededforgerminationismostlikelyIfgradingiscarriedoutwithinthestorethiswillalsocreateaconsiderabledustcloudwithsimilarconsequences
dustremovalSweepingwithabrushmovestheheavierdustparticlesalongthefloorwhilecreatingacloudoflighterparticleswhichincludesthemajorityofsporesVacuumingloosensandremovesallfractionsofdustandiffittedwithafinefilterwillremovemostharmfulsporesfromthestoreVacuumingisthereforemuchpreferredtosweeping
disinfectionRemovingdustandsquashedtuberswillremovethemajorityofinoculumpresentSomedustandsporeswillremainonthefloorwallsandraftersaswellasthefloorandsidesofpotatoboxesthemajorityofwhichcanberemovedbypowerwashingIftotalremovalofviablesporesisrequiredegforhighhealthcropsadisinfectantcanbeusedThisisparticularlyrelevantinstoreswheredamagerelateddiseasessuchasdryrothaveoccurred
5 Storehygiene
AcleanstorefreefromdiscardedtubersdustanddebrishasanumberofadvantagesItwillminimisecropinfectionimproveairflowcontributetoworkerhealthandcomfortandislikelytoimpressclientsandcustomers
SomesoilisinevitablybroughtintostorewiththeharvestedcropOncedrythisbecomesapotentialsourceofdustwhenthecropismovedIfthecropisfreeofdiseasewhenharvestedanditremainssooverthestorageperiodthenthedustwillbemainlymineralinnatureHoweverifthecropisdiseasedorbecomessoduringstoragethedustmaycontainlargequantitiesofsporeswhichwillbeasourceofinoculuminthepresentorfutureyears
dustdispersalConvectioncurrentscausedbyrespirationheatfromthecropwillcirculatedustandsporesthroughoutthestore
Figure 51 Vacuuming of potato store
17S T O R E m a n a g E R S rsquo g U I D E
StorEHYGIEnE
Post-storagecleaning
bullStore-cleaningshouldbeundertakenannuallyInboxstoresthisisbestcarriedoutimmediatelyafterthelastcrophasbeenremovedsocleanedboxescanbereturnedtostore
bullInayearfollowingcropinfectionbysilverscurforskinspotextrarigorouscleaningshouldbecarriedout
bullVacuumdirtanddebrisfromfloorsledgesbeamsandotherhorizontalsurfaces
bullWhereinsulationisdamagedorisroughandcollectsdustrepairandvacuum
bullOnlypowerhoseifinsulationismoisture-proof
Cleaningboxes
bullEnsurethatbox-tippersongradinglinesaredesignedtodischargethetotalboxcontentstogetridofmajorcontamination
bullUsepowerhosetocleanboxes
bullWherecleaningboxesisroutineconsidersettingupaconveyor-basedautomaticwashingsystem
bullPower-washboxesforhighhealthcrops
bullWherepossiblereturncleanedboxestostoreorkeepundercoverasthiscanextendboxlifeby70
Whentousedisinfectants
Forhighhealthseedcropsdisinfectantsmaybebeneficialespeciallyafteracontaminatedcropinthepreviousyear
bullUsedisinfectantmistfogorsprayaftervacuumingstore
bullSpraydisinfectboxeswhichhelddiseasedcropout-gradesorlsquobrockrsquo
bullFollowinggradingofdiseasedpotatoespower-washgradinglinethenspraywithdisinfectantwheregradinghighhealthcrops
bullAlwaysuseapprovedproductsandseekspecialistadvice
notesomedisinfectantsmaydamagestoreinsulationandelectricalfittingsndashconsulttheproductlabelbeforeuse
dailycleaning
bullVacuumthefloorparticularlyforkliftroutesandundergradersatleastonceaday
Gradinginstore
GradinginstoreislikelytoincreasetheamountofcontaminateddustinthestoreandthelikelihoodofambientairenteringthroughopendoorsDustprovidesdiseaseinoculumwhileambientairmaycausecondensationparticularlyonthetopsurfaceofboxesorpile
bullIdeallygradeinseparatebuildingwithaplasticstripdoorbetweenthestoreandgradingarea
bullIfgradinginstoreisunavoidableenclosepickersinwarmedcabinandfitadustcontrolsystemtotheline
bullFitdewpointtemperaturemonitortowarnofcondensationrisks
ACTION POINTS
LeavingboxesoutsidewillallowlighttokillviablesporesBoxesshouldnotbestackedmorethanfourboxeshighforsafetyandifstackedinpairsasmallgapbetweenrowswillallownatural(ultraviolet)lighttoreachonesideofeveryboxHoweveroutsidestackingcanreduceboxlifebyupto40
CleaningandenergyefficiencyMaintainingfansventilationandrefrigerationequipmentinacleanconditionwillhelpprolongtheirworkinglifeand
improvetheirworkingefficiencyEnsurethattemperatureandhumidityprobesarekeptcleanandinspectlouvresevaporatorsandcondensersIfnecessarycleanbyvacuumingorpowerwashingIfwashingtakecarearoundelectricalandmovingsystemsandensurethatanyresultingiceisremovedbydefrosting
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
16 S T O R E m a n a g E R S rsquo g U I D E
Figure 52 Ensure dust and debris are removed from ducts
CrosscontaminationofsporesbetweenpotatostocksisinevitableFanventilationwithinthestoremayincreasethespeedofthismovementcomparedwithnaturalconvectionButtheairflowisabenefitasithelpskeepthecropfreefromcondensationpreventinganysporeswhichdosettlefromgerminating
MajordustmovementanddispersaloccurswhenforklifttrucksstirupdustonthefloorduringhandlingTheresultantdustcloudwillsettleontopofthecropwherethecondensationneededforgerminationismostlikelyIfgradingiscarriedoutwithinthestorethiswillalsocreateaconsiderabledustcloudwithsimilarconsequences
dustremovalSweepingwithabrushmovestheheavierdustparticlesalongthefloorwhilecreatingacloudoflighterparticleswhichincludesthemajorityofsporesVacuumingloosensandremovesallfractionsofdustandiffittedwithafinefilterwillremovemostharmfulsporesfromthestoreVacuumingisthereforemuchpreferredtosweeping
disinfectionRemovingdustandsquashedtuberswillremovethemajorityofinoculumpresentSomedustandsporeswillremainonthefloorwallsandraftersaswellasthefloorandsidesofpotatoboxesthemajorityofwhichcanberemovedbypowerwashingIftotalremovalofviablesporesisrequiredegforhighhealthcropsadisinfectantcanbeusedThisisparticularlyrelevantinstoreswheredamagerelateddiseasessuchasdryrothaveoccurred
5 Storehygiene
AcleanstorefreefromdiscardedtubersdustanddebrishasanumberofadvantagesItwillminimisecropinfectionimproveairflowcontributetoworkerhealthandcomfortandislikelytoimpressclientsandcustomers
SomesoilisinevitablybroughtintostorewiththeharvestedcropOncedrythisbecomesapotentialsourceofdustwhenthecropismovedIfthecropisfreeofdiseasewhenharvestedanditremainssooverthestorageperiodthenthedustwillbemainlymineralinnatureHoweverifthecropisdiseasedorbecomessoduringstoragethedustmaycontainlargequantitiesofsporeswhichwillbeasourceofinoculuminthepresentorfutureyears
dustdispersalConvectioncurrentscausedbyrespirationheatfromthecropwillcirculatedustandsporesthroughoutthestore
Figure 51 Vacuuming of potato store
17S T O R E m a n a g E R S rsquo g U I D E
StorEHYGIEnE
Post-storagecleaning
bullStore-cleaningshouldbeundertakenannuallyInboxstoresthisisbestcarriedoutimmediatelyafterthelastcrophasbeenremovedsocleanedboxescanbereturnedtostore
bullInayearfollowingcropinfectionbysilverscurforskinspotextrarigorouscleaningshouldbecarriedout
bullVacuumdirtanddebrisfromfloorsledgesbeamsandotherhorizontalsurfaces
bullWhereinsulationisdamagedorisroughandcollectsdustrepairandvacuum
bullOnlypowerhoseifinsulationismoisture-proof
Cleaningboxes
bullEnsurethatbox-tippersongradinglinesaredesignedtodischargethetotalboxcontentstogetridofmajorcontamination
bullUsepowerhosetocleanboxes
bullWherecleaningboxesisroutineconsidersettingupaconveyor-basedautomaticwashingsystem
bullPower-washboxesforhighhealthcrops
bullWherepossiblereturncleanedboxestostoreorkeepundercoverasthiscanextendboxlifeby70
Whentousedisinfectants
Forhighhealthseedcropsdisinfectantsmaybebeneficialespeciallyafteracontaminatedcropinthepreviousyear
bullUsedisinfectantmistfogorsprayaftervacuumingstore
bullSpraydisinfectboxeswhichhelddiseasedcropout-gradesorlsquobrockrsquo
bullFollowinggradingofdiseasedpotatoespower-washgradinglinethenspraywithdisinfectantwheregradinghighhealthcrops
bullAlwaysuseapprovedproductsandseekspecialistadvice
notesomedisinfectantsmaydamagestoreinsulationandelectricalfittingsndashconsulttheproductlabelbeforeuse
dailycleaning
bullVacuumthefloorparticularlyforkliftroutesandundergradersatleastonceaday
Gradinginstore
GradinginstoreislikelytoincreasetheamountofcontaminateddustinthestoreandthelikelihoodofambientairenteringthroughopendoorsDustprovidesdiseaseinoculumwhileambientairmaycausecondensationparticularlyonthetopsurfaceofboxesorpile
bullIdeallygradeinseparatebuildingwithaplasticstripdoorbetweenthestoreandgradingarea
bullIfgradinginstoreisunavoidableenclosepickersinwarmedcabinandfitadustcontrolsystemtotheline
bullFitdewpointtemperaturemonitortowarnofcondensationrisks
ACTION POINTS
LeavingboxesoutsidewillallowlighttokillviablesporesBoxesshouldnotbestackedmorethanfourboxeshighforsafetyandifstackedinpairsasmallgapbetweenrowswillallownatural(ultraviolet)lighttoreachonesideofeveryboxHoweveroutsidestackingcanreduceboxlifebyupto40
CleaningandenergyefficiencyMaintainingfansventilationandrefrigerationequipmentinacleanconditionwillhelpprolongtheirworkinglifeand
improvetheirworkingefficiencyEnsurethattemperatureandhumidityprobesarekeptcleanandinspectlouvresevaporatorsandcondensersIfnecessarycleanbyvacuumingorpowerwashingIfwashingtakecarearoundelectricalandmovingsystemsandensurethatanyresultingiceisremovedbydefrosting
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
17S T O R E m a n a g E R S rsquo g U I D E
StorEHYGIEnE
Post-storagecleaning
bullStore-cleaningshouldbeundertakenannuallyInboxstoresthisisbestcarriedoutimmediatelyafterthelastcrophasbeenremovedsocleanedboxescanbereturnedtostore
bullInayearfollowingcropinfectionbysilverscurforskinspotextrarigorouscleaningshouldbecarriedout
bullVacuumdirtanddebrisfromfloorsledgesbeamsandotherhorizontalsurfaces
bullWhereinsulationisdamagedorisroughandcollectsdustrepairandvacuum
bullOnlypowerhoseifinsulationismoisture-proof
Cleaningboxes
bullEnsurethatbox-tippersongradinglinesaredesignedtodischargethetotalboxcontentstogetridofmajorcontamination
bullUsepowerhosetocleanboxes
bullWherecleaningboxesisroutineconsidersettingupaconveyor-basedautomaticwashingsystem
bullPower-washboxesforhighhealthcrops
bullWherepossiblereturncleanedboxestostoreorkeepundercoverasthiscanextendboxlifeby70
Whentousedisinfectants
Forhighhealthseedcropsdisinfectantsmaybebeneficialespeciallyafteracontaminatedcropinthepreviousyear
bullUsedisinfectantmistfogorsprayaftervacuumingstore
bullSpraydisinfectboxeswhichhelddiseasedcropout-gradesorlsquobrockrsquo
bullFollowinggradingofdiseasedpotatoespower-washgradinglinethenspraywithdisinfectantwheregradinghighhealthcrops
bullAlwaysuseapprovedproductsandseekspecialistadvice
notesomedisinfectantsmaydamagestoreinsulationandelectricalfittingsndashconsulttheproductlabelbeforeuse
dailycleaning
bullVacuumthefloorparticularlyforkliftroutesandundergradersatleastonceaday
Gradinginstore
GradinginstoreislikelytoincreasetheamountofcontaminateddustinthestoreandthelikelihoodofambientairenteringthroughopendoorsDustprovidesdiseaseinoculumwhileambientairmaycausecondensationparticularlyonthetopsurfaceofboxesorpile
bullIdeallygradeinseparatebuildingwithaplasticstripdoorbetweenthestoreandgradingarea
bullIfgradinginstoreisunavoidableenclosepickersinwarmedcabinandfitadustcontrolsystemtotheline
bullFitdewpointtemperaturemonitortowarnofcondensationrisks
ACTION POINTS
LeavingboxesoutsidewillallowlighttokillviablesporesBoxesshouldnotbestackedmorethanfourboxeshighforsafetyandifstackedinpairsasmallgapbetweenrowswillallownatural(ultraviolet)lighttoreachonesideofeveryboxHoweveroutsidestackingcanreduceboxlifebyupto40
CleaningandenergyefficiencyMaintainingfansventilationandrefrigerationequipmentinacleanconditionwillhelpprolongtheirworkinglifeand
improvetheirworkingefficiencyEnsurethattemperatureandhumidityprobesarekeptcleanandinspectlouvresevaporatorsandcondensersIfnecessarycleanbyvacuumingorpowerwashingIfwashingtakecarearoundelectricalandmovingsystemsandensurethatanyresultingiceisremovedbydefrosting
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
18 S T O R E m a n a g E R S rsquo g U I D E
sensingtwopairsofsensorsmeasuringthesurfacelayerdifferentialshouldbelocatedbelowoverheadcoolingairjetsinspaceventilationsystemswhilebulkstoresshouldhavetwopairsofsensorsinthetopsurfacelayerswithoneortwosensors300mmoffthefloor(Figure63)IfcondensationoccursinthesidesofthestoreasensorhalfwayupthesideofthepilecanbeinstalledAlkathenetube(egwaterpipe)makesagoodsleeveinwhichtofitsensorsatlowlevelinabulkstore
ExternalsensorsAccurateexternalsensorsplacedtoavoidinterferencefromthesunreflectedheatetcareimportanttoensureambientair-coolingoperateswhensuitablecoolairisavailableA1degCerrorinanexternaltemperatureprobecouldsignificantlyreducetheamountofcoolingobtainedSuppliersshouldcalibrateexternalRHsensorsevery1-2years
6 Servicingandsensors
ServicingStoresshouldbecleanedandequipmentcheckedassoonafteremptyingaspossibleAnyfaultsdiscoveredcanthenbesortedingoodtimepriortoharvestEmptyboxescanbeputbackintostorebeforeharvest
RoutineservicingbyinstallersofrefrigerationcoolingandmonitoringequipmentwillensurereliableandefficientstoreoperationduringthewinterandprolongplantlifeRefrigerationequipmentinparticularistoocomplextobeservicedbynon-specialistpersonnelInadditionimpendingregulationswillsoonrequirerefrigerantleakagetobemonitoredtominimiseozonedepletionintheupperatmosphere
StorecleaningandinspectionAnannualinspectionofstorefabricandhardwarecanbecarriedoutatthesametimeasstorecleaningP2Lookforsignsofdamageandtakeactiontosealanygapsandrepairdefectiveequipment(Figure61)
InternalstoresensorsCondensationonpotatoesmayoccuriftherearetemperaturedifferentialswithinthecropP11Goodstoremanagementshouldthereforeensurecroptemperaturesareasuniformaspossiblesosensorsshouldbesufficientlyaccuratetomeasuredifferencesassmallas05degCRegularverificationagainstacalibratedprecisionthermometeratambienttemperatureandmeltingiceat0degC(Figure62)shouldbecarriedouttoensurethatanydifferentialsmeasuredarerealandnotduetosensorinaccuracyAlwaysreplacesensorswhichshowanysignofdamagetoeitherthecableorprobe
InbothboxandbulkstoressensorsshouldpreferablybelocatedinthetopandbottomofthestackwithmostlocatedinthetopofthecropandsomeatthebaseegFigure63andFigure64(boxstore)Foroptimal
Figure 61 Damaged insulation will need to be repaired
BaseBox
TopBox
Box temperature sensors Bulk store temperature sensors
70mm300mm
Optional sensor ifcondensation occurs at sides
70mm
Temperature sensor
70mm
300mm
300mm
300mm
Figure 63 Locating temperature sensors for measuring temperature differentials
Figure 62 Calibration of sensors using melting ice
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
19S T O R E m a n a g E R S rsquo g U I D E
Figure 64 Sensor placement in a box store
Servicing
bullEnsurestoresareservicedannually
bullPayparticularattentiontofactorswhichwillinfluencethestorersquosefficiencysuchasrefrigerationequipmentandlouvre-sealing
Sensors
bullFaultyormisplacedsensorswillaffectcropqualityasthestorewillnotruncorrectlyThismayresultinover-ventilationwhichwillincreaseweightlossorincorrectstoragetemperatureswhichwillaffectfrycolourorblemishdiseasecontrol
bullReplaceanydamagedsensorsorcablesandcalibrateannuallytoensureaccuracy
bullPlacesensorstoprovidecomprehensivefeedbackonstoreperformance
ACTION POINTS
SErVICInGampSEnSorS
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
131211
9 10 7 8 5 6 1 23 4
9 10
3
17
2
4
8
5
6
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
20 S T O R E m a n a g E R S rsquo g U I D E
7 Loadingthestore
Figure 71 Separation of delivery and return air using a curtain
LoadingthestoreshouldbeanactivitywhichisplannedwellinadvanceofharvestItisimportanttomatchcropsintermsoftheirqualitylikelystorageperiodsandmarketexpectationstothestorageavailablesothatmanagementiseffectiveandreturnsaremaximised
HarvestingCropsshouldbeharvestedasfreeaspossiblefromdamagesoilstonesandhaulmWithinanhourortwoofenteringstorethecropshouldbeventilatedtoremovesurfacemoisturefromtubersandfromanyremainingsoilIfpositiveventilationisavailableasinbulkstoresorletterboxstoresventilationwillpreventcondensationformingontubersincropsliftedindryconditionsTheairflowremovesthewarmairproducedbytherapidlyrespiringcropandwillreducethelikelihoodofthewarmup-currentcondensingonthecoolerpotatoesabove
SpeedofloadingTrytoloadstoreswithinaweekandabsolutemaximumof14daysThisensurespotatoescanbebroughtunderoptimalcontrolandreducestheneedtocompromiseonstoremanagementandultimatelycropqualityIfloadingwithinthistimeframeisnotnormallyachievableyoumaybenefitfromdividingyourstoreintotwosmallersectionsTemporarycurtainscanbeusedasacost-effectiveoptionforthis
CropsamplingFieldsamplingwillidentifyrotsblemishdiseaseorslugdamagewhilewarmstorage(gt20degC)ofsamplesbeforeharvestcanidentifypotentialrottingpriortoloadingCropswithrotsorloadswhichhavebeenrainedonshouldbekeptoutofthebulkpiletopreventspreadofrottingthroughoutthepileCropswith1-2rotsshould
besetasideideallyinboxesandpositivelyventilatedcontinuouslyfor4-6weeksuntiltherotsaremummifiedCropswithover2rotshouldbesoldimmediatelyforconsumptionorstockfeed
InitialstorageDuringstore-loadingthetemperatureofthecropalreadyinstoreshouldideallytrackthedaytimeaveragetemperatureofthecropinthegroundusuallybetween20ordmCdownto10ordmCovertheharvestingperiodThestoreshouldbeventilatedwhenevertheoutsideairiswithinplusmn40ordmCofthecroptemperaturetoensureallsurfacemoistureisremovedandcondensationisnotcausedIfdew-pointtemperature-sensingisavailableitcanbeusedinsteadoftemperaturetopreventcondensationwhenventilatingwithairwarmerthanthecropCropsshouldbequicklyblowndrytopreventdiseasedevelopmentastherelativelywarmtemperaturesduringthisperiodencouragediseasedevelopmentifcropsaremoist
damagepreventionAsatharvestmechanicaldamagewhenloadingshouldbekepttoanabsoluteminimumRotsandblemishdiseasesP4invadethroughwoundsandbrokenskinwhilebruisingcausesrejectionfrompremiummarketsTestingfordamageshouldberoutinesothatincreaseddamagecanbequicklyidentifiedStandardmethodsofdamageassessmentareavailablehot-boxingsamplesovernightwillhelptoshowanybruisingAswinging-headelevatorwillenablesystematicloadinginbulkstoreswhilstmostautomatedboxfillersaredesignedtominimisedropsintoboxes
StackingboxesBox-stackingarrangementiscrucialtoachievinguniformairdistributionandcroptemperaturesTherollingairmass
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
21S T O R E m a n a g E R S rsquo g U I D E
Circulateairquickly
bullStartventilatingthecropassoonaspracticableensuringanyuncoveredductsorshortcircuitsaresealedoffasmuchaspossibletoforceairthroughthepotatoes
bullToreducecondensationriskmakesurethatthetemperatureinthestoretracksthatofthecropcomingin
bullKeepdifferentialstobelow4degCatloadingandtighterastemperaturesarereduced
Installprobesassoonaspossible
bullPlacetemperatureprobesintothecropassoonaspossiblesothatthereisaccurateinformationavailableonthecropconditiononwhichtocontrolorbasedecisions
ACTION POINTS
LoAdInGtHEStorE
BoxpositioningThemajorityofboxesshouldbealignedwiththemainairflowAlsomakesuretherersquosenoughgap(600mmisideal)forairtofallintoattheendoftheblockThisensuresthatairgetsintothepalletslotsundertheboxesandisthendistributedeffectively
BoxstackingWhereverpossiblestacksshouldbeofuniformheightIflowerstacksmustbeused(ontheshoulderofthestoreforexample)watchoutforcondensationanduselocalisedventilationtocontrolit
Cross-stackingYouwillsometimesneedtoputboxesatrightanglestotheairflowwhencross-stackingtocompletethestorefillIfcross-stackedboxesaresolid-sidedmakesuregapsofmorethan50mmareleftbetweenalternatestackstoallowairtopassthrough
createdbytheventilationsystemalwaystakesthepathofleastresistancePalletopeningsshouldbealignedwiththisairflowtoforceventilatingairwithin400mmofthecentreofeveryboxtoensuredryingandtemperaturecontrolisachievedThedepositionofthermalfogsproutsuppressantP18isalsoreliantoneffectiveanduniformairdistribution
WithlsquooverheadthrowrsquoventilationpoorairdistributionoftenoccursinthebackcornersofthestoreOverheaddistributionfanswhichassisttherollofairwithinstorewillhelptoevencroptemperatureandminimisepotentialcondensationOthermeasuresmightincludeseparationofdeliveryandreturnair(Figure71)andorpreventionofshort-circuitingbacktothemainfanaroundthestoreperimeter
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
22 S T O R E m a n a g E R S rsquo g U I D E
AutomationAnautomatedcoolingsystemcanbethoughtofashavingthreethermostats(temperature-operatedswitches)connectedinseriestotheventilationfanThethermostatsmonitortemperaturesasbelow
ThefancanonlyruniftheswitchesofallthreethermostaticallyoperatedswitchesareclosedorinthisexampletheanswertothefollowingthreequestionsisYES
Cropthermostat-croptemperature(set-pointrequired)ndashisthecroptoowarm
Differentialthermostat-temperaturedifferencebetweenthecropandoutsideThisthermostatmeasurestheconditionoftheairavailableinrelationtothecrop-istheoutsideaircoldenoughtocoolthecropeffectively
Frostthermostat-outsidetemperature(lowlimitprotection)ndashistheambientairfreefromfrost
efficientdryingthereisamovetohigherratesofupto004m3stwheretheairflowremovesheatmorerapidlywithlessweightloss
Theintroductionofinverters(alsoknownasvariablefrequencydrivesorvariablespeeddrives)thatenablefanspeedstobeadjustedhasofferedscopetolowerratesoncedryingandorpull-downiscompleteThiscanprovidesignificantsavingsinrunningcostsforexamplereducingafanto80ofitsfullspeedreducestheenergyconsumptionbyaround50P15ItisalsoausefulwaytocirculateCIPCsproutsuppressantP18
HoweverreducingairspeedstoomuchcanbedetrimentalsincethereisanattendantlossofpressureFanrunningtimesanddehydrationwillalsobeincreasedandresponsetimesreducedIfairisbeingdeliveredaspartofarefrigerationsystemP13icingupwilloccurifsufficientheatisnotremovedontheevaporatorUseofhumidificationcapacitycontrolonfridgesetcwilladdresssomeoftheseissuesbutspecialistadvicemustalwaysbesought
Ventilationratesforboxstoresaretypicallydesignedtobe002m3stInspace-ventilatedstoresthisairflowprovidessufficientairmovementaroundtheboxestodryandcoolboxesSincetheairisnotforcedthroughtheboxesheattransferispartlybynaturalconvectionbetweenboxesandthesurroundingairandpartlybytheturbulentairflowcreatedbythecoolairjetspassingoverthetopoftheboxesandthroughtheirpalletaperturesThisrateofairflowisprimarily
8 Ventilation
VentilationisacriticalprocessinstorageasthemovementofairthroughthepotatoesistheprimarymeansofregulatingthecropconditionbydryingcoolingheatinghumidifyingoraddingchemicaltreatmentsSpecificstrategiesareneededforkeyprocessessuchasdryingandinitialpull-downtoholdingtemperatureandfortheuseofrefrigerationwhicharediscussedinthefollowingsectionsManypotatostoreshoweverstillemployambientaircoolingwhichusesexternal(ambient)airwhensuitabletocoolthecrop(Figure81)Becauseambientairdoesnotneedtobemechanicallycooledrunningcostsareaboutaquarterthoseofrefrigeratedcooling
AirmixingIfamixingsystemisfitted(Figure82)theminimumallowedductairtemperaturecanberegulatedinrelationtothecroptemperatureInspellsofcoldweathertheinletlouvrewillbepartiallyshutandtherecirculationlouvrewillpartiallyopencausingtheincomingairtoblendwiththewarmerexhaustairfromthecropThisproducesventilationairwhichwillnotreducethetemperaturetoomuch(eginaprocessingcrop)norcreatetoolargeadifferential(typicallylt4degC)inthepile
VentilationratesInbulkstoresvirtuallyalltheairthatleavesthefanwillpassthroughthecropTraditionally002m3sthasbeentherecommendedventilationrateforbulkstoresinGreatBritainbutwithsomequalityparametersincreasinglydependenton
Fan
Power
Crop thermostat
Crop sensors
Frostthermostat
Differentialthermostat
Ambientair sensors
3
2
1
Figure 81 Basic ambient air-cooling system
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
23S T O R E m a n a g E R S rsquo g U I D E
2˚C
5˚C
5˚C
Fan
Louvres
Duct sensor
Airflow
8˚C
toaiddistributionratherthanthatrequiredtoremovethetransferredheat
PositiveventilationToachievemorerapiddryingandcoolingsystemsofpositiveventilationP9maybeusedTheseareespeciallysuitedtodensely-packedsoil-contaminatedpotatoesandearly-liftedcropsHoweverpositiveventilationincludingsuctionwallsystemsisalsoavaluabletoolfordryingpotatoesmaintainingclosetemperaturecontrolandapplicationofsproutsuppressant
CoolingSincecoolinginspace-ventilatedstoresisfromabovetheboxandbelowwiththegreatestairflowbeingoverthetopoftheupperlayerofboxesspaceventilationencouragestheundesirabletemperatureprofilewithintheboxndashcoolatthesurfaceandwarminthecentrendashwhichisliableto
Automateventilationsystems
AircanonlybeusedeffectivelyinstoresifitisoftherightqualityforthejobitisrequiredtodoToensurethatthisisalwaysthecasetherehastobecontroloftheairdeliveryandthiscanonlyrealisticallybeachievedthroughautomation
bullFitanautomaticcontrolsystemtoallstoresconsiderupgradinganyoldersystems
bullAvoiduseofmanualsystemswhicharepronetohumanerrorandvariationsinclimatewhichcanquicklyandirrevocablyjeopardisecropquality
Bepositive
Positiveventilationwheretheairhastopassthroughthepotatopileorboxisthebestwaytogeteffectiveresultsinstorage
bullUsepositiveventilationsystemswherepossibleespeciallyfordrying
Matchsupplytodemand
bullConsiderinstallingcontrols(eginverters)tosupplyvariableamountsofairtomatchthedemandsofthestoreTheycanofferpotentialenergysavingstoondashforexampleveryhighventilationratesusedfordryingarenotusuallyrequiredintheholdingperiodObtainspecialistadvicebeforeretro-fittingtoexistingsystems
ACTION POINTS
VEntILAtIon
Figure 82 Mixing or blending of air
resultinsurfacecondensationwhenventilationstopsThereasonthisformofventilationissopopularisthatitislowincostutilisestheotherwiseunusablestoreheadspaceasadistributionductandworksinpracticesolongassomeprovisosareadheredtoThecoolingairshouldbenocoolerthan4degCbelowthetemperatureofthecroptominimisethetemperatureprofileintheboxP10Theotherrequirementisthattheairdistributionshouldbeasuniformaspossibleoverthewholeareaofthestackofboxes
Whencoolingspace-ventilatedstoresthestorebecomesfloodedwithcoolairTheairwithintheboxesisnowwarmerthanthesurroundingairsotherateofconvectionventilationincreasesHoweverthisprocessismuchslowerthaninpositiveventilationsystemssocoolingtakeslongerAsambientcoolingreliesontakingadvantageofcoolairavailabilitypositiveventilationwillkeepambientstorescoolerthanthosewithspaceventilationIntrialsthebenefitofpositiveventilationwasc15degCcoolerstorageoverawinterperiod
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
24 S T O R E m a n a g E R S rsquo g U I D E
rateofdryingIfaboxorpileofpotatoesispositivelyventilatedfrombottomtotopthebaselayerdriesfirstAdryingfrontformsafewcentimetresdeepoverwhichtheairbecomessaturatedwhichmeansitcannottakeupanymoremoistureThislsquodryingfrontrsquothenprogressesveryslowlyupthroughthecropanddependingontheairflowratemaytakebetweentwodaysandaweektotravelthroughthepotatoesBelowthefrontthecropisdryaboveitisstillwetThesaturatedairleavingthefrontpassesupthroughthewetpotatoeshigherupdoingverylittledryingasitrisessomosteffectivedryingactuallyoccursinthisnarrowdryingfront
therateofdryingdependsonbullAirflowratewhichinturndependsonfanoutputandair
leakagefromthesystem
bullTemperatureoftheairwhichaffectsitswater-holdingcapability
bullRelativehumidityoftheairwhichdictatestheamountofwatertheaircantakeup
bullAmountofmoisturepresentonthepotatoesandintheadheringsoil
9 drying
FreemoistureWhenacropisbroughtintostoremoistureintheadheringsoilcomeswithitAirsurroundingafreewatersurfacehasarelativehumidity(RH)of100ThisfreemoisturemustbeevaporatedoffiftheRHoftheairistoreducetothelevelassociatedwithdrypotatoesndashabout96WhilethisdifferenceinRHwouldappearsmallitisthekeytohavingadryfresh-smellingstorewhereeverytuberhasadryskinratherthanadankonedrippingwithmoisture
ImmaturecropsharvestedfromdrysoilswillbecomewetthroughcondensationifthereisinsufficientrateofpositiveventilationtoremovethehighrespirationheatproducedDryingwillthenbenecessarytoremovethiscondensedmoisture
Water-holdingcapacityofairWarmaircanholdmoremoisturethancoldairAcubicmetreofaircanhold175gofwaterat20ordmCbutonly95gat10ordmCandjust64gat4ordmCThedryingofcropsinwarmweatherinSeptemberorearlyOctoberisthereforemuchquickerthanifattemptingtodrycropsincoldweatherinlateNovemberThehighheatoutputfromthecropoverthefirstfewdaysafterliftingwillalsowarmthedryingairflowmakingdryingevenfasterduringthisperiod
Figure 91 Ventilation through lateral ducts in a bulk store
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
25S T O R E m a n a g E R S rsquo g U I D E
Positiveventilation
bullDryingismosteffectiveifventilationispositivendashwheretheairdeliveredhastotravelthroughtheboxorpileofpotatoes
bullInbulkstores(Figure91)virtuallyalloftheairflowsthroughthecropwhereasinpositivelyventilatedboxstoragesystemsatleast50oftheairtypicallyescapesthroughgapsbetweentheboxes
bullLetterboxsystems(Figure92)arelimitedto8-10boxesdeepforeffectivedryingSuctionwallsystemsaremoresuitedtostoreswithmorethan10boxesperrow
Airflowratesforeffectivedrying
bullUsethehighestairflowrateavailablefordryingBatchsystemsareverywellsuitedtodryingasairflowcanbeconcentratedonasmalltonnageatatime
bullBulkstoresrequireaminimumof002m3strisingto004m3stforearlyliftedcrop
bullBoxstoresneedupto008m3sttoallowforairleakage
Condensationriskwhendrying
Thehumidexhaustairfromacropbeingdriedwillbenear100RHIfthisaircomesintocontactwithcoldpotatoesitwillcondense
bullEnsurecropalreadyinstoreisatsametemperatureascropbeingliftedtopreventwarmhumidairfromonestackcondensingonthosealreadydried
ACTION POINTS
drYInG
Drywarmambientaircanstillcausewettingifitcomesintocontactwithcoolerpotatoes
bullUseexternalairfordryingaslongasitisplusmn4degCofcroptemperatureorwheredew-pointcontroloffansisavailable
Freemoistureonthecroporadheringsoilwillhumidifyairmovingthroughthecropbyconvectionmakingcondensationonotherpartsofthestoredcrophighlylikely
bullEnsurethereisairmovementthroughoraroundthenewly-liftedcropwithintwohoursofthecropenteringthestore
optimisingdryinginspace-ventilatedstores
AirwillalwaystrytotakethepathofleastresistanceBoxesshouldbestackedsothataircannotbypassboxesUsecanbemadeofpalletaperturestoensuredryingairflowisalwayswithin400mmofeverypotatoinstoreShortcircuitingofaircanbeaprobleminpart-loadedstoresreducingeffectivenessofdrying
bullInboxstoresstackboxesacrossthestoresothatairflowhastoflowthroughpalletaperturesBlockreturnairpathsaroundthestoreperimetertoforcemoreairthroughthecrop
bullWherevarietieshavetobestoredinseparaterowsforaccessstartrowsincentreofthestoreanduseemptyboxesorcurtainstoblockanyeasyreturnpathfortheventilatingair
Figure 92 Traditional air distribution letterbox duct
Foam
Bulk boxes
Foam
Foam
Letterbox duct
Letterbox openings
Fan
Fan
Air
Air
Air
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
26 S T O R E m a n a g E R S rsquo g U I D E
andconditionswhereskinspotorgangrenedevelopmentislikely(eglate-harvestedbadlydamagedKingEdward)whereascuringcouldbeomittedwheremarketsdemandlowlevelsofsilverscurforblackdotandpull-downcouldcommenceonloading
Figure102illustratesthatdevelopmentoflsquolowtemperaturersquodiseaseslikeskinspotismorelikelywherecuringisomittedThosediseaseswhichfavourhighertemperatureslikesilverscurfandblackdotcantakeadvantageofconditionsassociatedwithtraditionalcuringregimesFigure102alsoshowsthattheinitialeffectcanpersistintolong-termstorage
drycuringDrycuringwherecropsareventilatedwithsuitableambientairimmediatelyonenteringstoreallowsdryingheatremovalandwoundhealingtooccursimultaneouslyStudieshaveshowndiseasedevelopmenttobemarkedlyslowedbydry-curingtechniquescomparedwithleavingthecroptoventilatenaturallyAscoolingisnotdesiredduringwoundhealingventilationcontrolisnormallysettomanualOnmanualtheautomaticcontrolboxisswitchedoutofcircuitandonlythefrostthermostatifwiredcorrectlywillstopventilationshouldambienttemperaturefallbelowitssetpoint
TheaimofventilationwhendrycuringistodrythecropandkeepitdrySelectionofsuitablequalityairisessentialandshortcondensationeventscanundothebenefitfromdrycuringasre-wettingcaninitiatediseaseslikesilverscurf
10 Woundhealingandpull-down
WoundsasroutestoinfectionWoundsallowfungiandbacteriatodevelopinthefleshofthetuberSuberinformationbetweenandbelowdamagedsurfacecellsprovidesaninitialbarriertodiseaseentryandnewcellsformsoonafterintoamoreimpenetrablebarrierRateofwoundhealingisprimarilyinfluencedbytemperature(Table101)andisfasterinrecentlyharvestedcropscomparedwithphysiologicallyoldcropssuchasthosegradedinthespringHumidityplayslittlepartinspeedingwoundhealing
Therateofmoisturelossfromfreshwoundsisoftheorderof100timesthatfromundamagedskinandweightlossoverthefirstfewdaysisinevitableThefasterthewoundshealthelessthisweightlosswillbe
risk-basedapproachesDecisionsonwhethertocurecropsornotwilldependonthedesiredmarketandthepotentialfordiseasedevelopmentP4Forexamplealongdurationatarelativelyhightemperaturewillberequiredforvarieties
tuber Initial Periderm
temperature suberisation complete
(˚C) (days) (days)
lt5 7-14 21-42 10 4 7-14 20 1-2 3-6
Table 101 Wound healing rate in relation to tuber temperature
SBEU trials
Figure102 Effect of variety and curing strategy on development of different diseases
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
27S T O R E m a n a g E R S rsquo g U I D E
VentilationamprecirculationIfconditionsarenotsuitablefordrycuringwithambientairitisimportanttomaintainairmovementinthestoretoavoidtemperaturegradientsbecomingestablishedThiscanbeachievedbyregularrecirculation(usingauto-recirculationcontrolifrequired)especiallyatnightwhenthestoreisclosedandthereislessriskofdrawinginunsuitableexternalair
Pull-downAssoonaswoundhealingofthelastcroploadediscompletethecropshouldbebroughtdowntoitsrecommendedholdingtemperatureEarliercommencementofpull-downislikelytobeappropriateforsomemarketsasdiscussedaboveThetemperatureofthecoolingairshouldbekeptinabandbetween1-4degCbelowthecroptemperaturenocoolerInfridgestorescoolingratesshouldaverageoutatabout05degCday
WhilearelativelysmalldifferentialmayreducethecoolingratealargeronecancauseexcessivetemperaturedifferenceswithinboxesThiscanresultincondensationwhenwarmhumidairwithinthecentreoftheboxrisesandcondensesonthecooledsurfacetubersunlesspositiveventilationisused
decideoncuringapproach
bullConsultriskassessmentadvice
bullAssessandcomparemarkettolerancesandrisksfordevelopmentofdamage-relateddiseases(skinspotgangrenedryrot)andblemishes(blackdotandsilverscurf)Ingeneralcurefortheformerandpull-downforthelatterP4
Pull-down
bullPulldownwillbemosteffectiveifairispassedthroughthepotatoessoavoidshort-circuitingandmakesurethatpalletslotsarenotblockedP8
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
Curendashifnecessary
bullWithambientsystemsensureanyoutsideairusedtoventilatethecropiswithin4degCofthecroptemperaturetoavoidcondensation
bullForcropsharvestedatlowtemperaturesdonotventilatewithwarmerambientairunlessyouknowthereisnoriskofcondensationP11Appendix4
bullForcropswithrottingorathighriskofitdevelopingomitwoundhealingreducetemperaturequicklyandplanshorttermstorageonly
Considerusingacontrollerwithwound-healingcondensationriskmonitoring
bullSetrecirculationtobeactivatedwhenambientairdew-pointtemperatureis1degCbelowcroptemperature(egifcropisat14degCrecirculationwillstartwhendewpointtemperaturereaches13degC)
bullSetminimumventilationtemperatureto4degCbelowcroptemperature
ACTION POINTS
WoundHEALInGampPuLL-doWn
Figure 103 Effect of curing strategy on subsequent development of black dot
SBEU trials
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
28 S T O R E m a n a g E R S rsquo g U I D E
Figure 112 Ventilation-induced condensation
bullAirtemperatureandrelativehumidityarerelatedIfthetemperatureofairrisesthemoisture-carryingcapacityincreasesandtheRHwilldropConverselyifthetemperatureofairfallstheRHwillincrease
bullInpotatostoragewarmmoisture-ladenaircomingintocontactwithcoolerpotatoesisacondensationriskastheairmaybecooledsufficientlyforittobecomesaturatedwithmoisture(100RH)Thetemperatureatwhichthisisreachediscalledthedew-pointtemperatureBelowthistemperatureanywatertheaircannolongercarrywillbedepositedonthepotatoesascondensation
bullInthesamewayinmeteorologywherewarmandcoolairmassesmeetintheskythismoisturefallsasrainAndwhenashowerisruninabathroomthewarmmoistairwillcondenseoncoolsurfacessuchasthewindow(Figure111)
bullCoolaircomingintocontactwithwarmerpotatoesisnotacondensationrisk
Condensationonthecropcanoccurinanumberofsituationsbutwillonlydosodirectlyif
bulltheairsurroundingthepotatoesiswarmerthanthepotatoesand
bullthepotatoesrsquosurfacetemperatureisbelowthedew-pointtemperatureoftheair
Asageneralruleatemperaturedifferenceof4degCormorebetweenthewarmairandthecoolercropwillcausecondensationButinsomesituations(egatcoldtemperatures)thisdifferencemightonlyneedtobeaslittleas1degCforcondensationtooccur
notethatthelowerthetubersurfacetemperaturecomparedwiththeairrsquosdew-pointtemperaturethemoremoisturewillbedeposited
11 Condensationonthecrop
CondensationisamajorconcerninpotatostorageInasealedstoreoverjustamatterofhourspotatoescannaturallycreateanenvironmentwithahighrelativehumidity(RH)of90orhigherAtsuchahighRHcondensationcanoccuronthecrop(orroofP12)ifthesurfaceisonlymarginallycolderthantheairCondensedmoistureispurewaterhighlyavailabletomicro-organismsresidingonthetuberskinorinwoundslenticelsorsproutbudsAcondensationperiodofjustanhourmayallowblemishdiseasedevelopmentorrottingtobegin
SomebasicfactsaboutcondensationbullWarmaircancarrymoremoisturevapourthancoolair
At20degCaircancarry175gm3butat4degCitcanonlyholdamaximumof64gm3
bullRelativehumidityisawayofexpressingtheamountofmoistureinagivenvolumeofairinrelationtoitsmaximummoisture-carryingcapabilitySoif1m3ofairat4degCisat50RHitcontains50or32gofthemaximum64gm3thataircanhold
Figure 111 Condensation will occur when warm moisture-laden air comes into contact with cold surfaces
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
29S T O R E m a n a g E R S rsquo g U I D E
Storeloading
bullMinimisetemperaturedifferentialsbykeepingthestoretemperatureatthatofthepotatoesbeingloadedintostore
Placementofsensors
IfatallpossibleusetemperaturesensorstomonitordifferentialswithinthecropP9
bullInbulkstoresputsensors100mmand300mmdownfromthetopsurface
-Topsurface(100mm)sensorshouldbenomorethan05degCcoolerthansensor300mmdown
bullInboxstoresmonitorbasetotopboxdifferenceupthestack
-Keepthedifferencebetweenboxesbelow4degCduringloadingandwoundhealingandbelow15degConcethecropisdowntoholdingtemperature
-Ifpossibleinspace-ventilatedstoresplacesensorsintwotopboxes70mmand300mmdownfromthesurfaceKeepdifferencesin-boxbelow05degC
dryingorcoolingthecrop
bullOnlyintroduceairintothestoreifthetemperaturedifferencebetweentheairandthepotatoesislessthan4degC
bullOnlyventilatewithairwarmerthanthecropifthecroptemperatureisabovetheairrsquosdew-pointtemperature
Minimisingtemperaturedifferentialventilatingusingoutsideair
bullWhereoutsideairissuitable(iebetween1-4degCbelowcroptemperature)ventilationratherthanrecirculationcanbeusedtoevenouttemperaturedifferentialsinthecrop
bullSetminimuminlettemperatureat4degCbelowcroptemperature
Minimisingtemperaturedifferentialbyairrecirculation
bullOnlyrecirculatewhentemperaturesensorsindicateabuildupofdifferentialsandif
-Headspaceairisbelowtemperatureofpotatoesatbaseofpileor
-Basepotatotemperatureisnotbelowheadspacedew-point
Cropwarming
bullThedew-pointtemperatureofthewarmingairmustbeabovethecroptemperature
bullWherepossiblewarmcropsinthecoldstorewheretheaboveconditionexistsandventilationortherefrigerationsystemwillremovetheheatthatdoesnotenterthecrop
bullWhenreturningwarmgradedmaterialtothecoldstore(egafterseedgrading)
-Pre-coolsothatitislt4degCabovecropinstore
-Positivelyventilateuntilcropisdowntotemperature
Sprouting
bullIfsproutingoccurscheckitisnotaresultofcondensation
Airleakage
bullPreventwarmairleakingintotheheadspacebysealinggapsinthestructureandkeepingstoredoorsclosedespeciallyinwarmhumidweatherP 2
ACTION POINTS
toMInIMISECondEnSAtIonontHECroP
Whencondensationcanoccur
bullAllowingwarmambientairtodriftintoastoreofcoolerpotatoessuchasthroughanopendoorcanresultinthecropnearthedoorbecomingwet
bullPuttingwarmpotatoesintoastorewithcoolercropalreadyinitIfthetemperaturedifferenceisnotmanagedthereisariskofwarmairrisingfromthewarmcropandcondensingonthecoolerpotatoes
bullRecirculatingwarmmoisture-ladenaircomingoutofthetopofastackbackintothecoolerbaseofthepilecarriestheriskofcreatingcondensationinthelowerlevelsofthestack
bullAfterventilatingthetopofaboxstorewithcoldairthefansgooffallowingwarmairtorisethroughthecropbyconvectionThiswarmairhitsthecoolerlayerofcropatthetopofthestoreandcondensesonthe(undersideof)thetubers(Figure112)
bullDuringperiodswithoutventilationwarmairrisesbyconvectionfromthewarmestpart(usuallythecentre)ofastoreandisreplacedbycoolerairfromthesidesofthestoreThisinturnisreplacedbythewarmairfromthecropwhichthencondensesinthecoolercropalongtheshoulders
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
30 S T O R E m a n a g E R S rsquo g U I D E
Figure 122 Effect of transient temperature changes in external climate on well sealed stores
12 Structuralcondensation
risktocropCondensationformingonthebuildingstructurecanleadtoproblemsinthecropOntheroofitformsontheundersiderunsdowntothepurlinsandthendripsinlinesontothepotatoesbelowThewetpotatoescanstartrottingorskin-surfacediseasemaydevelopCondensationonwallsisonlyariskinbulkstoreswherethemoisturecanaccumulateonthefloorwettingthetubersatfloorlevel
HowcondensationoccursCondensationonthestructurewilloccuriftheinternalsurfacetemperaturefallsbelowthedew-pointtemperatureoftheairnexttothesurfaceThismayoccurduetooneormoreofthereasonsbelow
bullTheinsulationisinadequateorhasfailedbecauseitiswet
bullAirmovementacrosstheroofinternalsurfaceisinsufficientallowinglocalisedhighRHattheroofsurface
bullAcoldspellofweathercausesheatbutnotvapourtoescapefromthestore
bullInternalstoreatmosphereisatornear100RH
WellsealedstoresIfasealedstoreisat8degCRH92withanexternaltemperatureof8degCasteadystatesituationwillresultwhereheatneitherleavesnorentersthestore(Figure122)Iftheambienttemperaturerisesto12degCheatwillenterthestoreraisingthestoreairtemperaturereducing
Figure 121 Roof recirculation fans can alleviate problems with structuralcondensation
itsRHHeatcanpassthroughtheinsulationbutvapouristrappedinstoreIftheexternalairreducesto3degCheatwillleavethestorethestoreairtemperaturewilldropanditsRHwillriseto100CondensationwilloccuronthecoldestsurfaceswithinthestoreusuallytheroofbutitmayalsooccuroncoldsectionsofthecropWhilethisisatransientphenomenonitcaninitiatediseaseandrottinginthecropThisiscalledinterstitialcondensation
CondensationcanalsoformwithinthestructureandbehindinsulationIfmoisturepenetratesintothestructureboardscanbecomephysicallydetachedandinsulationvaluesgreatlyreducedP2
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
31S T O R E m a n a g E R S rsquo g U I D E
PreventionofcondensationStructuralcondensationwillbeminimisedby
bullGoodlowconductivityinsulation(fridgestoresndashU-value=03Wm2degCforroof038Wm2degCwallsambientstoresndash04Wm2degCforroof045Wm2degCforwalls)
bullRecirculatingairintheheadspaceusingfans(Figure122)topreventtemperaturedifferentialsinlayersofstillairundertheinsulationwhichcanleadtolocalisedcoolingandincreasedRHFansshouldbeinstalledsothattheairmovementcreatesahorizontalrotationwithintheheadspace
Checkforcondensation
bullDuringcoldweather(gt6degCbelowthestoretemperature)lookcarefullyforsignsofstructuralcondensationonegundersideofroof
bullCheckforsignsofdrippingfrominsulationjointsorsaggingroofinsulationcausedbyinterstitialcondensationSeekspecialistassistancetorectifyanyproblems
Insulation
bullCheckthethicknessofinsulation(usuallyatleast75mmthickforrefrigeratedstoresand50mmforambientcooledstores)Whereitfallsbelowthesemeasurementsconsiderincreasingitsthickness
bullReplaceanydamagedinsulation
roof-spaceheating
Betterinsulationandairmovementintheroofvoidreducestructuralcondensationbutroof-spaceheatingistheonlywaytopreventit
bullFitroof-spaceheatinginstoresthatarepronetostructuralcondensationduringcoldweatherespeciallythoseheldathigherstoragetemperaturesforprocessing
bullAutomatesystemstostartwhentheheadspaceairtemperaturefallsc1degCbelowcrop(surface)temperatureAdjustexactsettingstosuitthestoreinquestion
bullIdeallyuseacontrollerwhichcanbothoperateandmonitorroof-spaceheatingindependently
bullWhereanexistingcontrolsystemcannotcontrolroof-spaceheatinguseaseparateelectricsensorwithtemperaturedifferentialcontroltobringonheaters
bullFitaninterlocktoensureanyoverheadcoolingdoesnotswitchtheroof-spaceheatingon
ACTION POINTS
toMInIMISEStruCturALCondEnSAtIon
bullInstallingroof-spaceheaterstoreplaceheatlossduringcoldspellsofweatherThesecanbeusedinconjunctionwithrooffansandorpolythenedistributionductsRoof-spaceheatingcanbeprovidedbyelectricheatingcablesuspendedfromtherooforelectricheaterelementsfittedwithinheadspaceaircirculationfansHeatoutputshouldbec10Wm2ofstorefloorarea
bullTreatingpurlinsetcwithcoatingproductstopreventcondensationformingonthemFixingnailscanformacoldbridgewhichcanalsoleadtolocaliseddrippingButthisiseasilyremediedbycappingthefixingswithapieceofboardinsulation
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
32 S T O R E m a n a g E R S rsquo g U I D E
RefrigeratedstorageoffersthescopeforcloseenvironmentalcontrolAcombinationofambientair-coolingandrefrigerationcanreducetheenergyrequiredfordryingandcoolingwhenambientconditionsallowwhileretainingtheabilitytocontroltemperaturesinstorewhenwarmwintertemperaturesprevailWithlongtermstorageaccountingforupto100kWhofenergyusepertonneensuringthatsystemsworkefficientlywillnotonlypreservecropqualitybuthelpmanageenergycosts
ArefrigerationsystemconsistsoftwoheatexchangerstheevaporatororcoolingcoilsinsidethebuildingandthecondenseroutsideTheseareconnectedbyacircuitcontainingaliquidgasrefrigerantHeatfromthestoreispumpedoutofthestoreintherefrigeranttothecondenseroutsidebyacompressorCondensersoftenhavebanksofmultiplefansfittedfordissipationofheatwhichareswitchedonsequentiallyaccordingtodemandFittinginverters(variablespeeddrives)canbeagoodwaytoreduceenergyconsumptiononmultiplefancondensersetsP15
AirfromthestorepassesovertheevaporatorandiscooledaccordingtothesizeofthecompressorThiscooledairisblownoutofthefridgetorecirculatearoundthestoreThetemperaturedifferencebetweentheairgoingintothefridge(theair-on)andthecooledaircomingout(air-off)reducesasthestoretemperaturefalls(Table132)butshouldnotexceed25-3degC
MaintenanceandfaultsRefrigerationsystemsarecomplexandshouldbeservicedannuallybythesupplierHoweveroperatorscanhelpensuretheequipmentoperatesefficientlybycarryingoutthefollowingsimplechecksbeforeuse
bullCompressorcrankcaseoilheaterisswitchedon24hoursbeforestarting
bullCondensercoilsoutsidearefreefromleavesanddirt
bullRefrigerantisdryandclearofairbubbles(usethesightglassorothermonitoringdevice)
bullCompressorisoperatingwhentherecirculationfansareoperating
bullCheckthecalibrationoftemperatureandhumiditysensors
RegularchecksofthehighandlowrefrigerantpressureswitchesneedtobemadeduringoperationasthesecantripoutthecompressorFansmayoperatewhileinpracticenocoolingistakingplace
CombinedambientrefrigeratedsystemsIncoolingmodesimplecontrolsystemswilltendtofavourtheuseofrefrigerationoverambientair-coolingIndeedthesoleuseofrefrigerationtoachieveacontrolledpull-downisincreasinglycommoninstorageforpre-packingP11
AmbientsystemswilluselessenergyandhavelowerrunningcostscomparedwithintensiverefrigerationCombinedambientfridgesystemswillhaverunningcostssomewherebetweenthetwoMoresophisticatedcontrolsystemsallowdelaystobeinstalledforfridgeoperationwhicheitherallowcoolingtowaituntilnighttimelowtemperaturesareavailableorenablelowercostenergytariffstobeusedP17
defrostThetemperatureoftheevaporator(coolingcoils)isc6degClowerthanthecroptemperatureTheairflowingthroughtheevaporatoriscooledtoalevelbetweentheair-ontemperatureandtheevaporatortemperatureAtlowstoragetemperatures(lt25degC)condensateislikelytofreezeontheevaporatorcoilswhichwillrequireperiodicdefrosting(Figure133)Defrostisoftenonlyavailableasoff-cycle(iethesystemshutsdown)butitismoreefficientifdefrostcanbecarriedoutondemandavoidingunnecessarydowntimeorheatingofcoilswhichhavealreadybeenclearedofice
13 refrigeration
Figure 131 Refrigerated storage
Table 132 Typical air-onair-off values for refrigeration systems
Airfrom Airfrom Air-on crop outletduct air-off (air-on) (air-off) tempdiff
120˚C 90˚C 30˚C
80˚C 55˚C 25˚C
35˚C 15˚C 20˚C
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
33S T O R E m a n a g E R S rsquo g U I D E
Figure 133 Ice must be regularly cleared from cooling coils
TheneedfordefrostcanbeavoidedinmanypotatostoresprovidingtemperaturecontrolinthestoreisuniformStorageatc35degCshouldbesufficienttolimitthe
developmentofblemishdiseasesandpreventsproutinginallbutthemostprolificvarieties
Storeintegrity
RefrigerationcostscanbereducedifstoresarewellsealedOnlyonepreferablysmallopeningdoorshouldberequiredforwinteraccess
bullCarryoutastoreassessmentP1
bullCloseoffandsealanydoorsorlouvresnotrequiredforaccessorventilation
bullUsecontrollerwithpositivelouvre-closingactionservicesystemannually
Condensationriskduringrapidpull-down
Refrigeratedstoreshavelesscondensationriskinthesurfacelayersofboxstoresthanambientasthecoolingairisalwaysaround15-25degCcoolerthanthecropButtoorapidcoolingiegt07degCdayoftenaimedatlimitingdiseasedevelopmentmayresultintemperaturedifferentialswhichcouldleadtocondensationP12
bullAthighcoolingratesrefrigerateforfewerhoursperdayandrecirculateairwiththecompressoroffforotherperiods
bullIfcondensationisseenshortencoolingperiodsandrecirculatemore
ACTION POINTS
rEFrIGErAtIon
bullEnsureattemptstoslowtheonsetofdiseasedonotinadvertentlycausecondensationanddiseaseinitiation
usingafridgetodrypotatoes
WherepotatoesarewetafridgecanbeusedtodrythecropThecirculatingairinstoreabsorbsmoisturefromthecropandasthishumidairpassesthroughtheevaporatormoisturecondensesoutanddrainsaway
bullNotethatrapidremovalofmoisturebyevaporationalsocoolsthecropmore
bullUseaheatertocompensateforexcessevaporativecoolingmdashbutonlyinextremesituations
overridethermostatprotection
Asystemwithrefrigerationshouldalwaysbefittedwithback-upprotectionagainstexcesschillingintheeventofcontrollerfailure
bullFitanoverridethermostatwhichisindependentlywiredtoturnfridgeoff
CIPCuseinfridgestores
CirculatingCIPCthroughrefrigerationcoilscancausedamagetothecoilP18
bullBypassfridgecoilsifcirculatingCIPCfog
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
34 S T O R E m a n a g E R S rsquo g U I D E
HumidificationBysupplementingthemoisturecontentoftheairthroughhumidification(Figure141andFigure142)thereisscopetoincreaseitsRHandreducemoisturelossfromthecrop
Arangeofsystems(Table143)isavailableAdvantages
associatedwiththeuseofhumidificationinclude
bullReductioninpressurebruisingcompressiondamageatthebaseofabulkpile
bullImprovedturgorandtuberintegrity
bullEnhancedtemperaturecontrolduetoadiabaticcooling(seebelow)
bullRemovalofdiseasesporesfromstoreair(withcellhumidifiers)
14 Humidity
HumidityandmoisturelossPotatoeshaveahighwatercontent(over70)andinstoragelosemoistureovertimethroughevaporationtotheenvironmentaroundthemAt4degCtubersreachequilibrium(ietheyneitherlosenorgainmoisture)whenthesurroundingairisat98relativehumidity(RH)veryclosetosaturationAstheRHofairsurroundingstoredpotatoesfallswaterlossincreases
VentilatingapotatostorewilltosomeextentdehydratethecropAsairmovesthroughthepotatoesitpicksupheatthatlowersitsrelativehumidityWheretheskinofthetuberisnotintacteitherduetopoorskinsetorun-healedwoundsincreasedmoisturelosswilloccur
Therisksofdehydrationfromventilationcanbeminimisedby
bullHarvestingwithsetskinsndashthisisacriticalmeasuretominimisemoisturelossfromthetuber
bullOptimisingtheventilationtimethroughregulatingthequantityandtemperatureoftheairusedtoattaintherequiredstorageconditionThisisbestdoneusinganautomaticventilationcontrollerasthiswillonlybringonthefanswhenventilationisactuallyrequiredandtheairissuitableAsthepotatorsquosskinactsasaregulatortotheprocessofmoisturelossfromthetuberthelevelofmoisturelostwillbeproportionaltotheventilationtimeduringtheholdingperiod
Theeffectsofdehydrationcanalsobeexacerbatedbydeeppilestorage(gt4mdeep)whereitiscommontoseesomeevidenceofcompressiondamageincropsremovedfromlong-termstorageInseverecasescompressiondamagecanbeseenwithinboxeswheredepthsareseldommuchmorethan1m
Figure 141 Cell humidifier
Figure 142 Continuous recirculation of humidified air
Fan
Humidifier
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
35S T O R E m a n a g E R S rsquo g U I D E
Table143 Humidification systems
typedescription
Cellhumidifiers
Thesesystemsuseaspecialperforatedtreatedpapermembrane(cell)downwhichwateriscascadedtohumidifyairblownthroughthemembraneatrightanglestothewaterflowThecellhasaveryhighsurfaceareatooptimisetheuptakeofmoisture
Atomisersystems
UltrasonicatomisersusecompressedairtoshatterthewaterintoaveryfinemistDeliveryofthewatertotheairisthroughnozzle(s)whichareusuallyplacedwithintheventilationductofthestore
Spinningdiscs
Thismethodofhumidificationusesahigh-speedrotaryatomisertobreakthewatersuppliedtothediscintoafinemistthatthenentersthestorethroughtheventilationsystem
Benefitsdisadvantages
bullCanbefittedretrospectively
bullDonotrequireactivecontrolofhumidification
bullCanfilteroutsomediseasespores
bullCanbefittedretrospectively
bullSmallriskoffreewaterbeingcarriedintothecroprequiringclosemonitoringatalltimes
bulllsquoActiversquoorpulsedcontrolofhumidificationisneeded
AfurtherbenefitofhumidifyingisevaporativecoolingIfmoistureisevaporatedduringtheventilationprocessthishastheeffectofcoolingtheairatthesametimeThismeanssystemsusinghumidifiedaircanoperateattighteraircropdifferentialsasthedifferentialiswidenedasaresultofwaterevaporationThisisknownasadiabaticcoolingP8
Howeverahumidifiershouldonlybeusedinawellsealedbuildingwithacloseleveloftemperaturecontrol(rangelt05degC)Humidificationcannotbeexpectedtorectifymajordeficienciescausedbyincorrectventilationsystemsorpoorrefrigeration
Preventionofsurfacecondensation
Inhigh-humiditystoragecropscanbeaffectedbycondensationwhentheexternaltemperaturesuddenlydropsP1213
bullFitroofspaceheatingtoprovideautomatedcontrolofheadspacetemperature
Moistureloss
Ifmoisturelossisaproblemthecauseshouldbetracedandcureddirectlyifpossible
bullMeasurefanrunningtimes(moisturelossisproportionaltoventilationtime)
bullCheckforairleakage
bullCheckfridgeaironairofftemperature
Control
SinceitisdifficulttomeasureRHaccuratelyabove95wheremoistureisbeingactivelyaddedtoventilatingairitisbesttodosoby
bullAddingmoistureonanintermittentbasis(egthroughpulsing)andor
bullHaveductingbelowthelevelofthefloorsothatanymoisturefallingoutintheductsystemcanbesafelydrainedfromthestore
ACTION POINTS
HuMIdItY
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
36 S T O R E m a n a g E R S rsquo g U I D E
excessivecooling-fanorrefrigerationrunningcostsMajorair-leakagepointsareobviousasdaylightcanbeseenthroughthegapsfrominsideadarkstore(Figure153)Otherleakssuchasgapsbetweencompositepanelsmayonlybeidentifiedbydetectingdraughtsonawindydayorbyuseofequipmentsuchasathermal-imagingcamera(Figure152)SimplesolutionscanoftenhelpminimiseairleakageandconsequentlyreduceenergyuseP2
Useofinvertersorvariable-frequencydrives(VFDs)onfansandpumps
Inverters(Figure154)canimprovetheenergyefficiencyoffansandfridgecomponentssuchascondensersfansandcompressorsbymovingawayfromalsquoonesizefitsallrsquoapproachInsteadtheymatchtheperformanceofequipmenttothestorersquosneeds
AfanwillconsumeenergyequivalenttoitscapitalcostwithinaslittleasoneseasonSowhenupgradingequipmenttheextracostofnewtechnologyoramoreefficientmotorneedstobeoffsetagainstpotentialenergysavings
optimisedenergysavingsGoodcontrolisessentialinprovidingoptimalstorageconditionsatthelowestenergycostComparedwithmanycapitalinvestmentoptionscontrolisgenerallyquitecheaptointegrateintoanexistingstoreTheabilitytoregulate
15 Energymanagement
ThebiggestconsumerofenergyduringstoragewhetherusingambientorrefrigeratedairisforcoolingthecropWithever-increasingenergycostsahigherprofileforenvironmentalissuesandthecarbonfootprintofstorageunderstandingenergyuseandexploringenergy-savingoptionsarenowhighpriorities
EnergymonitoringMonitoringconsumptionisakeyfactorinmanagingenergyusesuccessfullyItisarelativelycheapexercisetoundertakeandallowsmanagerstoidentifyhighenergyuseequipmentandtimesspotwhereproblemsmightbeoccurringandmakerationalinvestmentdecisionsonenergy-savingequipment
Energymonitoringcanrangefromtheregularorganisedreadingandmanualrecordingofutilitymetersonsitetotheuseofsophisticateddata-loggingequipmentItcanbeappliedtowholesitesorbysub-meteringtoindividualbuildingsandindividualpiecesofequipment
IfmeteringeachstoreseparatelyisnotpracticalenergyuseperstorecanbeestimatedfromfanandfridgehoursruntimeForeachstoretotalthepowerratinginkWorhpstampedontheelectricmotorsthatrunwhentheambientair-coolingisoperatingandwhentherefrigerationisrunning
ComparingthecostofcurrentelectricitysupplierswithothersupplierscontractsorchangingtariffsmaybeawayofsavingmoneySpecialistenergybrokerscanassistwiththisprocess
BuildingimprovementsLeakageofwarmambientairintostoresthroughgapsinthestructurejointsanddoorsisaprimarycauseof
descriptionmeasures Potentialenergyreduction kWhpertonnesaving
Energymonitoringmanagement 10overall 10kWh
Buildingimprovements Upto20 15kWh
Advancedcontroltechniques 10 75kWh
Invertersonfanspumpscompressors 30 6kWh
Coolingtechniqueoptimisation 20 15kWh
Note The savings are broad estimates relating to the technique in question The cumulative saving from some of the measures is not necessarily additive as some improvements may make others less effective
Table 151 Summary of energy saving optionstechnologies and potential
refrigerationrunningcostexample
Sumofratingsofcompressorandfanmotors=20kW
CostofelectricityperkWh=10p
Numberofhoursfridgerunsinoneweek=45hrs
Totalcost=20x010x45=pound90
Motors have a low power factor so use more metered power than their kW rating But as they rarely run at full motor power this estimate is reasonable
Figure 152 Thermal-imaging camera
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
37S T O R E m a n a g E R S rsquo g U I D E
refrigerationtocoincidewiththecheapernighttariffcanmakesignificantcostsavings
Web-basedforecastingsystemsarebecomingavailableonsomeinternet-connectedstorecontrollerstoanticipatecoolweatheranddelaycoolinguntilcoolambientairisavailable
Knowwhereitisgoing
bullInstallasub-meteronthepotatostoreorevenindividualpiecesofequipment
bullReadmetersregularlyndasheithermakemanualrecordsoruseautomatedSMARTmetering
bullAnalysetheinformationyougatherandtrytorelatepeakstoparticularactivities
Stopanyleaks
bullCheckdoorslouvresandjointsndashsealgapswithbrushsealsrubberflapsorsprayfoam
bullCheckinsulationndashrepairdamagedareas
bullConsiderimprovementsndashwhereinsulationisbelow50mmconsiderincreasingitsthickness
ACTION POINTS
EnErGYMAnAGEMEnt
Beincontrol
bullInstalltariffcontroltocapitaliseoncheapnight-ratetariffs
bullRemotediagnosticsandmultipointtemperaturesensingwillhelpyoumonitorhowyourstoreisrunningandallowproblemstobeidentified
Considertherunningcosts
bullWhenupgradingequipmentbalancethecostofequipmentagainstitsenergy-savingpotentialndashnewtechnologyorhigher-efficiencyoptionsmayoffersignificantcostbenefit
Carryoutanenergyaudit
bullConsiderengagingaspecialistenergy-auditingservicewhichwillhighlightwhereenergysavingscanbemade
Figure 153 Whilst this store looks well constructed major air-leakage points can be seen inside the store when dark
Figure 154 Inverters
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
38 S T O R E m a n a g E R S rsquo g U I D E
16 Storeatmosphere
areoftenintheregionof03ndash05(3000-5000partspermillion)whichisabout10timesthe004levelnormallyfoundinair
ModernhighlysealedstoresaremorelikelytohavehigherlevelsofcarbondioxideiftheairwithinthestoreisnotfresheneddailyCarbondioxidecanaccumulatetolevelsashighas3attimesofhighcroprespirationCroprespirationratesarehigherimmediatelyafterharvestfollowingthethermalapplicationofsproutsuppressantsandalsowhenusingethyleneinstore
AdherencetoHealthampSafetyExecutiverecommendationsforoperatorexposurelimits[wwwhsegovukcoshhtable1pdf]ensuresasafeworkingenvironment
ManystoragecontrolsystemsarenowavailablewithCO2sensorsallowingmeasurementandcontrolofthestoreatmosphereautomaticallyPortableCO2sensors(Figure162)canalsobeusedtomonitorlevelsattimesofhighcroprespirationbutarerelativelyexpensivetopurchaseThemainpriorityforthepotatocropistocontrolexcessivebuild-upAsimpletimercontrolcanautomatethisprocesswithouttheneedtomeasurethecarbondioxidelevelThiscanbeachievedmostsimplybyrunningcontinuouslyasmallextractorfanfittedinthestorewallorbyventilatingforafewminuteseachdaytoletsomeambientairintothestoreManycontrollersnowfeaturethistypeofcontrolintheformofalsquoflushrsquoorlsquopurgersquofacilityBeawareofpossiblerisksofproblemssuchascondensationorchillingwhenflushingstoreswithambientair
EthyleneEthyleneaplantgrowthhormonecanbeacomponentofthestoreatmospherewhereitisusedasasproutsuppressanttreatmentP18Whereitisusedethylenecaninfluencecroprespirationratessointeractionsarelikelywithotheratmosphericcomponentsegoxygenandcarbondioxide
othergaseouscomponentsInadditiontocarbondioxidethereareothergaseouscomponentsinthestoreatmosphere(volatilecompounds)whichareassociatedwithpotatoesandthedevelopmentofsomediseasesSomeofthesehavebeenidentifiedbuttheirinfluenceonpotatoqualityisstillbeinginvestigatedHoweveritisknownthatvolatilecompounds(includingethylene)canbeintroducedtothestorethroughprocessessuchasthermalfogapplicationP18andthesemayhaveadetrimentaleffectoncropqualityiftheyareallowedtopersistinthestore
Theidentityofothervolatileswithinapotatostoreremainsunknownandtheirroleisthereforenotyetunderstoodsomeresearchhasbeenundertakenanditishopedinfuturetobeabletousemeasurementofthesechemicalcompoundstodevelopsystemsforearlydetectionofdiseasessuchassoftrot
oxygenPotatoesarelivingorganismswhichrequireoxygentometabolisetheirfoodreservestomaintainlifeRespirationratesareusuallyhigherinprocessingstorescomparedwithpre-packstoresduetotheirhigherholdingtemperaturesButrespirationratealsoincreasesthefurthertheholdingtemperaturefallsbelow5degCP3
Alackofoxygeninapotatostorecanleadtoblackheart(Figure161)wherethecentralcoreofthepotatoisstarvedofoxygenandthetubereffectivelysuffocatesfromtheinsideoutTheresultisanodourlessblackenedareainthecentralpithtissue
Undernormalatmosphericconditionsthelevelofoxygeninairis21Alevelof19oxygenistheminimumacceptableforworkersafety(ConfinedSpacesRegulations1997)
CarbondioxideNormalrespirationofpotatoesinstoreproducescarbondioxide(CO2)whichwillaccumulateinthestoreatmosphereThelevelsofcarbondioxideinapotatostore
Figure 161 Blackheart
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
39S T O R E m a n a g E R S rsquo g U I D E
Croprespiration
Respirationratesareusuallyhighatstoreloadingsoitisnecessaryto
bullMaintainagoodsupplyoffreshair
bullReducecroptemperaturequicklyinverywarmharvestingconditions(gt20˚C)
bullIfusingethyleneintroducegraduallytoreduceimpactonrespirationrateIncreasedrespirationresultsinmoreheatwhichthenrequiresmoreenergytoremove
Carbondioxide
bullMonitorCO2levelsduringcriticalphasessuchasstoreloadingandcuring
bullAvoidbuild-upbyrunningasmallfantocontinuouslybleedfreshairintosealedstoresThisisbestdonebyfeedingexternalairintothefantoallowcomprehensivemixingbeforedeliverytothecrop
bullAlternativelyopenpersonneldoordailytotheoutside
bullIfpossibleautomateflushpurgefunctiononstorecontroller
bullEnsurelevelsarewithinHSEguidelinesforoperatorsafety
thermalfogapplications
bullFlushstoreassoonaschemicalhasdepositedndashprolongedexposuretocombustiongasesresultsindarkerfrycolour
ACTION POINTS
StorEAtMoSPHErE
Figure 162 Using a meter to measure carbon dioxide
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
40 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
accuratemeasureofelectricitycostswhichmayonlybeestimatedotherwise
Storagelossesndashtheproductioncostshavetobecarriedbywhatcanbesoldsoallowancesshouldbemadeforweightlossandoutgradeswhichdonotmeetmarketspecification
Capitaldepreciationndashcostpertonneperseasonegastorecostingpound150pertonnewitha25yeardesignlifewouldcostpound6tonneyearInaboxstorethecostoftheboxwillneedtobeaddedboxesshouldrealisticallybecostedovera10-yearlifeBeyondthisrepairswillgenerallyberequiredtoextendtheiruse
FinancendashthecostofborrowingoropportunitycostsofthemoneyinvestedinthestoreandcropThisshouldincludeinterestonthepricedifferentialbetweenharvestandunloading
riskprofitndashtoberealisticacostshouldbeincludedforthevalueofstorage(ietomakeitworthwhile)
CropmonitoringRegularsamplingandassessmentofthestoredcropisvitaltomonitortheconsequencesofanymanagerialactiononpotatoqualityItwillalsosavetimemoneyandaggravationbyavoidingrejectedloadshelpingtooptimisestorageconditionsandminimisingdevelopingproblems
ItisimportanttoknowthecustomerrsquosspecificationsThismeanslimitsforfactorssuchastubersizegreeningdamageskinfinishblemishdiseasesrotsinternaldefectsandfrycolourWhereverpossibleadoptthe
StorageformarketsItcannotbestressedstronglyenoughthatwhenstoringpotatoesthisshouldbedonewithafirmknowledgeofthemarketthatwillbesupplied
StorageisaspecialistactivityandtoachieveworthwhileandrealisticreturnsitisnecessarytobeabletodelivercroptotheprecisespecificationthemarketdemandsIfthemarketisnotknownthissimplycannotbeachieved
SpecificationswillvarywidelywithinsectorsdependingonarangeoffactorsincludingpricepackagingtimelinessandqualitativemeasuressuchasskinfinishdrymattertubercountfrycolourandsugarcontentSomeofthesefactorscanbeinfluencedbystoragemanagementasoutlinedoverleafotherswillnotHoweverifacropdoesnotmeetspecificationbeforestorageitisnotgoingtodosoafterwardsandthereislikelytobenovaluewhatsoeverinincurringtheexpenseofstorageinthesecircumstances
SocropsmustalwaysbeassessedinrelationtothismarketbothbeforeandduringstoragetoconfirmthatqualitymeetsthemarketrsquosneedsThesectiononQualityControl(opposite)outlinesproceduresfordoingthis
CostsStoringpotatoescanbeanexpensiveprocessanditisimportanttohaveaclearappreciationofthetruecostofstoragebeforecommittingacroptoit
Theprincipalcomponentsofstoragecostsare
runningcostsndashegelectricitychemicalspropertyrepairsloadingequipmentmaintenancemonitoringandinsuranceThemoreaccuratelythesecanbemeasuredthemorerealisticanyestimateofcostswillbeForexampleinstallingasub-meterinastorecangivean
Figure 172 Regular sampling and assessment of the stored crop is vital
Figure 171 A good quality sample
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
41S T O R E m a n a g E R S rsquo g U I D E
Maximumlevelofdefectpermittedbymarket
20
10
5
2
1
Minimumnumberoftubersrequiredtodetectdefectispresent
15tubers
30tubers
60tubers
150tubers
300tubers
Minimumnumberoftubersrequiredtoestimatethelevelofthedefect
45tubers
90tubers
180tubers
450tubers
900tubers
(Adapted from EC Directive 200263EC at 95 confidence level)
Table 173 Number of randomly selected tubers required to find defects in a stock
customersrsquomethodsforassessingqualityandensureallaspectsofthespecificationaretestedUsethesamemethodforeachsamplewriteitdownandsticktoit
UseresultstosupplyonlycropsthatmeetthemarketrsquosspecificationIdentifylsquoborderlinersquocropsandnegotiatetheseseparatelyorsupplythemtoacustomerwiththeappropriatespecification
GettingthebestfromQCCarryoutafullinspectionbeforestorageStorageiscostlysoitisimportanttobesurethatthecropgoingintostoreisworthstoringIfitdoesnrsquotsatisfythespecificationbeforestorageitwonrsquotafter
TreatQualityControl(QC)asaninvestmentItwillgiveusefulfeedbackonchangestoacropinstorewhichwillhelpdecision-makinglaterFollowingafullinitialinspectionatharvestcontinuetomonitoronlyfactorsthatarelikelytochange(egsproutingrotsfrycolourand
certainblemishdiseases)everymonthFullyassessloadsbeingdeliveredtocustomersandusetheirintakereportsasanauditofQCatthestoreAnymajordifferenceswillneedinvestigatingfurther
SamplingAsampleshouldbelargeenoughtorepresentastockadequatelyTable173providesaquickreferencegivingthenumberoftubersrequiredtosampleforagiventolerance
Manystoremanagersareguiltyofsamplingatasinglepointorlevel(egthetopofthestore)butthisisunlikelytogiveasamplethatisrepresentativeThemoresub-samplelocationsthebetterTakeatleasttwosub-samplesfromeachstockbutonesampleisstillbetterthannoneAseparatesampleisrequiredforeachstockcropsfromdifferentfieldsorstorescountasdifferentstockseveniftheyarethesamevariety
Figure 173 A full QC inspection prior to storage is a sound investment
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
42 S T O R E m a n a g E R S rsquo g U I D E
17 Storageformarkets
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
43S T O R E m a n a g E R S rsquo g U I D E
Processing FreshPre-pack SeedMarketdemands bullUniformandacceptablefrycolour
bullLowlevelsofrotandskinspot(increasespeelingwaste)bullFreedomfromsproutingbullDrymatterappropriateformarketbullControlleduseofsproutsuppression
bullBrightshinyskinsbullLowlevelsofscuffingdamagebullLowlevelsofblemishdiseasebullFreedomfromsproutingbullMinimalresidues
bullSpecificsizerequirementbullLowlevelsofdiseasebullFreedomfromsprouting
Managementprinciplesinfield bullPlantoharvestmaturecropsbeforesoiltemperaturesdipsbelow8degCbullAgronomy(egcanopymanagementseedselectionplantingdensity
andnutrition)tocontributetoachievingsizeandmaturitythatpermitslongtermstorage
bullPlantominimisetimeinfieldtoavoiddiseasedevelopment
bullBearingaboveinmindagronomytofocusonachievingsizeandskin-setthatallowsliftingtominimisedamage
bullHarvestwhendrybullMinimisedamageandbruising
bullPlantoharvestcropswithminimaldamageandfollowprocedurestokeepcropsdry
bullFungicideapplication(forcontrolofdiseaseinthedaughtercrop)cantakeplaceeitheratloadingorunloading
Storemanagementpre-holding bullMaintainwarmtemperatureatc10-15degCafterharvesttoensureanydamageisfullycured
bullOnlylowertemperatureverygradually(max03degCday)oncecuringiscomplete
bullIncropsathighriskofsweeteningkeeptemperatureshigh(10-13degC)forfirstweeksofstorage(pre-conditioning)wherediseaselevelsandsproutingpermit
bullMonitorfrycoloursandsproutingregularly
bullCuringandpull-downstrategydependsonfinalmarketandlikelihoodofdiseasedevelopmentP11
bullIngeneralcuringwillberequiredfordamagedcropsorskinspot-susceptiblevarietieswhereasitcanbeomittedifpreventingdevelopmentofsilverscurfandblackdotisessential
bullAimtopull-downtemperaturesatc05degCperdayPreventionofcondensationisimportantduringcuringandpull-downP12
bullSeedcropswillgenerallyrequiredrycuringbullProtractedloadingperiodandmultiplestocksvarieties
indifferentphysiologicalstatesmeancondensationriskishigh(hightemperaturedifferentialsbetweenstocksarecommon)Risksreducedbyregularpositiveventilation
bullAsaccesstostocksisoftenrequiredthroughoutstorageindividualletterboxlsquolanesrsquothatcanbeswitchedonandoffarepreferred
Storemanagementholding TemperaturedependsonusevarietyandstoragedurationExamples
Hermes 9-12degCLadyRosetta 8-10degCSaturna 8-10degCMarisPiper 7-11degCMarkies 8-10degCPentlandDell 85-10degCRussetBurbank 65-85degC
bullThelowerendofthescaleisappropriatefor6-9monthstoragethehigherendshouldbeusedforshorterdurations
bullDailycontrolledflushingwithfreshairrequiredtopreventbuild-upofCO2P18
bullItisimperativethatsproutingisavoided(inpreparationforsproutingtuberswillconvertstarchtosugarsandfrycolourwillbeadverselyaffected)andapplicationofsproutsuppressant(egCIPC)willbenecessaryforlongtermstorage
bullFollowingbestpracticeguidanceisessentialtoavoidexceedingMaximumResidueLevelsP18
bullHoldingtemperatureswhicharelowerthanrecommendedoftenasaresultofprolongedperiodsoflowambienttemperaturecanresultincold-temperaturesweeteningwhichwillaffectfrycolourThiscanbemadeworsebywarmingthecrop
bullHoldingtemperaturesvaryfrom2to5degCdependingonvarietymarketstoragedurationandfridgecapabilities
bullAsproutsuppressantwillberequiredinhighertemperaturestoresEthyleneisanoptionforfreshmarketintroducetreatmentgraduallytominimiseanystressonthecropConsultwithyourethylenespecialistpriortouseP18
bullPreventionofsproutgrowthisimportantandrequirestheuseofrefrigerationespeciallyforstorageafterChristmas
bullAholdingtemperatureof3degCisoftenusedtoholdcropsthroughtowhenseedisremovedfromstoreinthespring
bullAirflowsmaydifferfromfreshstoragebecauseseedisgenerallysmallandpackstogethermoretightlywithinabox
bullAsgradingtakesplaceensuremaindoorswithinrefrigeratedholdingstoresstayclosedwheneverpossibletoreducetheriskofcondensation
unloading Poorfrycolouratthisstageisusuallytheresultofoneoftwothings-bullLowtemperaturesweeteningndashthismaybealleviatedby
reconditioning(storingatc15degCpriortounloadingtoincreaserespirationandldquoburnoffrdquosugars)althoughthisisveryvariableandfurtheradviceshouldbesoughtonacase-by-casebasis
bullSenescent(oldage)sweeteningndashthisislargelyirreversible
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
bullAimtowarmcrop(gt8degC)beforeharvestingtoreducedamage
bullWarmedcropsshouldbestoodtoequilibrateforadaythisallowsskinstobecomemoreelasticandreducesthumb-nailcrackingP19
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
44 S T O R E m a n a g E R S rsquo g U I D E
dioxideNewguidelinesrequireethyleneconcentrationtobeincreasedverygraduallyuptothe10ppmholdingconcentrationtolimitrespiratoryresponsesAsitisarelativelynewmethodofsproutcontrolitisimportantforstoremanagerstofollowsuppliersrsquoinstructionsclosely
MaleichydrazideMaleichydrazideisappliedtothegrowingcropinthefieldCanopyconditionandweatherconditionsatthetimeofapplicationareimportantfactorsgoverninguptakeandthereforeitssuccessfuluseMHcanbeusedtolimitsubsequentCIPCusebutisusefulasastand-alonesproutsuppressantonlyinsituationswheresproutingriskisrelativelylow
Chlorpropham Chlorpropham(CIPC)isthemainsproutsuppressantusedinBritainandvirtuallyallisappliedasahotfog(Figure181)CIPCissuitableinbothprocessingandpre-packingstoragesystemsThechemicalisfoundasaresidueanditsuseisnowsubjecttoaPotatoIndustryStewardshipActionPlan(seewwwpotatoorgukcipc)CIPCuseislimitedto36gtonneseasoninpre-packstoresand6375gtseasoninprocessingstoresorwherethecropwillbepeeledTheseadditionalrestrictionswereintroducedtohelpensurecompliancewiththeMRLStoremanagersshouldbeawarethatanybreachesoftheMRLarelikelytoresultintighterrestrictionsonCIPCuseandcouldextendtoitscompleteremovalAlthoughmostCIPCisappliedbyacontractoritremainsthestoremanagerrsquosresponsibilitytoensurethatapplicationsarejustifiedandallstatutoryconditionsofusearemet
18 Sproutsuppression
AtharvestpotatoesareusuallydormantandsproutingdoesnotoccurevenunderconditionsfavourableforgrowthTheperiodofdormancyvariesconsiderablybyvarietyandseasonAfterbreakofdormancysproutsgrowatarateprimarilydeterminedbytemperatureReducingstoragetemperatureisthereforeaneffectivewayofcontrollingsproutingbyfirstprolongingdormancyandthenlimitingtherateofgrowthToavoiduseofsproutsuppressantsentirelystoragetemperaturesneedtobeconsistentlybelow3degCHoweverpotatoesheldatsuchcoldtemperatureswillbeaffectedbylow-temperaturesweeteningwhichcanadverselyaffecttastetextureandcolouronroastingfryingInpotatoesstoredforprocessingwherelow-temperaturestorageisnotanoption(becauseofpoorfrycolour)theuseofsproutsuppressantswillbenecessaryforallbuttheshorteststoragedurations
Chemicaltreatmentswithchlorpropham(CIPC)maleichydrazideandethyleneareavailableforsproutsuppressionTheprincipalcharacteristicsofthesecompoundsareshowninTable182Someproductionprotocolsrestricttheuseofcertainactivesubstances
EthyleneEthyleneisaneffectivesproutsuppressantoflowtemperaturestoredcropsItsuseisnotcontrolledbyanMRLhenceitslsquoresidue-freersquostatusfavouredbysomemarketsEthylenehaslittleresidualeffectonsproutgrowthwhichwillresumesoonafterremovalofcropsfromstore
EthyleneisaplanthormonewhichhasthepotentialtomarkedlyincreasetuberrespirationrateandasaconsequenceincreasestorecarbondioxidelevelsP16Problemswithtasteandtexturemodificationpreviouslyassociatedwithethyleneinsomevarietiesarebelievedtohavebeencausedbyinteractionwithhighlevelsofcarbon
Figure 181 Hot-fog application of CIPC
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
45S T O R E m a n a g E R S rsquo g U I D E
Minimisationstrategies
bullSegregatebydormancyndashvarietieswithcontrastingdormancycharacteristicsshouldbeheldinseparatestoressothatonlycropsrequiringsuppressantsaretreated
bullCIPCrequirementscanbelimitedbyuseofethylene(ware)andmaleichydrazide(wareampprocessing)ndashbutcheckmarketacceptabilityfirst
bullVarietieswithlongdormancyandlowtemperaturetolerancereduceneedforsuppression
CIPCApplication
Storeselection
bullBulkstoresfittedwithinverters(variablefrequencydrives)forfogrecirculationaremostefficientforCIPCuseandpreferableforvigoroussproutingandorlong-termstorage
bullUsethefansoperatingatslowspeedtoassisttheapplicationprocess
bullInlsquooverheadthrowrsquoboxstoresanopenstackingpatternwithpalletslotsalignedaidsdispersalCreateacoveredplenumtoapplyfogintoThiswillstopfogenteringtheroofspace(seePotatoCouncilGrowersrsquoAdvice)
bullForpositivelyventilatedboxstoresitisbesttousetheventilationsystemforapplicationbutthisislikelytoneedsomewayofslowingfanspeedsdownConsultthecontractorchemicalsupplier
bullMinimisesproutingpressurebyselectingstoresmostabletomaintainthedesiredtemperature(iewitheffectiveinsulationlowleakagerefrigerated)forlongtermstorage
Storeloading
bullLooseandadheringsoilincreasesCIPCrequirement
ACTION POINTS
SProutSuPPrESSIon
bylimitingmovementofthechemicalOnlyharvestundersuitableconditionsandtakeallreasonablestepstoextractsoil
bullInboxstoresalignpalletslotsasfaraspossibleandleavespacearoundtheapplicationportforfogtodisperseTheductcarryingfogintoastoremustneverbedirectedatcrop
Whentoapply
bullCropsshouldbedrycuredandhaveaneventemperature(ideallywithin1degC)atthetimeofapplicationTemperaturedifferentialscanbereducedbyanextendedperiodofrecirculation
bullDonotdelayCIPCusejustbecauseacropisnotatholdingtemperaturendashitisbettertoapplytoacropthatiswarmanddormantthancoolandsprouting
bullRefrigerationandhumidificationsystemsshouldbedisabled12-24hoursbeforefogging
Application
bullInitialtreatmentwillonlybesuccessfulifappliedtodormantcropIfsproutingisevidentattimeofapplicationuseahigher(label)rateandprepareforareducedstorageduration
bullRe-applicationshouldtakeplacewhensignsoffreshsproutgrowthareobservedlsquoTimedrsquoroutineapplicationsshouldonlybemadeinalowCIPCdoseregime
bullStoreleakinessisdramaticallyincreasedinwindyconditionsSealstoresP1anddonotallowapplicationstobemadeunderwindyconditions
Processingquality
bullTheprocessofhot-foggingintroducesby-products(includingethylene)tothestorewhichdarkensfrycolourForprocessingcropsventilatethestoreassoonasthefoghassettled
Activesubstance Applicationmethod notes MrLmgkg
Ethylene Gasappliedbydirect bullEffectiveoncropsheldattemperatureslt5degC releaseorgenerated bullNotusedonprocessingbecauseresultsare in-store unpredictableandthereisaneffectonfrycolour none
Maleichydrazide(MH) In-fieldfoliarspray bullProvidesvolunteercontrol bullAmodestsuppressantoftenfollowedbyCIPC bullResultsfromMHvarydependingonweather andcanopyconditionattimeofapplication 50
Chlorpropham(CIPC) Hot-fog bullCommonlyusedsproutsuppressantinGB bullRatesofuselimitedacrossproducts bullStewardshipplaninplace bullTreatedstorescannotbeusedforanyseeds 10
maximumresiduelevelpermittedinpotatoesforsale
Table 182 Sprout suppressants for use in potato storage
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
46 S T O R E m a n a g E R S rsquo g U I D E
Figure 192 Fingernail damage
cropbeingwarmedmustbekeptatthistemperature
Allowingboxestowarmnaturallyoverfourdaysinabuildingkeptat8-10oCisthesimplestwayofwarmingbutthisrequiresabufferstorageareafourtimesthedailygradingrateIfthecropisbelowtheambient-airdew-pointtemperaturecondensationmayformonthecropextendingthewarmingtimeandexposingthedamppotatoestoinfectionbydiseaseForcedwarmingsystemsliketheletterboxsuctionwallordryingtentwhichtakeanighttowarmand24hourstorecoverskinmoisturerequireawarmingareatwicethedailyrateofgrading
dryingofskinswhenwarmingWhenventilatingthecropwithwarmairthetuberskinslosemoistureThismakestheskinsinelasticandmoreliabletotearinggivingrisetolsquofingernailrsquodamage(Figure192)Inrapidwarmingsystemsskinsshouldbegiven24hourstorecoverandrehydratepriortograding
19 Warming
Potatoesgradedbelow8oCaresusceptibletoimpactdamagesplittingorbruisingAnywoundsthatresultwillhealslowlyatcoolertemperaturesandmaymakeacropunsuitableformarketTominimisetuberdamageandspeed-upwoundhealingparticularlyfordiseasecontrolitisrecommendedthatcropsbelow6oCarewarmedbeforegrading
PhysicsofwarmingTowarmpotatoesto10oCthewarmingairshouldalsobeat10oCTherateofwarmingisdependentontheflowofairbetweenthetubersIfboxesofpotatoesat3oCareplacedinagradingareaat10oCnaturalconvectiveventilationwillwarmthemupinaboutfourdaysHoweverifairisforcedthroughtheboxestherateofwarmingwillincreasewiththerateofairflow
Atadeliveredairflowrateof08m3st(around04m3stthroughthepotatoesafterleakageistakenintoaccount)warmingacropby6oCwilltake10-12hoursButifthecroptemperatureisbelowthedewpointofthewarmingairthewholeprocessisextendedThisisbecausewatervapourintheairwillcondenseonthecropThismoisturewillthenneedtobedriedcoolingthepotatoesbyevaporationbeforethecropstartstore-warm
WarmingoccursprogressivelyineachboxlikeadryingfrontP9withthewarmingfrontmovingverticallyinletterboxwarmingsystems(Figure191)andfromside-to-sideinsuctionwallsystems
WarmingsystemsHeatedaircanbedeliveredeitherbyforceddelivery(blowing)orextraction(suction)Inblowingsystemsheatcanbefedintothefantobringthetemperatureofthewarmingairupto8-10oCWarmingcanbedonewithinthecoldstoreorinanon-heatedbuildingInsuctionsystemstheairbeingsuckedintothecropneedstobewarmedto8-10oCwhichmeansthattheatmospheresurroundingthe
Figure 191 Letter box system suitable for warming
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
47S T O R E m a n a g E R S rsquo g U I D E
Figure 193 Warming the crop prior to handling can significantly minimise bruising
Warmingforfreshpre-pack
Whenwarmingforpre-packitisimportanttopreventimpactdamagebruisingandlsquofingernailrsquomarksFingernailmarkingshouldbelessofanissuewherepotatoesarewashedastheskinsareslipperyandthetearingactionofdryskinonadrysurfaceisnotaproblemInthissituationa24-hourskin-recoveryperiodisunnecessary
bullIfpotatoesaretobegradedwetcropcanbewarmedovernightforgradingnextmorning
bullIfcropistothegradeddryallowa24-hourrecoverytimeafterovernightwarmingbeforehandling
bullIfnaturalwarmingbyconvectionisanoptionthengradeoncethecropisat8-10degC
Warmingforseed
SeedbeingsmallerthanwareislesspronetodamageButasseedisgradeddryfingernaildamageismorelikelyandforsubsequentdiseasecontrolfastwoundhealingisvital
bullFollowdry-gradingrecommendationsabove
ACTION POINTS
WArMInG
bullAftergradingkeepseedwarmandventilatedfor2-3daystoallowanyfreshdamagetocureproperlybeforereturningtocoolerstorage
Safewarming
Thesafestwaytowarmpotatoesistoensurethatthecroptemperatureisneverbelowthedew-pointtemperatureofthewarmingairThiswillavoidanywettingbuttheonlyplacethatthisconditionexistsisinthecoldstoreIfthecropisat35degCthedew-pointtemperaturemustbelessthan35degCIfthecropiswarmedinthestoretheventilationorrefrigerationsystemremovesanyheatthatdoesnotenterthecrop
bullWarmseedpotatoesincoldstoretopreventcondensationandpossiblediseaseinitiation
bullIfseedisremovedfromstorecoldwithoutwarmingwarmrapidlytominimiselengthoftimecropiswetfromwarming
bullUseindirectdieselspaceheatingtowarmmosteconomicallyUseanelectricheaterinmobile-heatingsystemsfittedwithRCBprotectionforsafety
bullAlwaysuseathermostatforsafetyandtominimiseenergyusewhenheating
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
48 S T O R E m a n a g E R S rsquo g U I D E
20 Storemonitoringampqualityassurance
informationcanthenbelinkedtostockslocatedintheproblemareas
StoremonitoringStoretemperaturesandcontrolsshouldbecheckeddailyTemperatureinformationisthemostcriticalandasimplelogofkeyprobereadingscanbekeptmanuallyorprintedoffdailyItisalsousefultoknowhowlongthehardwarehasactuallybeenrunningHourmeterscanbeeasilyfittedtomostequipmenttoprovidethisinformationStocksofpotatoesshouldbecheckedweeklyPermanentladdersandwalkwaysshouldbefittedtoallowsamplingfromthetopofthestoreinsafetyP21
Manystore-controlsystemsnowofferfacilitiestologinformationonacomputer(Figure201)Makesuretheoutputisclearorinaneasy-to-interpretgraphicalformatIncreasinglysystemsalsooffercomputer-basedcontrolinadditiontomonitoringandloggingTheseofferusefulanduser-friendlyfeaturessuchastouch-screenoperationgraphical-userinterfacesremotedial-upmonitoringandtextalerts
InadditiontoroutinemonitoringthereshouldalsobeproceduresinplacetoassessthecropregularlyP17
QualityassurancePotatoproductionandstorageisincreasinglysubjecttoquality-assuranceproceduressuchastheAssuredProduceSchemewhichincludetraceabilitycarefortheenvironmentandminimisationofrisktotheconsumerGoodrecordkeepingisalsoabenefittomanagementasitcanquicklyidentifyweakpointsinaproductionsystem
RecordkeepingshouldbedesignedsothatallinformationonabatchofpotatoesiskepttogetherReasonsforanyproblemcanthenberapidlyidentifiedAllactiontakenshouldberecordedonthelogforabatch
StorediaryItisimportanttokeepastorediarytorecordgeneralstoremanagementinformationrelatedtoallthestocksheldwithinthestoreThiswillincludemajoreventssuchasloadingorachemicalapplicationandregularstoreinspectionsforcondensationdehydrationrotsorblemishdiseasesWheredetailedindividualstockrecordsarekeptitisunlikelythattheyandthestorediarywillcometogetherunlessthereissomesystemsetuptolinkthetwoThiscanberesolvedbykeepingadetailedrecordorplanshowingwhereeachstockislocatedinthestoreInspection
Figure 201 Computerised systems offer comprehensive control options
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
49S T O R E m a n a g E R S rsquo g U I D E
toPFArMLIMItEd PotAtoStorAGErECordSHEEt
StorEFarmyard 2 CroP Maris Piper Field 10
Dateamptime CROPTEMPdegC AIRTEMPdegC FANS FRIDGE Comments
Set-pt Ave Minsensor Maxsensor External Storeave Hours Run Hours Run
149 800 120 134 132 S1 139 S8 131 136 1235 mdash 739 mdash Dry curing
159 840 120 130 129 S1 133 S6 128 132 1255 20 747 8 Fridge OK
169 815 120 127 125 S1 130 S6 165 137 1279 24 754 7 Ext air off
Figure 202 Example store diary sheet
Qualityassurancerecords
Recordsareneededtosatisfyquality-assuranceprotocolssuchastheAssuredProduceSchemeNaturersquosChoiceUKROFSorin-houseschemesTheydemonstratetobuyersthatacropisbeingproducedaccordingtoanagreedprotocol
bullKeeprecordsavailableforinspectionbybuyersatanytime
bullUpdaterecordsdaily(Figure202)togivefastaccessshouldproblemsoccur
bullEnsurestorediaryrecordscanbelinkedtostockrecordstofindproblemsrelatingtostoredesignormanagement
recordstoassesscropstandard
ItisimportanttoknowthequalityofproductbeforeitleavesthestoragepremisesThismayincludefrycolourtestsblemishdiseaseandskin-damageassessmentsGoodsamplingbeforedispatchcanhelpavoidtheproblemofrejectionondelivery
bullAssessproductbeforeitleavesthestoreusingmethodsasnearaspossibletothosethebuyerwilluseonreceipt
bullKeepsamplesofallproductsoldfortheperiodoverwhichanyproblemsmayoccuregaweekforpre-pack6-8weeksforseed
Seedpassports
SincemanydiseasesoncropscanhaveoriginsintheseedusedseedpassportsareincreasinglybeingrecommendedWhilehusbandryfactorssuchasdateofplantingandliftingareusefuladiseaseassessmentofstockBEFOREgradingisessential
bullProvideallseedwithseedpassportsincludingkeyagronomicdatesplusvarietygradeandsize
bullRecorddiseaselevelsbeforegrading
bullRecordseedtreatment(ifany)
bullRecordtemperatureondispatch
Sendleafletwithloaddetailingactiontobetakenbygroweronreceipt
Servicestoreequipment
Regularservicingofstoreequipmentreducesthechanceofbreakdownswhichcancompromisequalityiftheyoccuratcrucialtimes
bullEnsureallequipmentisservicedandcheckedannually
bullKeepservicerecordstodemonstrateduediligence
ACTION POINTS
StorEMonItorInG
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
50 S T O R E m a n a g E R S rsquo g U I D E
risksinstoresRiskassessmentisastatutoryrequirementaspartofhealthandsafetylegislationItisrelativelystraightforwardtomakeandrecordanassessmentofrisksineachstoreFollowtheprocessshownintheriskmanagementlsquowheelrsquobelow(Figure211)Riskswhichcommonlyoccurinapotatostoreinclude
bullClimbingampfalling
bullTripping
bullCO2accumulation
bullChemicaluse
bullElectricshock
bullVehiclemovement
bullLighting
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
21 Healthandsafety
ThereareasignificantnumberofregulationswhichcoverhealthandsafetyinandaroundthepotatostoreStoreownersoperatorsandemployeesworkinginpotatostoresmustdoeverythingpossibletoensurethesafetyofthemselvesandothersTheeasiestwaytodothisistocompleteariskassessmentSpecialisthelpisavailabletoadviseonthisprocessindetail
WhenassessingriskitisbesttokeepmatterssimplewhereverpossibletoensureanymeasurestoimprovesafetyarefollowedSoquestionsaskedtofindoutwhattherisksareandwhatstepsarebeingtakentominimisethoserisksshouldbestraightforwardIfmeasuresareinadequateadditionalcontrolsmayberequiredRemembernotdoingsomethingsimplytosavetimeorexpenseisnotanacceptablecourseofactionwheresafetyiscompromised
WorkingatheightThemostsignificantnewpieceoflegislationtoaffectpotatostorageinrecentyearshasbeentheWorkatHeightRegulations2005Potatostorageisnotdeemedtobeashort-termactivitysooneofthemainchangesresultingfromtheseregulationshasbeenthebanplacedontheuseofladdersinstoresWhilealaddercanstillbeusedfortemporaryaccesssuchaschangingalightbulbusingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegalIfaccesstothetopofboxesisrequiredanalternativemeansofaccessmustbeprovidedOnceontopofthestackitisalsonecessarytoprovideaphysicalbarriertoalertsomeonetoanygapsbetweenboxesorproximitytotheedgeofthestack
bullBoxstacking
Animportantaspectoftheriskmanagementprocessisthefeedbackitprovidessoifaparticularriskismeasuredandcontinuestopresentproblemsitcanbere-evaluatedandfurthermeasurestakentominimiseit
FormoreinformationseetheHealthampSafetyExecutivewebsiteatwwwhsegovukpubnsindg401pdforcallthePotatoCouncilrsquosstorageadviceline08000282111
Figure 211 Risk management process
Figure 212 Stepped ladders in a box store
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
51S T O R E m a n a g E R S rsquo g U I D E
Inboxstores(Figure212)steppedladderscanbeemployedtogoodeffectEachladderallowstheoperatortoclimbtwoboxestoacoveredboxplatformfollowedbyanothertwoboxclimbandsoontothetopofthestackUsingaladderforregularaccesstothetopofastoreovertwometreshighisnotlegal
Insistthatallpersonsonsitearehighlyvisibleandwellequippedtoworkinastore
Besuretologvisitorsinandoutsothattheycanbeaccountedforinanemergency
Donotallowexternalpersonneltoaccessthestorewithoutadetailedbriefingonthestoreconditionsandanyassociatedrisks
HEALtHampSAFEtYInStorES
noladdersover2m
Protectedges
Stacksafely
Beseen
AlwaysensurethatboxesarebuilttoBS7611andthattheyareinspectedannuallyandmaintainedingoodorderThiswillhelpreducetheriskofacollapsedstackinsideastore
AtthetopoftheboxstackacaneandhazardtapesystemoneboxinfromanyedgewillhelppreventanyinadvertentaccesstoedgesNotethatagapof200mm(8rdquo)ormoreisdeemedtobeanedge
Hazard tape on 1 metre high canesHazard tape on 1 metre high canes
Access
ACTION POINTS
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
52 S T O R E m a n a g E R S rsquo g U I D E
A1 Bibliography
AdVICEampPuBLICAtIonSPotatoCouncilSuttonBridgeCropStorageresearchPotatostorageadviceandinformationTel08000282111e-mailsbcsrpotatoahdborgukwwwpotatoorguksbcsrPotatoCouncilpublications ProjectSummarySheetsampResearchReportsndashinformationonlevyfundedRampDprojects GrowersrsquoGuidesndashseedproductionandstorageadvice PestsampDiseasesHandbookndashreferenceguide ProductGuidendashpotatosproutsuppressantactivesubstancesanddoseratesAvailablefromPublicationsDeptAgricultureampHorticultureDevelopmentBoard(AHDB)StoneleighParkKenilworthWarwickshireCV82TLPotatoCouncilisadivisionofAHDBTel02476692051E-mailpublicationspotatoahdborgukwwwpotatoorguk
rEFErEnCESBriddonAMcGowanGJinaASaundersSrCunningtonACampduncanHJ(2007)ImprovingCIPCmanagementinbulk-storedpotatoesInAbstracts of Papers amp Posters 4th EAPRFNKUEITP Potato Processing Conference Grantham UK 17 January 2007 Burfootd(1997)ControlofheatandmasstransferprocessesincropstoresFinalreportbySilsoeResearchInstituteBedfordforMAFFLondonBurfootdSmithdLoButler-EllisMCdayW(1996)ModellingthedistributionofisopropylN-(3-chlorophenyl)carbamate(CIPC)inboxpotatostoresPotatoResearch39241-251BurtonWG(1989)ThePotato3rd EditionJohnWileyampSonsNewYorkCargillBF(1976)Thepotatostorage-designconstructionhandlingandenvironmentalcontrolMichiganStateUniversityAmericanSocietyofAgricEngineersUSACargillBFBrookrCampForbushtd(1989)PotatoStorageTechnologyandPracticeProceedingsofInternationalSymposiumMichiganStateUniversity1985AmericanSocietyofAgricEngineersUSACIBSE(1989)PropertiesofhumidairSectionCCharteredInstitutionofBuildingServicesEngineersLondonCunningtonACBriddonAduncanHJJinaALaneAGampMillerPCH(2001)OptimisationofCIPCapplicationanddistributioninstoredpotatoesBPCSuttonBridgeCropStorageResearchSilsoeResearchInstituteampUniversityofGlasgowresearchreportforBPCno20016PotatoCouncilCunningtonACBriddonAMcGowanGJinaAandduncanHJ(2005)DevelopmentsinCIPCapplicationanditseffectsonprocessingqualityInAbstracts 16th Triennial Conference of European Association for Potato ResearchCunningtonACMawsonKBriddonAampStoreyrMJ(1992)LowtemperaturestorageforqualitycropsInProductionampProtectionofPotatoes Aspects of Applied Biology 33 205-212CunningtonACampMawsonK(1997)Improvedstorageofpotatoesforthepre-packmarketInCrop Protection amp Food Quality Meeting Customer NeedsBCPCANPPSymposiumProceedingsSept1997BCPCFarnhamEuropeanAssociationforPotatoresearch(1998)Post-harvest engineering for seed potato storage and handling ProceedingsoftheEAPREngineeringSectionmeetingMar1998EngineeringResourcesSACAberdeen(unpubl)FEC(1985)PotatoStorageFarmElectricHandbook2ndeditionFECStoneleighHardyCEBurgessPJampPringlert(1997)TheeffectofcondensationonsporulationonpotatotubersnaturallyinfectedwithHelminthosporium solaniinsimulatedstoreconditionsPotato Research 40169-180HarrisPM(ed)(1991)ThePotatoCrop-thescientificbasisforimprovement2nd EditionChapmanampHallLondonHylmoumlBPerssontampWickbergC(1976)BulkstoringofpotatoesActa Agriculture Scandinavica2699-102HideGA(1992)TowardsintegratedcontrolofpotatostoragediseasesInProductionampProtectionofPotatoesAspects of Applied Biology 33197-204HylmoumlBPerssontWickbergCampSparksWC(1975)TheheatbalanceinapotatopileIampIIActa Agriculture Scandinavica2581-91KneeshawA(2006)EnergystatusreportGBpotatostorageReportfortheBritishPotatoCouncilOxfordParkLJduncanHJBriddonAJinaACunningtonACampSaundersSr(2006)ReviewanddevelopmentoftheCIPCapplicationprocessandevaluationofenvironmentalissuesStudy243finalreportBritishPotatoCouncilOxford60ppPetersJCLeesAKCullendWSullivanLStroudGPampCunningtonAC(2008)CharacterisationofFusarium sppresponsibleforcausingdryrotofpotatoinGreatBritainPlantPathology57262-271PMB(1970ndash1996)SuttonBridgeAnnualReviewsPotatoMarketingBoardLondonampOxfordPMB(1994)PotatoStoragePotatoMarketingBoardOxfordPringlertamprobinsonK(1996)StorageofseedpotatoesinpalletboxesIampIIPotatoResearch39205-240Pringlert(1992)Storeclimateinpalletboxseedpotatostoresusingpositiveandnon-positiveventilationReportforKPAgricultureSACAberdeenPringlertPotterKMcGovernrEampHardyC(1997)ControlofheatprocessesincropstoresMAFFContractreportnoCSA2597MAFFLondonrastovskiAvanEsAet al(1981)StorageofpotatoesCentreforAgriculturalPublishingandDocumentationWageningenTheNetherlands
otHErInForMAtIondEFrAFertiliserrecommendationsforagriculturalandhorticulturalcrops(RB209)StationeryOfficeLondonwwwdefragovuknIABtAGPocketguidetovarietiesofpotatoes(publishedannually)NIABTAGCambridgewwwniabcomnPtCCertificationforpesticideapplicationNationalProficiencyTestCouncilStoneleighWarwickshirewwwnptcorgukPotatoIndustryCIPCStewardshipGroupStewardshipguidanceontheuseofCIPCwwwpotatoorgukcipcSACSeedstorageinformationCraibstoneBucksburnAberdeenAB219TRTel01224711000wwwsaccouk
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
53S T O R E m a n a g E R S rsquo g U I D E
Glossaryofterms
term definitionAirmixingblending Mixingorblendingofrecirculatedandambientaircontrolledbyregulationof theducttemperatureAironairoffTD Temperaturedifference(TD)betweenaircomingonandoffafridgecoilAmbientair AirexternaltothebuildingstructureAnaerobicconditions WherenoairispresentBlemishdiseases DiseaseswhichcauseunsightlymarksontheskinofthetuberBloom ReflectiveshineontubersCompositepanel Factory-madeinsulationpanelwhichshouldhaveanon-flammablecore injectedbetweentwometalskinsmadeofpolyisocyanurate(PIR)Cropset-point TargetordesiredcroptemperatureCuringperiod Aswound-healingperiodDeadband Toleranceeithersideofacropset-pointDewpoint TemperatureatwhichwatervapourinairwillstarttocondenseDifferential DifferenceintemperaturebetweenoneareainastoreandanotherFor examplecropambientairdifferentialwouldbethedifferencebetween thetemperatureofthecropandairdrawnfromoutsideDiseaseexpression DisplayofvisiblediseasesymptomsDiseaseinfection EntryintothefleshofthetuberbybacteriaorfungusDormancy PeriodbetweentuberinitiationinthesoilandgrowthofsproutsDormancybreak When50ormoreoftubershavesproutsof3mmormoreinlengthDuctlowerlimit MinimumallowabletemperatureofairinmainductEEP Expandedextrudedpolystyrene(boardinsulant)FridgeTD Temperaturedifference(TD)betweenaircomingontocoilandevaporatinggas temperaturewithinthecoilHotbox Insulatedcabinetwarmedto32-36ordmCandhumidifiedwithwaterusedfor samplesofpotatoestospeedexpressionofbruisingortoacceleraterottingInoculum InfectiveagentsofdiseaseegfungalsporesbacteriaetcInterstitialcondensation CondensationformingwithinthebuildingstructureLatentheatofevaporation (Hidden)heatrequiredtochangewaterfromliquidphasetovapourphase withnoincreaseinitstemperature(24MJkg)Halfofcoolingofpotatoeswith coolairresultsfromheatremovedbyevaporationLateral SecondarydeliveryductoffmainairductusuallybeneathabulkpileMummify TheprocessofdryingarottentubertoadryshrivelledmassPeriderm CorkyouterskinlayerofpotatoPU Polyurethane(boardorsprayinsulant)unsuitableforcompositepanelsRelativehumidity(RH) Massofwatervapourinairatadefinedtemperaturecomparedwiththe maximumvapouritcanholdatthattemperatureexpressedaspercentageSaturationhumidity Pointwhereaircontainsthemaximummassofwatervapourwhichcanbe heldperunitmassofairatanygiventemperature(=100RH)Softrots BacterialwetrotsSplit-grading SeparatingtubersintotwoormoresizefractionsusuallyatharvestStackcondensation CondensationformingwithinthecropStructuralcondensation CondensationformingonthebuildingstructureSuberisation Layingdownofthechemicalsuberinbetweendamagedsurfacecellsoftuber asfirstpartofperidermformationinthewoundhealingprocessU-Value Heatconductivityofabuildingmaterial(Wm2ordmC)Thelowerthevaluethe betterinsulatedthematerialWetrots Tuberswherethefleshhasbeeninvadedbydiseaseorganismstoform aliquidmasswithlittlestructuralstrengthThewetmasscollapseson unaffectedneighbouringtubersprovidinginoculumandanaerobicconditions whichcanleadtofurtherrottingWound-healingperiod Periodforwoundsoncroptohealtoformabarrieragainstdiseaseingressto thefleshofthetuber
Pnumber Cross-referencetotherelevantnumberedsectionofthisGuide
A2
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
54 S T O R E m a n a g E R S rsquo g U I D E
MetricequivalentsA3
STD=Standard1Pascal(Pa)=1Newtonm2(1Nm2)
Examplesofhowtousethetable1)Iftheairflowrateis85ft3minthemetricequivalent=85x000047=00399m3s2)Ifairpressureis150Patheimperialequivalent=150x0004=06inWaterGauge(WG)
Length inx2540 =mm mmx00394 =in inx00254 =m mx3937 =in ftx03048 =m mx32808 =ft
Area in2x6452 =mm2 mm2x000155 =in2
ft2x00929 =m2 m2x1076 =ft2
Volume ft3x00283 =m3 m3x353147 =ft3
Mass lbx04536 =kg kgx=22046 =lb cwtx50802 =kg kgx00197 =cwt tonx10162 =tonne tonnex09842 =ton
Density lbft3x160185 =kgm3 kgm3x00624 =lbft3
ft3tonx00279 =m3tonne m3tonnex3584 =ft3ton
Velocity ftminx00051 =ms msx1969 =ftmin
VolumeFlow ft3minx000047 =m3s m3sx2127 =ft3min ft3minx1699 =m3h m3hx05886 =ft3min
Pressure inWGx250 =Nm2(Pa) Nm2x0004 =inWG inWGx0250 =kNm2(kPa) kNm2x4 =inWG inWGx25 =mbar mbarx04 =inWG Atmosphere(STD)x1013 =bar barx0987 =Atmosphere(STD)
Flowrates lbhx04536 =kgh kghx22046 =lbh tonhx10162 =tonneh tonnehx09842 =tonh
Power hpx746 =W Wx00013 =hp
HeatFlow Btuhx0293 =W Wx3412 =Btuh
Heatenergycontent Btulbx0556 =kcalkg kcalkgx18 =Btulb
Moisturecontent grlbx000014 =kgkg kgkgx71420 =grlb
ThermalconductanceorThermaltransmittance Btuft2hdegFx5678 =Wm2˚C Wm2˚Cx0176 =Btuft2hdegF
Thermalconductivity Btuinft2hdegFx0144 =Wm˚C Wm˚Cx694 =Btuinft2hdegF
temperatureconversions
˚C -10 -9 -8 -7 -6 -5 -4 -3 -2
˚F 14 16 18 19 21 23 25 27 28
˚C -1 0 1 2 3 4 5 6 7
˚F 30 32 34 36 37 39 41 43 45
˚C 8 9 10 11 12 13 14 15 16
˚F 46 48 50 52 54 55 57 59 61
˚C 17 18 19 20 21 22 23 24 25
˚F 63 64 66 68 70 72 73 75 77
˚C=59x(˚F-32) ˚F=(95x˚C)+32Notetheconversionstabulatedareaccuratetoplusmn02˚CForgreateraccuracytheappropriateformulashouldbeused
otherconversionfactors
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
55S T O R E m a n a g E R S rsquo g U I D E
dewpointchartA4
Example1
bull Ifairrsquos(drybulb)temperatureis15˚Canditsrelativehumidityis70thedew-pointtemperatureofthatairis97˚C
Example2
Todeterminecondensationriskegbull Ifexternalairat8˚Cand84RHentersastorewillitcondenseonpotatoeswithatemperatureof5˚Cbull Checkdew-pointofairat8˚Cat84RHItis55˚Cbull Thereforetheairwillcondenseonanysurfacewithatemperaturebelow55˚Candsocondensationonthecrop willoccur
thedew-pointtemperatureofairbasedonitstemperatureandrelativehumidityUsethisdew-pointtabletodeterminecondensationrisk
(drybulb) relativehumidity() temperature (˚C) 60 62 64 66 68 70 72 76 80 84 88 92 96 100
20 121 126 131 136 140 145 149 157 165 173 180 187 194 200
19 112 117 122 126 131 135 139 148 155 163 170 177 184 190
18 103 107 112 117 121 125 130 138 146 153 160 167 174 180
17 93 98 103 107 112 116 120 128 136 143 150 157 164 170
16 84 88 93 97 102 106 110 118 126 133 140 147 154 160
15 74 79 83 88 92 97 101 109 116 124 131 137 144 150
14 65 69 74 78 83 87 91 99 107 114 121 127 134 140
13 55 60 64 69 73 77 81 89 97 104 111 117 124 130
12 46 50 55 59 63 68 72 80 87 94 101 108 114 120
11 36 41 45 50 54 58 62 70 77 84 91 98 104 110
10 27 31 36 40 44 48 52 60 67 75 81 88 94 100
9 17 22 26 30 35 39 43 50 58 65 71 78 84 90
8 08 12 17 21 25 29 33 41 48 55 62 68 74 80
7 -01 03 07 11 15 20 23 31 38 45 52 58 64 70
6 -10 -06 -02 02 06 10 14 21 28 35 42 48 54 60
5 -18 -14 -10 -07 -03 00 04 12 19 25 32 38 44 50
4 -27 -23 -19 -15 -12 -08 -05 02 09 16 22 28 34 40
3 -35 -31 -27 -24 -20 -17 -13 -07 -01 06 12 18 24 30
2 -43 -40 -36 -32 -29 -25 -22 -15 -09 -03 02 08 14 20
1 -52 -48 -44 -41 -37 -34 -30 -24 -18 -12 -07 -01 04 10
SourceCIBSE
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111
Potato CouncilSutton Bridge Crop Storage Research
East BankSutton Bridge
SpaldingPE12 9YD
Tel 01406 351444Fax 01406 351125
E-mail sbcsrpotatoahdborgukWeb wwwpotatoorguksbcsr
Free phone advice line 0800 02 82 111