NITROGEN FACTORS

AAFCO’s Laboratory Methods & Services Committee

Moisture Best Practices Working Group

July 31, 2018

Default6.25factor

100/16%N

Establishedinthe1880’s

baseduponpureproteinsreadilyavailableserumalbuminandglobulinfromblood

caseinfrommilk

Fewmatricescontainexactly16%Nintheirproteinstructure

D.B.Jones’sUSDACircular183in1931

establishedalisCngofnitrogen:proteinfactorsforavarietyofcerealgrains,oilseeds,nuts,andotherfoodcommodiCesImprovedtechnologiesandotherresearchershaveshownsomeoftheJonesfactorstobeinerror.

Soyprotein

5.71--Jonesstatedthatmajorproteininsoybeansisglycinin,

aglobulincomposedof17.5%N

glycininisonlyoneoftheproteinsinsoy

aminoaciddatagivefactorswithrangesof6.24–6.37

AOCS2013&2017

OfficialMethods&RecommendedPrac5ces

removedtablesoffactorsbecauseAOCSdoesnothaveinformaCononproteincomposiCon

TheposiConwasthattheuseofconversionfactorsshouldbeacontractualagreementbetweenbuyer

andseller,andnotascienCficone.

6.25forsoytrade

Aminoacidprofilesarenowmorefrequentlyusedtodetermineproteincontent.Tkachukconducted24,48&72-hourhydrolysisAmideNfromasparagineandglutamineMosseetalusedthesumoftheanhydrousaminoacidresiduestocalculateNfactorforeachaminoacidAnhydrousaminoacidresidue=eachaminoacidlosesonemoleculeofwaterwhentheyarejoinedtoformdipepCdelinkagesFAOrecommendedin2002tomeasureproteinasthesumofindividualanhydrousaminoacids

CorrecDonforNon-ProteinNitrogen

nucleicacids,amines,urea,biuret,ammoniumcompounds,nitrates,nitrites,vitamins,alkaloids,phospholipids,and

nitrogenousglycosides

Totheextentpossible,theNcontentofthesecompoundsneedstobesubtractedfromthe

totalNcontentwhenusingafactor

UseofMassBalancetoEvaluateAccuracyofProteinValuessumofH2O,protein,fat,ash&CHO=100(whereCHOisdeterminedfromNDF,sugars&starch)CaldwellatMidwestLabsobtainedproteinof100.1%using6.25factorondriedbeefstock.ProteinwasthencalculatedbysubtracConandvalueof90.75%obtained.Aminoacidanalysisshowedthatactualproteincontentwas90.35%.Factorshouldhavebeen5.64.

RECOMMENDATIONSUseAminoAcidAnalysistoDetermineProteinorNitrogen-ProteinConversionFactorCysteine/cysCne&methioninebyperformicacidoxidaContryptophanbybasehydrolysishydroxyprolineinmeatandcollagenproductsAnhydrousaminoacidresiduesaresummedtoesCmateproteinortocalculatetheconversionfactor.

RECOMMENDATIONSUseAppropriateNitrogen:ProteinFactorFAO&AOCS–6.25forsoyandvegetableproteinproductsDairyindustry–6.38fordairyproductsMilkreplacerifdairybaseduse6.38;ifsoybaseduse6.25Wheat–5.70Otherproducts–defaultfactorof6.25

RECOMMENDATIONS

UseCommonLogicDoesproteinvalueobtainedseemreasonableWasanynon-proteinnitrogenthatcanbedetermined(suchasureaandammonia)subtractedfromtotalNCalculatemassbalance(ifCHOareabsentorifNDF,sugars&starchweredetermined)=100Haveanotherindividuallookattheresultandatproduct

NON-PROTEINNITROGENandEQUIVALENTCRUDEPROTEINNfromurea,biuret,andammoniumsaltsaddedtoruminantfeediscollecCvelyknownasnon-proteinnitrogen(NPN).Manufacturersrequiredtolistequivalentcrudeprotein(ECP)contentonlabel.

ECP=NPNx6.25

NON-PROTEINNITROGENandEQUIVALENTCRUDEPROTEIN

NPN&ECPbothdeterminedbysamemethod.Confusioninhowresultsarereported.UreaseCtraConmethodmeasuresurea&ammoniumcompoundsasNH3andresultsareexpressedasN.ResultsfrommethodarereportedasNPN.NPNmustbymulCpliedby6.25toreportasECP.Thereisnofeedmethodtomeasurebiuret.

LawrenceNovotny(chair),reCredfromSouthDakotaStateUniversityOlsonBiochemistryLabsJaneCaldwell,MidwestLaboratories,OmahaNERichardCantrill,reCred,formerlyChiefScienceOfficer,AOCS(AmericanOilChemists’Society),Halifax,CanadaTeresaGrant,NorthCarolinaDept.ofAgriculture&ConsumerServices–Food,Feed&FerClizerSupervisorLarsReiman,Eurofins,MemphisTNNancyThiex,ThiexLaboratorySoluCons,BrookingsSDSharonWebb,UniversityofKentuckyRegulatoryServices

QuesCons?