united states protecting perishable foods...i protecting perishable foods during transport by truck...

United StatesDepartment ofAgriculture

AgriculturalMarketing Service

Transportation andMarketing Programs

HandbookNumber 669

September 1995

Reprinted July 2008

ProtectingPerishable FoodsDuring Transport by Truck

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Protecting Perishable Foods During Transport by Truckby B. Hunt Ashby

Agricultural Marketing ServiceTransportation and Marketing ProgramsSeptember 1995Reprinted July 2008

The U.S. Department of Agriculture (USDA) prohibits discrimi-nation in all its programs and activities on the basis of race,color, national origin, age, disability, and where applicable, sex,marital status, familial status, parental status, religion, sexualorientation, genetic information, political beliefs, reprisal, orbecause all or part of an individual’s income is derived from anypublic assistance program. (Not all prohibited bases apply to allprograms.) Persons with disabilities who require alternativemeans for communication of program information (Braille,large print, audiotape, etc.) should contact USDA’s TARGETCenter at (202) 720–2600 (voice and TDD).

To file a complaint of discrimination, write to USDA, Director,Office of Civil Rights, 1400 Independence Avenue, S.W., Wash-ington, D.C. 20250–9410, or call (800) 795–3272 (voice) or(202) 720–6382 (TDD). USDA is an equal opportunityprovider and employer.

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Contents

Introduction

I. Important Factors in Protection of Perishable FoodsRefrigeration ....................................................................................................................1Refrigeration Methods ....................................................................................................2

Mechanical Refrigeration ..........................................................................................2Ice ..............................................................................................................................3Cryogenic Refrigerants ..............................................................................................3

Trailer Design and Construction......................................................................................4Insulation ....................................................................................................................4Air Circulation Systems ............................................................................................4Multi-temperature Vehicles ........................................................................................6

Humidity ..........................................................................................................................7Precooling the Product ....................................................................................................8Freezing and Chilling Injury............................................................................................9Controlled and Modified Atmospheres..........................................................................11

II. Preparation for LoadingAdequacy of Equipment ................................................................................................13Cleaning and Sanitation ................................................................................................13Vehicle Maintenance......................................................................................................13Precooling or Prewarming of the Vehicle......................................................................16Preloading Checklist ......................................................................................................16

III. Loading ConsiderationsType of Air Delivery......................................................................................................17Type of Shipping Container ..........................................................................................17Whether Frozen or Nonfrozen ......................................................................................18Bracing Needs................................................................................................................18Compatibility of Mixed Loads ......................................................................................18Whether Palletized or Unitized......................................................................................19Length of Transit Period ................................................................................................19

IV. Loading and Load PatternsBasic Terminology ........................................................................................................20Loading Vehicles with Top-air Delivery........................................................................20

Hand-stacked Loads ................................................................................................20Unit Loads ................................................................................................................22

Loading Vehicles with Bottom-air Delivery..................................................................22Unit or Pallet Loads ......................................................................................................24Vented Loads..................................................................................................................24Top-iced Loads ..............................................................................................................24Loading Checklist ..........................................................................................................27

V. Individual Commodity RequirementsFresh Fruits and Vegetables ..........................................................................................28

Apples ......................................................................................................................28Apricots ....................................................................................................................29

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Artichokes ................................................................................................................29Asparagus ................................................................................................................29Avocados ..................................................................................................................30Bananas ....................................................................................................................30Beans (green, snap, or pole) ....................................................................................31Beans (lima, in pods)................................................................................................31Beets ........................................................................................................................31Beet Tops ..................................................................................................................32Blackberries ..............................................................................................................32Blueberries................................................................................................................32Broccoli ....................................................................................................................33Brussels Sprouts ......................................................................................................34Cabbage ....................................................................................................................34Cantaloupes ..............................................................................................................35Carrots ......................................................................................................................35Cauliflower ..............................................................................................................35Celery........................................................................................................................36Cherries ....................................................................................................................36Corn (sweet) ............................................................................................................37Cranberries................................................................................................................38Cucumbers ................................................................................................................38Eggplants ..................................................................................................................39Endive and Escarole ................................................................................................39Garlic (dry) ..............................................................................................................39Grapefruit..................................................................................................................40Grapes ......................................................................................................................40Kale ..........................................................................................................................41Kiwi Fruit ................................................................................................................41Lemons ....................................................................................................................42Lettuce (head) ..........................................................................................................42Lettuce (leaf) ............................................................................................................42Limes ........................................................................................................................43Mangoes....................................................................................................................43Melons (Honeydew, Casaba, Crenshaw, Persian) ....................................................43Mushrooms ..............................................................................................................44Okra ..........................................................................................................................44Onions (green), Shallots, and Leeks ........................................................................45Onions (dry bulbs)....................................................................................................45Oranges ....................................................................................................................45Parsley.......................................................................................................................46Parsnips ....................................................................................................................46Peaches and Nectarines ............................................................................................47Pears..........................................................................................................................47Peas (green and snow peas in pods) ........................................................................47Peppers (sweet) ........................................................................................................48Pineapples ................................................................................................................48Plums and Fresh Prunes ..........................................................................................48Potatoes ....................................................................................................................49Radishes....................................................................................................................50Raspberries ..............................................................................................................51Rhubarb ....................................................................................................................51Romaine Lettuce ......................................................................................................51Salad Mixes ..............................................................................................................52

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Spinach ......................................................................................................................52Squash and Pumpkins................................................................................................53Strawberries ..............................................................................................................53Sweet Potatoes ..........................................................................................................54Tangerines..................................................................................................................54Tomatoes (mature-green) ..........................................................................................54Tomatoes (pink) ........................................................................................................55Watermelons ..............................................................................................................55

Canned Foods................................................................................................................57Dairy Products ..............................................................................................................60

Butter and Margarine ................................................................................................60Cheeses ......................................................................................................................60Ice Cream ..................................................................................................................61

Fresh and Cured Meat and Fresh Seafood....................................................................62Boxed Meats..............................................................................................................62Carcass Meats............................................................................................................62

Frozen Foods ................................................................................................................66Poultry and Eggs ..........................................................................................................68

Poultry (fresh and hard-chilled) ................................................................................68Shell Eggs..................................................................................................................68

Appendix I........................................................................................................................71Estimating Mobile Refrigeration Requirements ..........................................................71Sample Refrigeration Requirement Calculation ..........................................................76

Appendix II ......................................................................................................................78Load Compatibility Groups ..........................................................................................78

Appendix III ....................................................................................................................83Recommended Protective Services for Perishable Foods During Transit....................83

Selected Bibliography......................................................................................................87

Other Resources ..............................................................................................................88

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List of Tables

Table 1. — Heat Absorption Characteristics of Certain Refrigeration Mediums

Table 2. — Sensitivity of Some Fruits and Vegetables to Freezing

Table 3. — Some Fruits and Vegetables Subject to Chilling Injury at Above-freezing Temperatures

Table 4. — Freezing Temperatures of Selected Canned Foods

Table 5. — Ideal Temperature Ranges for Transporting Common Types of Cheeses

Table 6. — Recommended Temperatures and Humidities for Protecting Selected Fresh,Cured, and Processed Meat and Seafood Products During Transit

Table I-1.— Specific Heat Above and Below Freezing for Certain Perishable Products

Table I-2.— Approximate Amount of Respiration Heat Produced by Certain Fruits and Vegetables at the Specific Temperatures

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List of Figures

1. Depletion of sucrose or sugar in sweet corn with increase in holding temperature.

2. Pathways of air in a trailer with a top-air delivery system.

3. Pathways of air in a trailer with a bottom-air delivery system.

4. Features essential for maintaining the critical airflow chain in trailers with top-air delivery.

5. Effect of different floor configurations on return-air space under the load.

6. A typical multi-temperature mechanically refrigerated trailer.

7. Methods of loading to reduce contact of products with walls and to reduce the chanceof freezing or chilling injury in extremely cold weather: (a) crosswise-offset stacking ofboxes or crates, (b) pyramid stacking of bagged products, and (c) center-loading of pal-letized loads.

8. Location of NPLA/RTF certification plates and decals which provide information on refrigeration rating and optional equipment on refrigerated trailers at time of manufacture.

9. Dimensional view of a load in a truck semi-trailer showing arrangements of containersin rows, stacks, and layers.

10. A typical airflow loading pattern for commodities packed in fiberboard boxes: (a) longitudinal view, (b) header stack, and (c) rear view of all other stacks.

11. Rear view of an airflow loading pattern modified for wirebound crates.

12. End and overhead views of basic pallet or unit load patterns in a semi-trailer: (a) airflow, (b) center-loaded, (c) wall-loaded, (d) off-set against walls, and (e) pin-wheel. (Note: Pallets used in pinwheel patterns must be 4-way or air flow under theload will be blocked.)

13. Effect of different unit load patterns on the percentage of cartons contacting the floorand walls in a typical load of a perishable product.

14. Example of strapping and corner boards on a unit load.

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15. Example of a method for bracing a load at the rear doors.

16. Rear view of a stacking pattern with horizontal wood stabilizing strips for top-icedloads in wirebound crates (shown) or waxed fiberboard boxes.

17. A palletized load of strawberries, center-loaded. (Note: Each pallet load is enclosed in an airtight plastic bag injected with a modified atmosphere.)

18. A mixed palletized load of celery and green onions loaded in a unit load airflow pattern.

19. Side (a) and end (b) views of a mixed load of hanging forequarters and hindquarters ofbeef.

20. A palletized load of eggs. Note the stretch film around the pallet loads at the rear doorarea where road shock is greatest.

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Preface

This is a revision of handbook No. 669 pub-lished in 1987. It superseded AgricultureHandbook No. 105, “Protecting PerishableFoods During Transport by Motortruck,”first published in 1956 and revised in 1970.These handbooks have been extremely pop-ular, and tens of thousands of copies havebeen distributed worldwide.

This updated edition reflects the dynamicchanges and innovations in the handling andtransportation of perishable foods. Some ofthese are the rapid change from hand-stacked loads to unitized loads on palletsand slipsheets, the use of microprocessorsfor more efficient refrigeration, and the useof satellites to monitor and control the per-formance of refrigerated vehicles duringtransit.

Many individuals and organizations provid-ed information or other assistance in revis-ing this handbook. Special recognition goesto W.L. Craig of USDA’s Agricultural Mar-keting Service for preparing the illustra-tions, and to L.A. Risse of USDA’s Agricul-tural Research Service for reviewing thispublication. A great deal of the informationon recommended holding requirements forfresh fruits and vegetables is from USDAHandbook No. 66 The Commercial Storageof Fruits, Vegetables, and Florist and Nurs-ery Stocks, cited in the bibliography.

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temperatures cause loss of vitamin C inasparagus, and sugar or sucrose depletion infresh sweet corn (figure 1). Low temperaturescan cause chilling injury to fresh fruits andvegetables. This may not show up until theproduct is at the retail store or on the con-sumer’s table, where failure to ripen properly,off-flavors, discoloration, pitting, and othersigns of poor quality may be evident.

Refrigeration removes excess heat and pro-vides temperature control for food products intransport vehicles. Heat is a positive and mea-surable form of energy that always radiates orflows toward the cold or refrigeration source.

In the United States, heat is measured inBritish thermal units (Btu). The Btu is definedas the amount of heat required to raise the

Refrigeration

The object of refrigerating food products isto maintain quality and prolong shelf life bykeeping the product temperature at the pointwhere metabolic and microbial deteriorationare minimized. Maintaining the desired orideal holding temperature is a major factorin protecting perishable foods against quali-ty loss during storage and distribution. Qual-ity loss is a function of both time and tem-perature abuse. Abuse is additive and, evenfor short periods of time during loading,transit, and unloading, may cause a consid-erable amount of quality loss by the time theproduct reaches its destination.

Abuse can result from temperatures that areeither too high or too low. For example, high

I. Important Factors in Protection of Perishable Foods

Figure 1. Depletion ofsucrose or sugar insweet corn with increasein holding temperature.

LOS

S I

N I

NIT

IAL

SU

CR

OS

E (

PE

RC

EN

T)

DAYS IN STORAGE

OoC(32oF)

1OoC(50oF)2OoC

(68oF)3OoC(86oF)

O 1 2 3 48O

O

60

40

20

temperature of 1 lb (0.45 kg) of water 1oF(0.56oC). A metric equivalent of the Btu isthe kilojoule (kj) or 1 Btu = 1.005 kj.

A truck refrigeration system must have suf-ficient capacity to remove heat generated bythe sources described below.

Residual heat from the air inside the trailer,and heat in the insulation and inner lining ofthe trailer.

Exterior heat conducted through the floor,walls, and ceiling. It is dependent on thetemperature differential between the insideand outside air, type and thickness of insula-tion, and the area of the conducting surfaces.Solar radiation will increase the temperatureof outside surfaces where the trailer body isexposed to the sun.

Infiltration heat from warm outside airthrough small holes, cracks, and door seals.It increases refrigeration requirements.

Excess heat in the commodity above thedesired transit temperature.

Heat of respiration generated by all freshfruits and vegetables. Some products, suchas asparagus, corn, and strawberries, respireat a higher rate than other products, such asapples, oranges, and potatoes. The rate atwhich respiration heat is generated alsovaries with the temperature of the product. Itis considerably less at temperatures nearfreezing than at normal harvest tempera-tures. Table I-1 in appendix I gives theamount of heat produced by various fruitsand vegetables at given temperatures.

Refrigeration Methods

In the past, several methods of refrigeratingtrucks have been used. These include ice, iceand salt, dry ice, hold-over plate systems,cryogenic systems, and mechanical refriger-ation. Today, however, mechanical refrigera-tion is the predominant type. Trailers refrig-erated with cryogenic refrigerants, usuallyliquid carbon dioxide (CO2) or nitrogen(N2), have been used to some extent over thepast three decades, but they are not as popu-lar as trailers refrigerated mechanically.

Mechanical RefrigerationMechanical refrigeration operates by absorb-ing heat at one point and dispensing it atanother. This is accomplished by circulatinga refrigerant between two points. The refrig-erant picks up heat through a coil (evapora-tor) inside the cargo space and discharges itthrough another coil (condenser) on the out-side. The refrigerant is circulated throughthe system by a compressor, which is drivenby a gasoline, diesel, or electrical motor.

On highway trailers most mechanical refrig-eration units are “nosemounted,” with theengine, condenser, and other accessories onthe outside front of the trailer, and the evap-orator coil and air fans directly inside.Refrigerated containers built for intermodalservice have the compressor engine and con-denser coil recessed flush with the outsidesurfaces in the front section of the contain-ers. This allows the containers to be evenlystacked aboard rail cars or containerships.

Mechanical refrigeration units are ratedaccording to their ability to remove or pro-duce heat. The cooling capacity of a unit isexpressed in the number of Btu’s per hour aunit can remove at 100oF (38oC) outside andat 35oF (1.7oC), 0oF (–18oC), and –20oF(–29oC) inside trailer temperature. Heatingcapacity of the unit is measured in Btu’s perhour, while inside trailer temperatures are65oF (18oC) or 35oF (1oC) under 0oF(–18oC) ambient. (The rating procedure isbased on the Air-Conditioning and Refrigera-tion Institute’s (ARI) Standard 1110.) Therefrigeration capacity needed for a particularload depends on the desired product temper-ature, the amount of vehicle insulation,ambient temperatures, product temperature atloading, amount of product respiration heat,and the extra capacity (reserve) desired.

Today’s refrigeration units are equipped withmicroprocessors programmed to control theoperation of the unit so that both refrigerationand fuel efficiency are maximized. Air tem-peratures are monitored at the discharge andreturn locations, and adjusted to demand forrefrigeration at the thermostat set-point. Thisreduces temperature spread around the ther-mostat set-point, which reduces dehydration

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and maintains product quality. The micro-processors also can be programmed to providediagnostic tests and automatically run througha pretripping mode. Some of the microproces-sors are radio-equipped and may be contactedvia satellite to monitor performance of therefrigeration unit, pinpoint geographic loca-tion of the trailer, monitor product tempera-tures, and perform other functions.

IceIce is a good absorber of heat (table 1) andalso helps to maintain humidity in loads offresh produce. The main drawbacks for iceare its weight, which cuts down on the pay-load; the difficulty and expense of replenish-ing ice enroute; the need for water-resistantpackaging when applied as top-ice; and thedamage some fresh fruit and vegetablesincur when contacted by ice.

Crushed or slush-ice blown over the top ofproduce loads is used to refrigerate and main-tain high levels of humidity for certain prod-ucts. This is known as “top-icing.” Someshippers may apply the crushed ice or slush-ice to individual pallet loads or in individualboxes of product (package-ice) before loading.

Cryogenic RefrigerantsCryogenic (low-temperature) refrigeratingsystems, which use liquid or solid carbon

dioxide (CO2) or liquid nitrogen (N2), areavailable for highway trailers. They are usedprimarily in delivery operations requiring 1-day or less transit time, since supplies ofliquid cryogens are not available at truckstops. Advantages of the cryogenic systemsare that they have fewer moving parts tomaintain and replace, and also allow quickrecovery of thermostat set-point temperatureafter delivery stops.

Liquid cryogenic systems usually operate byhaving the liquid refrigerant in pressurizedtanks. A temperature-sensing element insidethe trailer activates a controller whichreleases the liquid refrigerant through aspray nozzle at the ceiling of the trailer. Theliquid CO2 or N2 spray flashes into gas as ithits the warmer air in the trailer, absorbingthe heat. When the desired temperature isreached, the sensing element sends a signalto the controller to shut off the flow ofrefrigerant. In another type system, the liq-uid CO2 is circulated through a coil or plateheat exchanger and the vaporized gas ventedoutside. A third type of system stores CO2

snow in a full length ceiling bunker andcools as the snow melts.

WARNING: Allow adequate time forreplenishment of oxygen before entering avehicle refrigerated by CO2 or N2. Workers

Table 1. Heat Absorption Characteristics of Various Refrigeration Mediums

Amount of Heat Absorbed At or

Medium Above Freezing1 Below Freezing

Btu’s/lb Btu’s/lbIce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

Carbon Dioxide (CO2)Liquid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 120Solid (dry ice) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240

Nitrogen (N2)Liquid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 165

1 Freezing = 32oF (0oC)

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entering a vehicle with concentrations ofCO2 or N2 gases may be rendered uncon-scious by the lack of oxygen.

Also, high concentrations of cryogenicrefrigerant gases (generally above 20 per-cent) may have an adverse effect on freshproduce. Most fresh fruits and vegetableswill eventually suffocate in a 100-percent N2

atmosphere, although many products willtolerate high levels of N2 for a few dayswithout injury. High percentages of CO2 gasin the atmosphere may cause off-flavors,off-colors, and physiological disorders infresh produce. On the other hand, moderateconcentrations of this gas are successfullyused to retard decay and ripening of fruitsand vegetables during transit and storage.Generally, N2 atmospheres are not harmfulto food products, and CO2 atmospheres helpretard microbial growth on fresh meat andmeat products (see “Controlled and Modi-fied Atmospheres”). Neither CO2 nor N2 gaswill harm frozen foods.

Solid CO2 (dry ice) may be in the form ofblocks, snow, or pellets, all of which areused as refrigeration mediums in transportvehicles. The most frequent use of solid CO2

is in frozen food and ice cream deliverytrucks. Solid CO2 may be used as an emer-gency refrigerant in the event of mechanicalunit breakdown in vehicles hauling frozenproducts. Dry ice changes into gas at–109oF (–78.3oC). Table 1 gives the heatabsorption characteristics of these mediums.

Trailer Design and Construction

InsulationVehicles used to transport perishable foodproducts should be well insulated to retardthe flow of heat through their walls. Insulat-ing quality is measurable, and the industrystandard is the U factor (coefficient of heattransfer through a trailer body). The lowerthe U factor, the better the insulation.

Plastic foams are the predominant materialused in insulating refrigerated vehicles becausethey offer a low U factor, are lightweight,waterproof, and noncorrosive. Additional insu-lation advantages are obtained when the plastic

is “foamed in place” during manufacture. Thisprocedure fills in cracks and crevices thatwould otherwise allow air leakage.

Insulation quality is further enhanced by theuse of highly polished steel or aluminumexterior skin which reflects heat rays fromthe sun or road surfaces. There also arereflective paints for refrigerated vehicles.The reflecting effect of any material isdiminished, however, if the outside of thevehicle is not kept clean.

High-quality insulation will be of little valueif door seals are leaking. Door seals must beproperly fitted and in good repair.

Air Circulation SystemsAir circulation is one of the most importantfactors in protecting refrigerated loads ofperishable foods. Refrigeration capabilitiesare meaningless if the refrigerated air is notproperly circulated to maintain producttemperature.

Air circulation carries product heat and theheat which penetrates the walls, floors, andceiling of the trailer to the refrigeration unitwhere it can be removed. Heated air may becirculated to keep fresh produce from incur-ring chilling or freezing injury. Air circula-tion also is important to ensure uniform tem-peratures throughout the load.

There are two major methods of circulatingair in refrigerated vehicles. Overhead, ortop-air, delivery is the conventional method.The second method is bottom-air delivery,which has been employed extensively inseagoing van containers for several decades,but only to a limited extent in highway trail-ers. Figures 2 and 3 illustrate the pathwaysof airflow in top- and bottom-air deliverytrailers respectively.

Top-air delivery In trailers with top-air delivery, air circula-tion and subsequent control of load tempera-tures are enhanced by the construction fea-tures below.

Ceiling ducts to direct the air from theblower to the rear of the trailer. The Nation-

al Perishable Logistics Association/ Refrig-erated Transportation Foundation(NPLA/RTF), a non-profit association ofrefrigeration equipment manufacturers andusers, recommends that the air deliverychute provide a minimum of 240 squareinches (1548 cm2) of cross-sectional areafrom the front of the vehicle to 10 to 15 feet(3 to 5 m) from the rear. Progressive air spillprovisions should be provided (except in thefront 10 feet (3 m) of length. A maximum load height lineshould be painted on the walls below thelevel of the bottom of the air delivery chute.Figure 4 illustrates features considered criti-cal for maintaining the airflow pathways ina loaded refrigerated trailer.

Vertical channels or ribs on the inside ofthe rear doors and provisions for cross brac-ing at the rear of the load to prevent theblocking of air circulation between the loadand the rear doors in the event of load shift.

High airflow floors that allow air to circu-late under the load. About 240 square inches(1,548 cm2) of return air passage are neededfor the average trailer’s refrigeration fan tooperate at 100 percent capacity. Figure 5shows the effect of different floor configura-tions on return air space. The product shouldbe loaded on pallets or floor racks whenspace for air circulation under the load isinadequate due to floor design.

Figure 2. Pathways of air in atrailer with a top-airdelivery system.

CONDENSER

HEADERSTACK

BULKHEAD WALL

RETURN AIR

FAN

DISCHARGE AIREVAPORATOR

Figure 3. Pathways of air in atrailer with a bottom-airdelivery system.

CONDENSER

T–RAIL FLOORFLOOR COVERIN OPEN SPACE

DISCHARGE

FAN

RETURNEVAPORATOR

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Ribbed sidewalls or spacers at least 1 inchthick (3 cm) to allow top airflow down thesides of the load. This reduces the amount ofheat conducted across the walls to or fromthe product. Up to 20 percent of the top air-flow should bleed off down the sidewalls.

A solid-front bulkhead designed to allow airfree return to the refrigeration unit. If the airis blocked, the fan will turn, but not blowair. The NPLA/RTF recommends that thebulkhead be positioned a minimum of 3inches (8 cm) from the front wall. A mini-mum of 6 inches (15 cm) of open spaceshould be left between the bottom of thefloor and the bottom edge of the bulkhead.The top side of the bulkhead should have 30to 50 square inches (196 to 323 cm2) ofopen area to allow mixing of top and bottomair, and to allow some return air to the ther-mostat should the airflow be interrupted byimproper loading or load shift. Bumpers orvertical strips should be attached to the open

area at the bottom of the bulkhead wall toprevent the load from blocking air return tothe blower under the bulkhead.

Bottom-air deliveryA few refrigerated highway trailers andmost van containers used in overseas tradeare equipped with bottom-air type delivery.In this type system, air is forced under andup through the load at a rate of 3,000 to5,000 cubic feet per minute (85 to 142cubic meters per second) and a static pres-sure of 1.5 to 3 inches (0.37 to 0.73 kPa)water. (The abbreviation kPa stands forkilopascal, a metric unit used to measurepressure.) The air returns to the refrigera-tion unit over the top of the load andthrough the top of the bulkhead (figure 3).

Multi-temperature VehiclesWithin the last decade there has been a rapidgrowth in the use of multi-temperature trail-ers for food delivery operations, especially

Figure 4. Features essential formaintaining the criticalairflow chain in trailerswith top-air delivery.

ADEQUATEHEAD SPACE

WALL CHANNELS

RETURN AIRBULKHEAD

DEEP FLOOR CHANNELS

REARDOORCHANNELS

AIR CHUTE

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for fast food and independent grocery stores.Multi-temperature vehicles usually havethree compartments separately controlled at0oF (–18oC) or below for frozen foods,around 35oF (2oC) for chilled foods, andaround 55oF (13oC) for chill-sensitive prod-ucts (figure 6).

Liquid CO2 refrigeration systems are used insome delivery operations. A major advan-tage of these systems is fast temperaturerecovery after door openings. This is partic-ularly important for protecting the quality offrozen foods in warm weather where cumu-lative door opening time may be one ormore hours. The injection of liquid CO2 intothe compartments after a door opening pro-vides almost instantaneous recovery to thethermostat set-point.

Mechanically refrigerated vehicles have aseparate coil in each compartment. Each coiloperates from a single refrigeration unit atan independent temperature set-point .

Humidity

The proper humidity or moisture content of

the air surrounding fresh fruit and vegeta-bles helps maintain quality during transport.Most perishable horticultural productsrequire high relative humidities of 85 to 95percent to prevent dehydration and to keepthem fresh and crisp.

Relative humidity, as used in this text, is thepercentage of water vapor in the air in rela-tion to the saturation point of the air at agiven temperature.

In mechanically refrigerated vehicles, mois-ture is continually evaporated from the prod-uct and condensed from the circulating airby the refrigeration coil. Some productmoisture loss during transit must be accept-ed, but it can be minimized by the followingpractices:

• using top- or package-ice where possible;

• precooling thoroughly to reduce the tem-perature differential between the productand the surrounding air;

• keeping the refrigeration coil only a fewdegrees colder than the desired transittemperature;

Figure 5. Effect of different floorconfigurations on return-air space under the load.

T–RAIL FLOOR

198 SQ. INCHES

325 Sq. Inches45 Sq. Inches

1 1/4"

3 1/2"

1 1/4"

2 1/4"

DUCT BOARD FLOOR& PALLET

DUCT BOARD FLOOR

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• waxing the product or using semi-perme-able wraps to reduce evaporation; and

• installing a humidity control system.

Precooling the Product

To maintain a fresh appearance, preventdecay, and extend the market life of mostfresh fruits and vegetables, it is necessary tostart lowering the temperature and removingthe field heat from the product as soon afterharvest as possible. Any cooling completedbefore the product is shipped is referred toby the industry as precooling. Precoolingmay include one or a combination of the fol-lowing methods:

• refrigerated forced air;• vacuum cooling;

• hydrocooling; and

• slush- or package-ice.

Some fresh fruits, vegetables, and carcassmeats are shipped before they have been pre-cooled to the proper transit temperature. Theideal situation would be for the carrier toaccept only properly precooled product. Whenthis is not practical, the trailer’s refrigerationsystem must bear the additional heat load.

Most truck refrigeration units have enoughreserve capacity to remove a reasonableamount of heat in addition to respiration heatand heat transferring through the vehicle

Figure 6. A typical multi-temperaturemechanically refrigeratedtrailer.

Photo courtesy of Carrier-Transi-

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body. However, if the product is much abovethe desired transit temperature at loadingtime, the entire heat load should be estimated(see appendix I). If the estimated heat load ismore than the refrigeration unit is rated tobear, the trailer should not be used.

Freezing and Chilling Injury

Trucks transporting perishables throughareas with outside temperatures much lowerthan 32oF (0oC) may need to be warmedrather than refrigerated to prevent freezingor chilling injury. Product freezing also mayoccur if the thermostat setting is too low,particularly on the top layer where air exitsthe refrigeration unit discharge chute.

Freezing fresh meat will darken its color andincrease thaw drip. Eggs may crack andincur irreversible physical changes by freez-ing. The texture of some cheeses arechanged by freezing.

Freezing losses are most common in fruitsand vegetables such as apples, celery, andlettuce which normally move at tempera-tures near their freezing point. The extent ofinjury varies with the characteristics of theproduct and the severity of freezing. Com-modities such as beets and cabbage canwithstand light freezing and thawing severaltimes without permanent injury. Other prod-ucts such as potatoes and tomatoes are per-manently injured by only one slight freez-ing. Table 2 groups certain commodities bytheir sensitivity to freezing injury.

Some fresh fruits and vegetables are subjectto low temperature or chilling injury at tem-peratures above 32oF (0oC). Symptoms maybe pitting, discoloration, off-flavors, physio-logical deterioration, and increased decay.Chilling injury varies with both time andtemperature. Some commodities, such asbananas, will be injured by a few hours’

Table 2. Sensitivity of Some Fruits and Vegetables to Freezing

Most sensitive1 Moderately sensitive2 Least sensitive3

Apricots Apples BeetsAsparagus Broccoli, sprouting Brussels sproutsAvocados Cabbage, new Cabbage, oldBananas Carrots DatesBeans, snap Cauliflower KaleBerries4 Celery KohlrabiCucumbers Cranberries ParsnipsEggplants Grapefruit RutabagasLemons Grapes SalsifyLettuce Onions, dry TurnipsLimes OrangesOkra ParsleyPeaches PearsPeppers, sweet PeasPlums RadishesPotatoes SpinachSquash, summer Squash, winterSweet potatoesTomatoes

1 Commodities likely to suffer injury by one light freezing.2 Commodities able to recover from one or two light freezings.3 Commodities that can be lightly frozen several times without sustaining serious damage. 4 Except cranberries.

10

exposure to chilling temperatures. Otherscan be held below the desired storage tem-perature for several days before incurring

serious injury. Table 3 lists some of themajor fresh produce susceptible to chillinginjury when held below recommended tem-peratures during transit or storage.

Table 3. Some Fruits and Vegetables Subject to Chilling Injury at Above-freezing Temperatures

Approximate lowest Commodity safe temperature1

oF oC Avocados:

Cold-tolerant varieties . . . . . . . . . . . . . . . . . . . . . . . . . 40 4.4Cold-intolerant varieties(West Indies) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 12.8

Bananas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 12.8Beans (snap) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 7.2Cucumbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 7.2Eggplants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 7.2Grapefruit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 10.0Lemons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 10.0Limes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 7.5Mangoes:

Irwin and Zill varieties . . . . . . . . . . . . . . . . . . . . . . . . . 50 10.0Haden and Keitt varieties . . . . . . . . . . . . . . . . . . . . . . . 55 12.8

Melons:Cantaloupes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 2.2Honeydew, Casaba, Crenshaw,

and Persian . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 7.2Watermelons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 4.4

Okra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 7.2Oranges (California and Arizona

grown) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 3.3Papayas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 7.2Peppers (sweet) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 7.2Pineapples:

Mature-green . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 10.0Ripe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 7.2

Potatoes:Table stock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 3.3Chipping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 10.0

Pumpkins and hardshell squashes . . . . . . . . . . . . . . . . . . 50 10.0Sweet potatoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 12.8Tomatoes:

Mature-green . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 12.8Pink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 7.2

1 Based on maximum transit time of 5 days; however, chilling injury may vary considerably by cultivar, harvest sea-son, holding time, maturity of commodity, etc.

11

Since heat moves toward the cold source,during very cold weather the heat fromproduct loaded against the walls and floor ina truck will move outward. The best meth-ods of preventing this heat loss and subse-quent freezing or chilling damage are:

• reducing the amount of surface contact ofthe product with the floor and walls; and

• circulating warmed interior air around theperimeter of the load.

Various loading methods may be used toreduce product contact with the walls andfloor. For example, the offset-by-layers load-ing pattern reduces box contact with the wallsby about 50 percent and also provides ductsfor warm air to circulate along the length ofthe wall (figure 7a). Hand-stacked loads ofbagged products can be pyramid stacked (fig-ure 7b). Palletized loads should be center-loaded away from the walls (figure 7c).

Enhance perimeter air circulation by usinghigh airflow or deep T-rail floors (figure 5).If the vehicle is not equipped with deep-channeled floors, use pallets or disposablewooden floor racks to prevent contact of theproduct and floor and for more space for thewarmed air to circulate under the load.Ribbed or vertically grooved walls will allowincreased air circulation down the walls andreduce surface contact with the product.

Controlled and Modified Atmospheres

The practice of using controlled or modifiedatmospheres as a supplement to refrigerationis increasing. Such atmospheres areachieved by altering the normal atmospherein the vehicle with varying concentrations ofone or more gases, usually oxygen (O2), car-bon dioxide (CO2), and nitrogen (N2).

A controlled atmosphere (CA) is attainedwhen concentrations of gases making up theatmosphere in a vehicle are constantly replen-ished to maintain predetermined levels. Inmodified atmospheres (MA), gas concentra-tions are initially modified to meet specificproduct criteria, but not consistently replen-ished in transit to maintain the initial levels.

Nearly every product, and sometimes eachvariety, has a different combination of gasesin which it keeps best during storage. Anatmosphere that improves the keeping quali-ties of one product may have an adverseeffect on another. Temperature and humiditymodify the effects of controlled atmospheres.For these reasons, consult appendix II of thishandbook and information on individualcommodities in the USDA Handbook No. 66(see Selected Bibliography) before applyinga modified atmosphere to a product load.

Strawberries are the product most common-ly shipped in a modified atmosphere. CO2

gas is a basic component in atmospheres forberry and cherry shipments because it is amold retardant. N2 gas usually is a basiccomponent for green leafy produce sinceCO2 gas may cause discoloration of theseproducts. Reducing O2 levels retards ripen-ing and decay that take place in normal air.Extremely high or disproportionate levels ofany gas may result in product discolorationand off-flavors.

Sealing the trailer tightly enough to hold thedesired concentrations of gases during tran-sit is a major problem in truck shipments. Amore common practice is to load the trailer,apply a plastic film curtain sealed aroundthe inside of the rear doorway, evacuate theair through port valves, and then inject thedesired atmosphere. In some cases, a largeplastic bag enclosing the entire cargo spaceis inserted in the trailer, the product isloaded inside the bag, the bag is sealed andthe desired atmosphere is injected. For tran-sit periods of more than several days, vehi-cles containing a modified atmosphereshould be recharged with gas enroute.

For both truckload and less than truckloadlots, individual pallet loads of the productare sealed in plastic bags, the air evacuated,and a modified atmosphere injected. Thepreparation of vehicles or pallet loads forMA shipments is usually done by companiesspecializing in this trade. They also marketthe applicable gases, usually under a regis-tered trademark. In some cases they provideservices for monitoring and recharging theatmospheres in transit.

12

Figure 7.Methods of loading toreduce contact ofproducts with walls andto reduce the chance offreezing or chilling injuryin extremely coldweather: (a) crosswise-offset stacking of boxesor crates, (b) pyramidstacking of baggedproducts, and (c) center-loading of palletizedloads.

(A) CROSSWISE - OFFSET STACK (B) PYRAMID STACK

(C) CENTER - LOADED

13

Preparation for loading is an important step inputting together a successful shipment. Whendeveloping and implementing a good preload-ing plan, consider the following factors:

Adequacy of Equipment

The truck’s refrigeration system should beoperating properly and have the capacity tomaintain the proper temperature of theintended product load. If the vehicle isNPLA/RTF certified, the refrigeration unitand insulation rating can be found on perfor-mance plates or decals attached at variouslocations (see figure 8). These decals alsoprovide information on optional equipmenton the trailer which affects refrigeration per-formance, such as bulkheads, air chutes, etc.

Cleaning and Sanitation

Clean and sanitize the vehicle. Cleanlinessprevents bacterial, chemical, and odor conta-mination of food product loads. Remove allloose debris and wash or sweep the floorsclean. The floor drains and grooves shouldbe free of debris so drainage will not beblocked.

Certain cleaning procedures may be requiredby law in cases where a meat product maybecome contaminated by direct or indirectcontact with the interior surfaces of thevehicle. Also, certain cleaning laws mayapply due to previously hauled cargo, suchas chemical residues or municipal wastes.(See also section VI, “Regulatory Consider-ations for Truck Construction Materials,Cleaning Compounds, and Sanitation.”)

Fatty or oily food products, such as butter,oleomargarine, and meats, are highly sus-ceptible to contamination by strong odors.Fresh fruit, such as apples and bananas, alsoeasily absorb strong odors. Thorough clean-ing and airing of vehicles previously used

for hauling fish, cabbage, and other odorousproducts are necessary. Leaving freshlyopened cans of ground coffee for 8 or morehours in a closed vehicle may be helpful inabsorbing odors. The grounds may be spreadover the floor and then swept clean beforeloading. Truckers should refrain from trans-porting products leaving strong residualodors if they plan to haul fresh meats orother odor-absorbing products soon after.

Vehicle Maintenance

Properly maintain vehicles. A regular main-tenance program that keeps a refrigeratedtruck in good repair improves its ability tomaintain desired product temperatures dur-ing transit. In the long run, maintenance andrepairs are less costly than claims and lostrevenue from delivery of products in poorcondition.

Rough or splintered sidewalls and protrud-ing nails or screws can tear containers anddamage the commodity. Cracked wall linersprovide lodging points for dirt and old foodparticles which encourage microbial andinsect infestation. Walls punctured by fork-lifts or broken at the seams allow moistureto penetrate the insulation and reduce itseffectiveness.

Check door seals and floor drain caps regu-larly and repair or replace as needed. Themashed-end rubber caps on floor drains tendto clog with debris, and wash crews some-times cut them off. All seals should be main-tained. Dirt and air are sucked into openspaces left by worn and missing seals anddrain caps. This adds to refrigeration loadsand product contamination.

Keep air chutes or ducts in place and free ofholes. The ducts are designed to distributeair so that the load is uniformly cooled.Defective or missing ducts will result in air

II. Preparation for Loading

Figure 8. Location of NPLA/RTF certification plates and decals which provide information on refrigeration rating and optional equipment on refrigerated trailers at time of manufacture.

14

(TEMPERATURE CONTROL UNIT MANUFACTURER’S NAME)

TEMPERATURE CONTROL UNIT PERFORMANCECooling Heating Air Discharge

(100oF) Ambient (0oF Ambient)35oF___Btu/hr 65oF___Btu/hr No Load____CFM0oF___Btu/hr 35oF___Btu/hr System Load____CFM

–20oF___Btu/hr

MODEL ______________________Tested in accordance with the Refrigerated TransportationFoundation.Recommended Practice No. ___________. (latest revision)

2 HEAT TRANSFERCHARACTERISTICS

(VEHICLE MANUFACTURER’S NAME)

THERMAL PERFORMANCEThis structure is certified in accordance with Truck TrailerManufactuers Association Recommended Practice No. 38 –(latest revision) and Refrigerated Transportation FoundationMethod for Classification, Recommended PracticeNo.________________________________(latest revision)V.I.N. __________________________________________Date of Certification _______________________________Heat Transmission Rate __________________BTU/hr –oFFloor Airflow Area ______________________________in2

Side Lining Airflow Area ________________________in2/ftof vehicle length

Rear Door Airflow Area __________________________in2

1 REFRIGERATION CAPACITY

3 COMBINEDEQUIPMENTIDENTIFICATION

REFRIGERATED TRANSPORTATION FOUNDA-TION

EQUIPMENT CLASSIFIEDBY: _______________________________________DATE OF CLASSIFICATION:___________________TRAILER V.I.N.: _____________________________TEMPERATURE CONTROLUNIT MODEL NUMBER: ______________________

Vehicle Bulkhead Chute Floor Door SideRating Lining Lining

15

VEHICLESPECIFICATIONS CODEBulkheadSolid (pressure) SLattice LNone NAir Delivery SystemYes YNone NFloorHigh HMedium MLow LFlat FRear DoorsHigh HMedium MLow LFlat FSidewallsNon-flat (Ribbed) RFlat F

QUALITY PRODUCT PROTECTIONVehicle Ratings Type of Product ProtectionC65 = 65F Controlled TemperatureC35 = 35F Fresh Fruit and VegetablesF = 0F Frozen FoodsDF = –20F Ice Cream & Frozen Foods

s

s

16

short-circuiting back to the refrigeration unitover the top of the load. This often causesfreezing on the top layer and hot spots in thelower layers.

Precooling or Prewarming of the Vehicle

Precool or prewarm the vehicle to thedesired transit temperature for the intendedproduct load. During hot weather, precool-ing reduces the chance of overloading therefrigeration system. It also prevents furtherwarming or thawing of the product fromheat in the walls and floor. A number ofvariables, such as ambient temperatures,refrigeration unit capacities, and insulation,make it hard to have a set procedure for pre-cooling. A recommended procedure is to setthe thermostat at the desired temperature,close the doors of the vehicle, and run therefrigeration unit until the heat transferthrough the vehicle body is stabilized at thethermostat set-point. This may take 2 ormore hours in hot summer weather. Some ofthe newer refrigeration units are equippedwith micro-processors with an automaticprecooling cycle function. Still, scheduleadequate time for precooling.

CAUTION: Shut the refrigeration unit offwhen loading from an open dock. Leavingthe doors open may result in ice forming onthe refrigeration coil, blocking refrigeratedair circulation during transport.

During extreme subfreezing weather, pre-warm the interior of the vehicle before load-

ing commodities such as fresh onions orpotatoes. Most vehicles are equipped with aheating cycle on the refrigeration unit. Oper-ate the unit on the heat cycle far enough inadvance of loading to stabilize the interiorair and body temperature of the trailer at thedesired transit temperature of the product.

Preloading Checklist

The following is a suggested preloadingchecklist:

( ) Refrigeration unit operating properly?

( ) Thermostat calibrated?

( ) Refrigeration air chutes or ducts properlyinstalled and in good repair?

( ) Door seals in good condition?

( ) Doors seal tightly when closed?

( ) Walls free of cracks or holes?

( ) Front bulkhead installed?

( ) Floor drains open?

( ) Inside of the vehicle clean and odor free?

( ) Floor grooves free of debris?

( ) Inside length, height, and width adequatefor the load?

( ) Load locks or other devices available tosecure load?

( ) Is the trailer or container precooled orprewarmed?

17

The packaging, handling, and trailer equip-ment for perishable foods varies consider-ably, and this complicates loading decisionsfor truck drivers. Consider the followingfactors, along with the kind of equipmentavailable, when planning a load.

Type of Air Delivery

Currently there two types of air delivery systems available on refrigerated trailers andcontainers. Each system requires differentloading procedures for both hand-stackedand palletized loads to maximize coolingefficiency and maintain temperature control.

Top-air delivery is the conventional systemused in refrigerated trailers (see figure 2).With this system, high velocity, but lowpressure, air exits the refrigeration unit atthe front ceiling, travels over the top of theload, down between the end of the load andrear doors, and under and through the loadto return to the refrigeration unit at thefront of the vehicle. When loading a top-airvehicle, keep pathways open for airflowback to the refrigeration unit. For respiringproduce, air pathways also are neededthrough the load interior for removal ofrespiration heat.

Bottom-air delivery systems are used mainlyon intermodal van containers for exportshipments. In bottom-air systems, refrigerat-ed air is forced down the front bulkhead andunder the load through a T-rail floor, andthen vertically up through the load (see fig-ure 3). A high static pressure is maintainedunder the load to assure a low velocity butsteady movement of air through small open-ings in the load. Load a bottom-air vehicletightly over the floor area, and cover anyopen space on the floor not covered by theload to maintain the air pressure under theload.

Type of Shipping Container

Load shipping containers in a manner thattakes maximum advantage of their inherentstrength. Different containers are stackedand handled in varying ways because oftheir design, the way they are packed, andthe material from which they are made.Most containers are designed to withstandmore pressure or weight on one side or areawithout collapse or damage to the contents.Certain types of “packs” tend to leave abulge on one or more faces of the container.If at all possible, do not load bulged contain-ers with pressure on the bulging faces.Wooden wirebound crates used for corn arean example of this type pack. Load thesecontainers on their sides to prevent crushingof the contents under the bulge.

Wooden boxes, lugs, and wirebound cratesare designed to bear weight on the endsonly. The tops, bottoms, and sides usuallyare made up of thin slats which serve onlyto keep the product within the container.Stack these containers directly on each otherso that the overhead weight is borne by theends of the crate, or the contents may beseverely crushed and bruised.

Corrugated fiberboard boxes are designed tobear vertical overhead weight on their fourwalls. Load fiberboard boxes upright ontheir bottoms and stack evenly on top ofeach other. The four corners are the strong-est points. Avoid cross-stacking whereexcessive pressure put on the boxes at mid-section may cause product damage. Boxesmay usually be cross-stacked on the toplayer.

Wooden baskets and hampers are designedto withstand overhead weight bearing verti-cally on their tops or bottoms. Fasten thecover lids securely at all fastening points sothat the lid bows slightly. The bow distrib-

III. Loading Considerations

18

utes overhead weight evenly to the sides ofthe basket rather than letting it bear directlyon the produce under the cover.

Bulk and bagged commodities are highlysusceptible to bruising from overheadweight, especially when loaded on groovedor rough floors. Commercial cushioningmaterials, such as paper and plastic foampads, will provide some protection for theseproducts. Fiberboard slipsheets also may beused for floor cushioning. Any cushioningmaterial should be perforated for air circula-tion. Do not use materials, such as straw,that will block air circulation under the load.

During cold weather, floor cushioning mate-rial also serves as insulation to preventfreezing damage at the point it is most likelyto occur. However, the most effectivemethod of preventing freezing of the prod-uct at floor level is to circulate warmed airunder the load. In vehicles not equippedwith high airflow floors, raise the load onpallets or floor racks to get adequate air cir-culation under the load.

Whether Frozen or Nonfrozen

Load frozen foods that have been cooled tothe desired 0oF (–18oC) or below transittemperature in a different manner from freshrespiring produce. Load boxes of frozenfood tightly together with as little contactwith the vehicle floor and walls as possible.The goal is to have cold air circulatingaround the load perimeter to intercept heatradiating through the body of the trailerbefore it reaches the frozen cargo. (See alsothe section “Frozen Foods.”)

Bracing Needs

Bracing prevents the load from shifting andblocking air circulation channels and/orcausing physical damage to the product. It isespecially important to secure containers inthe top layers toward the rear of the load.Here they are highly susceptible to bouncingand toppling, and subsequent bruise andabrasion damage from shock and vibrationtransmitted from the road bed.

Prevent the accumulation of lengthwiseslack space during loading. Use cross-brac-ing at the end of the last stack to prevent thecargo from shifting backward and blockingair circulation at the rear doors. This is par-ticularly important in loads for piggybackrail (TOFC) shipments, where the vehiclesmay be loaded so they are moving back-wards. If the load is a split shipment or amultiple drop-off (one that is consigned toseveral receivers), use cross-bracing at theend of the last stack left after each drop-offto keep the cargo in place until the next stopis reached. Use air bags, spacer blocks, andload lock bars to secure palletized loads.

Compatibility of Mixed Loads

Many truck shipments contain two or moredifferent food products. Consider fiveimportant factors in determining the compat-ibility of products in mixed loads:

(1) required commodity temperature,

(2) required relative humidity,

(3) emission of physiologically active gasessuch as ethylene,

(4) odor-absorbing characteristics, and

(5) modified atmosphere requirements.

The desired transit temperature of productsshipped together should be within reason-ably close range. For example, mature greentomatoes requiring a transit temperature of55oF (13oC) should not be shipped in com-bination with lettuce needing a transit tem-perature of 32oF (0oC).

The relative humidity requirements of mixedproducts should be reasonably close. Someproducts may be shipped in contact with iceand saturated by melt water. Other productsmay be injured by contact with ice or watersaturation.

Certain fruits and vegetables produce ethyl-ene gas during respiration. Ethylene maybring about premature ripening or it maydamage carrots, lettuce, most flowers, andsome nursery stock. Fruits and vegetables

19

producing significant quantities of ethyleneare apples, avocados, bananas, cantaloupes,honeydew melons, peaches, pears, plums,and tomatoes. Commodities that shouldretain a green color during transit, such asbananas, cucumbers, and peppers, shouldnot be shipped in combination with heavyethylene producers. Ethylene production isless pronounced at temperatures near freez-ing than at higher temperatures. Exchangingthe air in the vehicle periodically by openingvent doors will help reduce ethylenebuildup. Ethylene scrubbers also are avail-able commercially.

Take care not to mix shipments of odor-pro-ducing products with odor absorbers. Odorsgiven off by apples, citrus, onions, pineap-ples, and fish are readily absorbed by dairyproducts, eggs, meats, and nuts. Some prod-ucts, such as apples, are capable of both giv-ing off and receiving odors. Loading combi-nations to avoid are apples or pears withcelery, cabbage, carrots, potatoes, or onions;celery with onions or carrots; and citrus fruitswith any of the strongly scented vegetables.Apples and pears may acquire an earthy tasteand odor if shipped with potatoes.

Use the “Load Compatibility Groups” sec-tion in appendix II for determining the load-ing compatibility of various products.

Whether Palletized or Unitized

Depending on the commodity and area ofproduction, anywhere from 75 to 90 percentof the fresh fruit and vegetable shipmentsare now unitized on pallets or slipsheets.Unitized shipments offer the advantages ofreduced labor and less manual handling ofthe product, but have unique loadingrequirements for protecting food productsduring transit. (See also the section “Load-ing Methods.”)

Length of Transit Period

The length of time a product will be in tran-sit will affect loading decisions. For exam-ple, a denser loading pattern can be used inan overnight shipment compared to one thattakes several days in summer heat. In over-seas shipments where transit periods may be2 weeks or longer, it is imperative that all ofthe recommended transit requirements forthe individual commodity be met to assuremaximum shelf life.

20

Basic Terminology

Figure 9 is a dimensional view of a load in atruck trailer showing arrangement of con-tainers in rows, stacks, and layers. A row isa line of containers extending the length ofthe trailer, one container in width, and ashigh as the load itself. A layer is a course orstratum of containers, one container high,usually extending the length and width ofthe trailer. A stack is a line of containersextending from one side wall to the otherand from the top to the bottom of the load,parallel to the front and rear end of the vehi-cle, and one container in length.

Loading Vehicles with Top-air Delivery

Hand-stacked LoadsWhen hand-stacking respiring product intrailers with top-air delivery, use an airflowpattern. The goal in airflow patterns is tobuild air channels through and around theload to maximize the circulation of refriger-ated air for interception of heat penetratingthe trailer body and removal of heat from theproduct. Figures 10a, b, and c illustrate atypical airflow pattern with horizontal airchannels constructed between rows in alter-nate layers. This pattern may be modified ina number of ways to accommodate varying

IV. Loading and Load Patterns

Figure 9. Dimensional view of aload in a truck semi-trailer showing arrange-ments of containers inrows, stacks, and layers.

LAYER

LAYER4TH3RD2ND1ST

STAC

21

vehicle and container sizes (figure 11).

To maximize cooling of hand-stacked loadsin vehicles with top-air delivery:

• use an airflow loading pattern for respiringproducts (figure 10);

• build a header or starter stack against the

front bulkhead with vertical channels tofacilitate air flow from the horizontal loadchannels back to the refrigeration unit (figures 10a and b); (After the starterstack, all other stacks in the load must beexactly the same, or the horizontal chan-nels will be blocked.)

• load top boxes in a solid layer to prevent

Figure 10. A typical airflow loadingpattern for commoditiespacked in fiberboardboxes: (a) longitudinalview, (b) header stack,and (c) rear view of allother stacks.

(A) LONGITUDINAL VIEW

DISCHARGE AIREVAPORATOR

BULKHEAD WALL

RETURN AIR

FAN

CONDENSER

HEADER STACK

(C) REAR VIEW(B) HEADER STACK

Blower Duct

22

air from short-circuiting back to the refrig-eration unit;

• do not load so high that the air chutes arecompressed and air circulation is blocked;

• allow at least 4 inches (10 cm) of openspace between the end of the load and therear doors for air return; and

• provide adequate space for air return underthe load (figure 5). (If the floor channelsare less than 2 inches (5 cm) deep, theproduct should be loaded on floor racks orpallets with their stringers running length-wise for greater airflow under the load.)

Unit LoadsTo enhance cooling of unit loads on palletsor slipsheets in trailers with top-air delivery:

• secure containers to each pallet withappropriate strapping, tape, plastic film, ornetting;

• load the pallets in rows and off the walls(figures 12a and b);

• load the pallets with their stringers runningthe length of the trailer; and

• secure the load with spacers and bracing toprevent the product containers from top-pling and blocking air spaces between thewalls and rows of pallets.

Loading Vehicles with Bottom-air Delivery

Design load patterns in bottom-air deliveryvehicles to maintain air pressure under theload. Respiring produce should be packed inboxes with top and bottom vent holes.

For hand-stacked loads in vehicles with bot-tom-air delivery the following apply:

• Load cartons tightly together from front to rear and sidewall to sidewall of the vehicle.

• Stack cartons with top and bottom ventholes directly on top of each other with thevent holes aligned.

• Leave at least 4 inches (10 cm) betweenthe top of the load and the ceiling for air toreturn to the refrigeration unit.

• Block any space left open on the top of theT-rails at the rear of the vehicle so that airwill be forced upward through the load andnot short circuit around the end of the loadat the doors (figure 3).

For unit loads on pallets or slipsheets invehicles with bottom-air delivery, observethe following:

• Load the unit loads together as tightly aspossible.

• Cover floor space not covered with theunit loads with fiberboard or other appro-priate material to force the air up throughthe unit loads.

• Ensure that there are holes or slots in ply-wood pallet floors or slipsheets to allowrefrigerated air into the unit load.

• For nonfrozen loads, block the ends of thepallets at the rear of the load to assure thatair pressure is maintained under the load.

Figure 11.Rear view of an airflowloading pattern modifiedfor wirebound crates.

23

Figure 12. End and overhead views ofbasic pallet or unit load pat-terns in a semi-trailer: (a) air-flow, (b) center-loaded, (c) wall-loaded, (d) off-set againstwalls, and (e) pinwheel. (Note:Pallets used in pinwheel pat-terns must be 4-way, or air flowunder the load will be blocked.)

SPACER BLOCKS

(B) PALLETSCENTER-LOADED

SPACER BLOCKS

SPACER BLOCKS

(A) PALLETSAIRFLOW LOADED

(C) PALLETSWALL LOADED

(D) PALLETSOFFSET LOADED

(E) PALLETSPINWHEEL LOADED

BULKHEAD WALL

BULKHEAD WALL

BULKHEAD WALL

BULKHEAD WALL

BULKHEAD WALL

24

The load patterns in figures 12c and d arerecommended for exporting palletizedgrapes and tree fruit in van containers withbottom-air delivery systems.

Unit or Pallet Loads

In top-air delivery trailers, unit or palletloads are usually loaded in one of five basicpatterns (figure 12). The dimensions of thepallet base and the interior dimensions ofthe vehicle will have considerable influenceon the pattern used. The amount of bulge,overhang, whether top-iced, and ventilationrequirements are other determining factorsfor unit load patterns.

Design unit load patterns to reduce thecontact of the product with the walls andfloor of the vehicle, especially if the vehi-cle is not equipped with inverted ribbedwalls and deep channel or high airflowfloors. Figure 13 shows the effect of unitand pallet load patterns on the amount ofproduct exposed to contact with wall andfloor surfaces. Reducing the amount ofsurface contact will improve productarrival temperatures and reduce the chanceof product freezing or warming in extremeweather conditions.

Stack shipping containers for unit loadssquarely on the pallets and stabilize to pre-vent toppling. Strapping, both vertical andhorizontal, is a popular method for stabiliz-ing unit loads. This method can be enhancedby the use of corner boards (figure 14).Also, palletizing glue (which has strength inshear and not in tension) may be usedbetween layers of containers. Net wraps andplastic stretch or shrink film wraps also maybe used.

CAUTION: Ensure that film wraps are notused on products that are improperly pre-cooled and/or have a high respiration rate asthe film may block ventilation and allowheat buildup. The top two or three layers ofa unit load sometimes are cross-stackedand/or taped horizontally for stabilization.

Brace unit loads to prevent them from shift-ing against the rear doors and blocking air-flow around the end of the load. Figure 15

illustrates an easily constructed woodenbrace. Load lock bars also help preventshifting.

Some loads are partly unitized and partlyhand-stacked. In this case, put the hand-stacked portion on pallets to make it consis-tent with the rest of the load and allow bet-ter air circulation.

Vented Loads

In some cases, ambient air is vented throughtrailers to cool loads of fresh produce. Also,fresh air may be vented into the vehicle toprevent oxygen starvation or to displacemetabolic gases such as ethylene or carbondioxide. For proper ventilated cooling ofhand-stacked loads, use an airflow loadingpattern (figure 10). In a vented load, the airenters a vent door at the top front of thetrailer, travels down under the bulkhead,through the horizontal air channels, andexits at a vent at the bottom of the rear door.

CAUTION: Ensure that the ambient air isnear the product’s desired transit tempera-ture and not so cold or hot that it will injurethe product. The product may also be dam-aged if substantial amounts of heat or fumesfrom the tractor’s exhaust stack are able toenter through the front vent. When vent-cooling loads, open all available vent doorsat the rear of the trailer.

For vented cooling of unitized loads, theload patterns shown in figures 12a, b, and care preferred.

Top-iced Loads

Use the pattern shown in figure 16 for hand-stacked loads that will be top-iced. Stackboxes or wirebound crates directly on top ofeach other in lengthwise rows. Divide thecrosswise slack space evenly between therows and walls for top-ice to fill. Placewood strips horizontally to stabilize the loadand maintain space between the rows.

The recommended procedure is to apply thecrushed ice on top of the load in threelengthwise windrows. The thermostat should

25

be set at 35oF (2oC) to allow the ice to meltsteadily during the trip. A colder setting maycrust or freeze the ice and block air circula-tion, thus allowing heat buildup in the interi-or of the load.

CAUTION: Ensure that the crushed ice isnot cold enough to freeze the produce oncontact. Ice may come out of cold storage ascold as 25oF (–4oC).

Figure 13. Effect of different unitload patterns on the per-centage of cartons con-tacting the floor andwalls in a typical load ofa perishable product.

(a) WALL LOADED = 20%

PRODUCT ON SLIPSHEETS

(b) CENTER-LOADED = 5%

PRODUCT ON PALLETS

(c) WALL LOADED = 15% (d) CENTER-LOADED = 0%

( ) For both top- and bottom-air deliveryvehicles, avoid loading tight against flatwalls; use an offset-by-layers pattern forhand-stacked loads or center-load unitloads (figures 7, 10, and 12).

( ) Allow at least 4 inches (10 cm) of spacebetween end of load and rear doors forreturn air.

( ) Use pallets on floor if floor channels orducts are less than 2 1/4 inches (6 cm)deep.

( ) Secure hand-stacked loads at rear withwood gates, load bars, or other devices.

( ) Secure unit loads with one or more of thefollowing: air bags, bracing, shrink filmor netting, or strapping.

For palletized loads, the load patterns shownin figures 12a and b are preferred.

Loading Checklist

Use the following checklist when loadingtrailers with top-air delivery:

( ) Precool vehicle to desired thermostat setting.

( ) Shut off the refrigeration unit when load-ing at an open dock.

( ) Record product temperatures during loading.

( ) For hand-stacked loads, use an airflowloading pattern with a header stack andlengthwise air channels (figure 10).

26

Figure 14.Example of strappingand corner boards on aunit load.

HorizontalStrap

Vertical Straps

Corner Boards

27

Figure 16. Rear view of a stackingpattern with wood stabi-lizing strips for top-icedloads in wireboundcrates (shown) or waxedfiberboard boxes.

HORIZONTAL WOODSTABILIZINGSTRIPS

Figure 15. Example of a method forbracing a load at the reardoors.

Use wide board to fillspace between load

and door

Nominal 2x4(approx. Nominal 1x4

(approx.

• Highest freezing point:30.0oF (–1.1oC)

After harvest, most apples are held in bulkbins in cold storage until they are sold. Asorders are received, apples are packed incorrugated fiberboard boxes. After packing,the apples are palletized for transport to theloading dock. At the loading dock, they mayoccasionally be removed from the palletsand hand-stacked in the trucks.

Apples ripen steadily at temperatures above40oF (4oC): Therefore, refrigerate themimmediately after harvest. Hold and trans-port most varieties at the 30o to 32oF (–1o to0oC) temperature range. Some varieties,such as McIntosh, are subject to chillinginjury at long exposure to temperaturesbelow 38oF (3oC).

Transport apples taken from cold storage atthe same temperature at which they werestored. Since most apples are shipped attemperatures near their freezing point, theyare quite susceptible to freezing injury.Thermostatically controlled heating shouldbe used to prevent both freezing and over-heating in extremely cold weather.

Mature apples coming from cold storagebruise more easily than those recently har-vested and require more careful handling.Apples absorb odors quite readily. Theyshould not be shipped in mixed loads ofcommodities like onions or cabbage, nor intrucks harboring strong odors. Apples alsoproduce ethylene, and they should not beshipped with products sensitive to this gas.

Quality and shelf life at destination willdepend greatly on providing the recom-mended transport conditions. For loads withmore than one commodity, consult “LoadCompatibility Groups” in appendix II.

Make decisions on thermostat settings on aload-by-load basis, taking into account theoperating characteristics of individual trail-ers, the loading temperature of the product,and the desired transit temperature for theproduct loaded.

CAUTION: Be careful when determiningthe thermostat setting for fresh or chilledproducts transported at temperatures neartheir freezing point. Considerable freezingor chilling damage could occur, especiallyon the top layer of the load. This is becauseair exiting the refrigeration unit may be sev-eral degrees below the thermostat setting toattain a cooling differential with the air atthe return. For example, if the desired trans-port temperature of a product is 32oF (0oC)and the freezing point is 31.8oF (–0.1oC),then the thermostat setting would probablyneed to be in the 34o to 36oF (1.1o to 2.2oC)range to prevent product freezing.

Apples

Recommended transport conditions:

• Desired transit temperature:Most varieties: 30o to 32oF (–1o to 0oC)Cortland, McIntosh, and Yellow New-town: 38o to 40oF (3o to 4oC)

• Desired relative humidity:90 to 95 percent

28

V. Individual Commodity RequirementsFresh Fruits and Vegetables

29

Recommended loading methods:

• Fiberboard boxes—Nearly all apples areshipped in fiberboard boxes. The apples maybe packed in the boxes loose, in polyethylenebags, or in molded trays. Stack the boxeslengthwise or crosswise in the vehicle.

• Fruit from cold storage—Stack the boxestightly together. However, in extreme hot orcold weather, use an offset by layers patternfor reduced contact with the walls and floor(figure 7).

• Palletized fruit—Center-load (figure 12b)in extreme hot or cold weather to reducecontact with walls. Do not overfill bin loadsto prevent apples in the bottom bins frombeing bruised.

Apricots


• Desired transit temperature:32oF (0oC)



Apricots should be firm when shipped, sothey will have a 1- to 2-week shelf life. Pre-cool to the desired transit temperature. Someshippers use forced-air coolers, while othersroom cool their fruit. Apricots may beshipped with other tree fruit commoditiesfrom the same or nearby packing houses. Ifapricots are shipped in mixed loads that aretop-iced, ice should not contact the apricots.


• Fiberboard boxes—Boxes of apricots gen-erally are unitized on wood pallets. Securethe boxes with straps or plastic netting. Ifthe apricots are not precooled to the transittemperature, place fiberboard strips betweenthe stacks of boxes on the pallet so that coldair may circulate freely around them. If theweather is very hot and the trailer has flatsidewalls, center-load the pallets to preventthe transfer of heat from the walls to thefruit (figure 12b).

Artichokes





• Top- or package-ice OK

Precool artichokes as soon as possible afterharvest to reduce wilting, weight loss, discol-oration, and decay. Use top-ice to preventwilting or loss of turgidity and to keep thebuds near the desired transit temperature foradded shelf life. The marketability of arti-chokes is reduced by bruising or freezing.Severe freezing turns the buds black andslight freezing causes skin breaks and blisters.


• Fiberboard boxes—Most artichokes arepacked in waxed fiberboard boxes which arestacked on their bottoms either lengthwiseor crosswise on pallets. See figure 12 forunit load patterns.

Asparagus


• Desired transit temperature:32o to 35oF (0o to 2oC)



Asparagus is highly perishable. Speed andcare are required during handling and transitto prevent excessive loss of quality. As soonas asparagus is cut, its natural sugars, flavor,and vitamin C begin to diminish rapidly,particularly at temperatures above 36oF(2oC). Hydrocooling is the most desirablemethod of precooling.

Asparagus is usually packed in bunches andset upright in the shipping container to pre-vent bruising and curling of the tender tops.

30

To prevent moisture loss and preserve crisp-ness during transit, place pressed paperboardor other water-retaining material in the bot-tom of the pyramid-shaped wooden box orwaxed corrugated fiberboard box.

A modified atmosphere of about 7 percentCO2 is beneficial in preventing decay andtoughening of fresh asparagus. This is espe-cially true if temperature control cannot bebrought below 41oF (5oC).


• Nailed wooden boxes (pyramid-shaped)—Load boxes lengthwise on their bottoms andstack in register. The slope of the pyramidallows open space for continuous lengthwiseair channels on each layer in hand-stackedloads. For palletized loads, use a center-loadpattern as shown in figure 12b.

• Fiberboard boxes (waxed corrugated)—Load boxes lengthwise or crosswise on theirbottoms and palletize. Use a center-load pat-tern as shown in figure 12b.

Avocados


• Desired transit temperature:Cold-tolerant varieties:Such as Lula and Booth No. 8 40oF (4oC)Cold-intolerant varieties: All West Indian varieties, which includeFuchs, Pollack, and Walden55oF (13oC)



A few varieties, such as Fuerte, are bestshipped at 45oF (7oC). Gradual ripening ofavocados may occur at temperatures as lowas 45oF (7oC). The rate of ripening and soft-ening of the fruit increases as the tempera-ture rises. Therefore, it is important to pre-cool avocados before loading. Belowrecommended temperatures, avocados aresusceptible to chilling injury. Commonsymptoms of chilling injury are a grayish-

brown discoloration of the flesh, scaldingand/or pitting of the skin, and failure of thefruit to ripen satisfactorily after storage ortransit. At temperatures higher than recom-mended, anthracnose or black spot canbecome serious disorders.


• Fiberboard boxes—Both California andFlorida shippers use fiberboard boxes forpacking avocados. Shippers in both areaspredominantly use a one- or two-layer box,and generally palletize their avocados. Forhand-stacked loads, use an airflow pattern(figure 10). For transport in extremely coldweather, center-load pallets in vehicles with-out ribbed walls to prevent chilling injury(figure 12b).

Bananas





Bananas are imported into the United Statesyear-round from various Central and SouthAmerican countries. The Cavendish varietyis most commonly imported. Bananas areshipped green and ripened at destination.They are very temperature sensitive; lowerthan desired temperatures will cause chillinginjury, and higher than desired temperaturesmay cause rapid and improper ripening.Proper air circulation is required to maintainuniform temperatures throughout the load,since fluctuating temperatures are detrimen-tal. Provide a fresh air vent to prevent ethyl-ene gas buildup inside the trailer which willcause premature ripening. Also, do not shipbananas with other produce that is not tem-perature compatible or that produces highamounts of ethylene.


• Corrugated fiberboard boxes—Nearly allbananas are packed in heavy duty, plastic

31

film-lined fiberboard boxes at the country oforigin. The gross weight of the boxes is 40pounds (18 kg). They then are transported tothe United States in refrigerated containersor on break-bulk ships under carefully con-trolled temperature and humidity conditions.

Since bananas are easily bruised, do notthrow or drop the boxes during handling.Place the boxes on their bottoms, and do notinvert or stack them on their sides. If not pal-letized, load the boxes crosswise or length-wise and stack tightly together to get a denseload. In extremely cold weather, use floorracks or pallets in vehicles without deep T-rail floors to prevent freezing or chillinginjury. If the walls are not grooved, center-load pallets off the walls (figure 12b). Hand-stack boxes in an offset by layers pattern(figure 7a) to reduce contact with the walls.

Beans (green, snap, or pole)



• Desired relative humidity:95 percent


Green or snap beans are highly susceptibleto chilling injury which predisposes them torusseting and other discoloration. Tempera-tures in the 40o to 45oF (4o to 7oC) rangeare considered best for shipping beans, eventhough some varieties may incur some chill-ing injury after several days at 45oF (7oC).At temperatures above 50oF (10oC), beansmay decay rapidly. Precool beans beforeshipment but do not pack wet, as this willincrease the chance of russeting and decay.

Use of a controlled atmosphere in the 2 to 3percent oxygen and 5 to 10 percent carbondioxide ranges will help retard yellowing ofgreen beans. Green beans also are sensitiveto ethylene and should not be shipped withethylene producers.


Stack and load containers of green beans to

allow maximum air circulation for respira-tion heat removal.

• Wirebound crates—Load wirebound crateslengthwise on their bottoms in an airflowpattern (figure 11).

• Fiberboard boxes—Load fiberboard boxesin an airflow pattern (figure 10). Increasing-ly, fiberboard boxes and wirebound crates ofbeans are palletized. Pallet patterns shownin figures 12a, b, or c allow good air circula-tion if pallets are properly secured.

Beans (lima, in pods)




• Highest freezing point:31oF (–0.6oC)

Fresh lima beans in pods will keep from 5 to7 days if held and shipped within the desiredtemperature range. Higher holding tempera-tures will greatly reduce the market life ofthe beans.

Precool lima beans immediately after har-vest, preferably by hydrocooling. The podsare susceptible to chilling injury below therecommended transit temperature. Chillinginjury results in rusty-brown specks on thepods.


• Wirebound crates and waxed fiberboardboxes—Hand-stack boxes and crates in anairflow pattern (figures 10 and 11).

• Palletized loads—See figure 12 for illus-trations of unit load patterns.

Beets




32

• Highest freezing pointTops, 31.3oF (–0.4oC)Roots, 30.3oF (–0.9oC)

• Top-ice OK

Beets are shipped bunched with tops orloosely packed without tops. Those shippedin bunches are highly perishable because ofthe heat generated by the tops. They shouldbe both package- and top-iced for maximumrefrigeration and moisture retention. Theleaves of bunched beets are especially sus-ceptible to bacterial soft rot. Transit andmarketing losses caused by this disease canbe controlled by rapid precooling and main-tenance of temperature at 32oF (0oC). Late-crop beets are topped and may beshipped immediately or stored for later ship-ment. They are fairly decay resistant as longas their skins are not broken and cool tem-peratures are maintained. However, it isdesirable to top-ice long distance shipmentsin hot weather.


• Bunched in wirebound crates—Load crateslengthwise on their sides. If top-iced, stackdirectly on top of each other and leave 1inch (2.5 cm) or more between the length-wise rows for ice to fill (see figure 12). Ifnot top-iced, precool the beets, and use anairflow loading pattern (figure 11).

• Topped in wirebound crates—Hand-stackcrates of topped beets in an airflow pattern(figure 11). If beets are top-iced, see figure 16.

• Palletized—See “Unit and Pallet Loads” insection IV, and figure 12b.

Beet TopsBeet tops have essentially the same transitand handling requirements as fresh spinach.See “Spinach” in this section.

Blackberries


• Desired transit temperature:31o to 32oF (–0.6o to 0oC)



Fresh blackberries are highly perishable.They usually are not shipped over long dis-tances by truck since their shelf life is limit-ed to a few days. Maintaining their tempera-ture near the desired 32oF (0oC) is veryimportant. An atmosphere of 10 to 20 per-cent carbon dioxide (CO2) will help to retarddecay.


• Fiberboard trays—Corrugated fiberboardtrays usually interlock with the trays above.Hand-stack trays lengthwise on their bot-toms with space between the rows for air-flow. Place wood strips crosswise aboutevery fourth layer for stabilization.

Most shippers palletize the trays of berriesto minimize handling. Strap the trays secure-ly to the pallets. Center-load the pallets,two-wide, and brace away from the walls, sothat air can circulate around the load andeliminate the conduction of heat from thetrailer walls to the fruit. Major shippersenclose the pallet loads of berries with air-tight plastic bags and inject a modifiedatmosphere for increased protection againstdecay and extended shelf life (figures 12band 17).

Blueberries


• Desired transit temperature:31o to 32oF



Blueberries are very temperature sensitive.Temperatures much above the desired hold-ing temperature cause over-ripening, shrivel-ing, and loss of shelf life. Avoid moisture onberries caused by condensation or othersources, while in transit. A minimum of han-dling, close temperature control, and expe-dited shipment and marketing are essentialfor successful sales since blueberries have a

33

shelf life of only about 2 weeks under opti-mum conditions. Modifying the atmospherewith CO2 in conjunction with refrigeration iseffective in retarding decay in blueberriesbut may result in off-flavors.

Recommended Loading Methods:

• Fiberboard Trays—Blueberries are gener-ally packed in film-covered pint- (0.47-l)sized containers. A plastic film cap is tightlysecured on each container by a rubber band.Berries also may be packed in clear clamshell container. Twelve containers of berriesare packed in a fiberboard tray. The trays arenearly always palletized for shipment. Cen-ter-load the pallets, and brace away from thewall, eliminating the conduction of heat

from the trailer walls to the fruit (figure12b).

Broccoli





• Top- and/or package-ice desirable

The respiration rate of broccoli is among thehighest for vegetables. Therefore, refrigera-

Figure 17. A palletized load ofstrawberries, center-loaded. (Note: Each pal-let load is enclosed in anairtight plastic baginjected with a modifiedatmosphere.)

34

tion at or just above the desired transit tem-perature is required at all times. Exposingbroccoli buds to temperatures above 50oF(10oC) for only a short while will result inyellowing and reduced marketability. Pro-vide fresh air exchange in the trailer to pre-vent anaerobic respiration and undesirableodors. Broccoli is sensitive to ethylene, sodo not ship it with fruit, such as apples orpears, that produce substantial amounts ofethylene, because this gas will cause yellow-ing of the buds.


Broccoli is usually packed in waxed fiber-board boxes with crushed ice. After theboxes are loaded, top-ice the load.

• Fiberboard boxes—Load boxes length-wise on their bottoms. Align rows withspace between them for top-ice (figure 16).When the boxes have top and bottom venti-lation slots, stack them in register, so thatmelt-water from the ice can run downthrough the product. Load hand-stackedboxes that are not top-iced in an airflowpattern (figure 10). Load top-iced, pal-letized loads of broccoli in any of the unitload patterns shown in figure 12.

Note: If shrink film is used to secure thepallet loads, make sure the film does notcover the top, so melt-water can filter downthrough the broccoli.

Brussels Sprouts





• Top- and/or package-ice OK

Keep brussels sprouts near the desired 32oFto attain the maximum shelf life of 3 to 5weeks. At 41oF the deterioration rate ofbrussels sprouts doubles. Do not ship themwith ethylene-producing fruit, because brus-sels sprouts will yellow. Use perforated plas-

tic package liners to help prevent moistureloss from transpiration. A controlled or mod-ified atmosphere of 2.5 to 5 percent oxygenand 5 to 7.5 percent carbon dioxide atmos-phere helps maintain the quality of brusselssprouts at 41oF or 50oF, but not at 32oF.


Brussels sprouts are shipped mostly inwaxed fiberboard cartons with package- ortop-ice. Use the same loading procedures asthose for broccoli. See preceding entry,“Broccoli.”

Cabbage





Cabbage is less perishable than many otherleafy vegetables. Wilting from moisture lossis the main cause of damage during handlingand transporting. Stored cabbage is less like-ly to wilt during transit than new cabbage.Except for a few new crop shippers, mostshippers do not top-ice cabbage. Stored cab-bage should not be top-iced. Several kindsof decay, such as bacterial soft rot andwatery soft rot, may damage cabbage duringtransit if the desired temperature is notmaintained.


• Wirebound boxes—Load boxes lengthwiseon their bottoms. Most shippers offset thecrates by layers to take up slack space andstabilize the load (figure 7a). Use an airflowpattern (figures 10 and 11) for crates of newcabbage that are not top-iced. If top-iced,load the crates lengthwise in rows with theslack space evenly divided between the rows(figure 16).

• Fiberboard boxes—Load boxes lengthwiseon their bottoms in an airflow pattern (figure10). For palletized loads, see figure 12.

35

Cantaloupes





• Top-ice OK

After harvest, cantaloupes are forced-air orhydro-cooled to prevent them from becom-ing soft during long-distance transport.Although they are chill sensitive, canta-loupes are not harmed by extended contactwith ice. Up to 10 lbs (4.5 kg) of crushedice may be placed in boxes of cantaloupesafter they are packed. Or, the loads may betop-iced if the cantaloupes are packed inmoisture resistant boxes.

Cantaloupes picked at the hard-ripe stage ofmaturity are subject to chilling if held attemperatures below 36oF (2.2oC) for longerthan 1 week. For normal truck shipments ofless than 1 week, temperatures between 32o

and 34oF (0o to 1oC) will not be harmful. Cantaloupes produce ethylene, so do notship in mixed loads with ethylene-sensitiveproducts such as green leafy vegetables.


• Fiberboard boxes—Stack boxes holding 9to 23 cantaloupes each, six or seven layershigh on pallets. Load the pallets, two across,the width of the truck. If top- or package-iceis used, the boxes must be moisture resistant,and floor drains should be open so that melt-water will not accumulate on the trailer floor.See figure 12 for pallet loading patterns.

Carrots




• Highest freezing point:

29.5oF (–1.4oC)

• Top-ice OK

Hydrocool carrots after harvest to ensure anadequate shelf life. Top-ice topped carrotsfor moisture retention. Carrots are shippedto market loose in bulk bags or fiberboardboxes or packed in consumer size plasticbags within larger mesh bags or in fiber-board boxes. Do not ship carrots with ethyl-ene-producing commodities, because thiswill cause the carrots to have a bitter flavor.


• Open mesh or plastic film bags—Carrotsin bags usually are stacked so that, whenloaded, the carrots are in a vertical position.Load hand-stacked bags in rows with spacesbetween for top-ice. Wrap palletized loadswith net, or strap for stability. See figure 12for pallet load patterns.

• Corrugated fiberboard boxes (waxed)—Carrots usually are packed horizontally infiberboard boxes. Hand-stack boxes length-wise on their bottoms in an airflow pattern(figure 10). Column-stack boxes loaded onpallets or slipsheets in the lower layers toretain their strength. Cross-stack the boxesin the upper layers for stability. See figure12 for pallet load patterns.

Cauliflower





• Top-ice OK

Precool cauliflower by vacuum or hydromethods before loading. To control decay,keep cauliflower below 40oF (4oC). If cauli-flower is packed in moisture resistant boxes,it can be top-iced. Take care not to bruise thebuds or heads during loading and handling.

36


• Corrugated fiberboard boxes—Hand-stackboxes in an airflow pattern (figure 10). MostWest Coast loads are packed in single-layerboxes and palletized. Do not load the palletsso high that the top layer of boxes compressthe air-delivery chute and restrict airflow.This may result in poor air circulation andwarm or freezing spots in the load. See fig-ure 12 for pallet loading patterns.

• Wirebound crates—Hand-stack crates inan airflow pattern (figures 10 and 11).

Celery





• Top-ice OK

Soon after harvest, precool celery to below40oF (4oC) by either hydrocooling or vacu-um cooling to limit decay. After harvest cel-ery continues to grow, so pack it upright inthe container. Sometimes celery is sleevedor bagged at the shipping point. The sleeveshelp retain moisture and prevent wiltingwhich is a main cause of deterioration.Some shippers who use wirebound cratestop-ice their celery, but this practice is notrequired if the celery is sleeved.


• Wirebound crates—Load crates lengthwise ontheir sides to protect the stalks from damage andallow the celery to grow straight. Hand-stack top-iced celery in rows with spaces between for top-ice to fill (figure 16). If not top-iced stack in an air-flow pattern (figures 10 and 11).

• Fiberboard boxes—Most celery that ispacked in fiberboard boxes is vacuum-cooledand, therefore, not top-iced. Load the boxeslengthwise on their sides. Load boxes packedwith celery hearts lengthwise on their bot-toms. In either case, load hand-stacked boxesin an airflow pattern (figure 10).

Considerable amounts of crated and boxedcelery are palletized. Figure 18 shows amixed palletized load of celery and greenonions loaded in the recommended airflowpattern. See “Unit or Pallet Loads” sectionand figure 12a.

Cherries


• Desired transit temperature:Sweet cherries: 30o to 32oF (–1o to 0oC)Sour cherries: 32oF (0oC)


• Highest freezing point:Sweet cherries: 28.8oF (–1.8oC)Sour cherries: 29.0oF (–1.7oC)

Cherries are highly perishable, so refrigerateto the desired transit temperature beforeloading. In conjunction with refrigeration,consider using a modified atmosphere withup to 20 percent CO2 to maintain the qualityof cherries during transit.

Washington and Oregon cherry shippersplace a polyethylene bag liner in the box.Respiration of the fruit in the bag will buildup a sufficient concentration of CO2 toretard decay and help maintain a freshappearance. However, the liners should beslit at destination to eliminate gas buildupand off flavors. California shippers do notuse box liners. Increasingly pallet lots ofcherries enclosed in plastic bags and treatedwith a modified atmosphere are beingshipped.


• Wooden lugs—Most cherries are volume-filled. Unitize on pallets, and secure withstrapping or plastic netting. See figure 12 forpallet load patterns.

• Corrugated fiberboard boxes—Increasingamounts of cherries are shipped in fiber-board boxes. Like the wooden lugs, theymay be secured to the pallets with verticaland horizontal bands or plastic netting. See“Unit or Pallet Loads” section and figure 12for information on pallet loading.

37

Corn (sweet)





• Top-icing very desirable

The sugar in freshly harvested sweet cornwill turn to starch rapidly unless field heat isremoved quickly. At room temperature, corncan lose 50 percent of its sugar in 24 hours.However, if the temperature is lowered to32oF (0oC) soon after harvest, only 24 per-cent is lost in 4 days. Many newer varietiesof corn retain their sugar content for longer

periods than older varieties. In most growingareas, corn is hydrocooled, and in someareas, it is vacuum-cooled.

Corn has a high respiration rate and requiresmaximum refrigeration during transit. Top-icing retains moisture and maintains a lowtemperature in corn during transit. If thecorn is vacuum-precooled, top-icing is espe-cially desirable to replace moisture lost fromthe husks. When the load is top-iced, set thethermostat at 36oF (2oC) so that the ice willmelt. If the thermostat is set at or belowfreezing, ice may crust on top of the loadand block air circulation and keep melt-water from cooling corn in the bottom of theload.

Prepackaging several ears of corn in film-covered trays for retail at the grower level isa rapidly growing practice. The trays are

Figure 18. A mixed palletized loadof celery and greenonions loaded in a unitload airflow pattern.

38

subsequently packed in fiberboard boxes forshipment. Do not top-ice these boxes. Ifcorn is not top-iced, ship it at 32oF.


• Wirebound crates—The majority of Flori-da sweet corn is shipped in wirebound cratesloaded lengthwise on their sides. Alignrows, keeping adequate space between themto allow for top-ice (figure 16). Anotherloading pattern calls for loading the crateslengthwise on their sides with no spacebetween rows in the first two or three layers.The upper layers have one less row and areoffset over the bottom layers with severalinches of space between rows. Place woodenstrips horizontally across the top of eachlayer to prevent the crates from toppling andblocking the space between rows. This load-ing method allows a large volume of top-iceto get between the rows in the upper layersand melt water to run directly through thebottom layers.

• Fiberboard boxes—Load boxes lengthwiseon their bottoms. Moisture-resistant fiber-board boxes have openings only in the topand bottom for top-ice melt-water to rundown through the layers. Stack these boxesin register or squarely over each other so themelt-water can run down through all of thelayers of the stack.

Load boxes or crates without top-ice in anairflow pattern (figures 10 and 11). Loadpallets as shown in figure 12a or 12b toassure maximum top-ice infiltration in top-iced loads or air circulation in loads withouttop-ice.

Cranberries

Recommended transit conditions:




Cranberries are primarily grown in Wiscon-sin, Massachusetts, New Jersey, Oregon, andWashington, and are harvested and availablefor fresh distribution from September

through December. Cranberries can be heldat temperatures of 36o to 40oF (2o to 4oC)up to 4 months. Cranberries will toleratetemperatures as low as 32oF (0oC) for up to2 weeks. However, exposure for longer peri-ods could cause chilling damage resulting indiscoloration and rubbery texture. Handlecranberries with care since they are suscepti-ble to bruising. Precool cranberries to near40oF (4oC) before loading, because the insu-lation effect of the packaging makes it diffi-cult to lower temperature during transit.


• Fiberboard master cartons—Cranberriesfor the fresh market are packed in 1-lb(0.45-kg) film bags or window boxes andshipped in master fiberboard containers thatwill hold 24 1-lb packages. For hand-stacked loads, stack the master fiberboardcartons lengthwise on their bottoms in anairflow pattern (figure 10).

For palletized loads, center-load as shown infigure 12b.

Cucumbers





Generally, cucumbers do not require pre-cooling before transit. However, store themso that excess field heat will be removedwithin 24 hours after harvest, or yellowingwill occur. Yellowing also may occur ifcucumbers are shipped in mixed loads withtomatoes or other ethylene-producing prod-ucts. Cucumbers are subject to chillinginjury if held or transported for longer than2 days at temperatures below 50oF (10oC).Decay is controlled by maintaining transittemperatures near desired levels. However,at higher temperatures bacterial diseases canbe a problem. Cucumbers are very suscepti-ble to shriveling, so keep humidity high dur-ing storage and transit. Also, cucumbersusually are waxed to prevent shriveling.

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• Fiberboard boxes—Most cucumbers arepacked in various sizes of fiberboard boxes.Load hand-stacked boxes lengthwise ontheir bottoms in an airflow pattern (figure10). Many shippers palletize their cucum-bers. See “Unit or Pallet Loads” section forpallet loading patterns.

Eggplants


• Desired transit temperatures:46o to 54oF (8o to 12oC)



Some eggplant fruit are subject to chillinginjury at 50oF (10oC) and below. Surfacescald or bronzing and pitting are symptomsof chilling injury. Chilled eggplants are sub-ject to Alternaria rot when removed fromstorage or transit. Chilling sensitivity variesby season of harvest, variety, and maturity.Overmature fruit harvested in the fall is lesssensitive to chilling than mature fruit har-vested in the summer. Mature eggplants har-vested midsummer are highly susceptible todecay at temperatures higher than 54oF(12oC) and chilling injury below 50oF(10oC). Eggplants shrivel very easily duringtransport and storage if the relative humidityis not kept at 90 percent.

Recommended loading patterns:

• Fiberboard boxes—Most eggplants arepacked in fiberboard boxes. Generally, loadhand-stacked boxes lengthwise on their bot-toms in an airflow pattern (figure 10). Manyshippers palletize their eggplant boxes eightper layer and five to six layers high. Loadpallets in an off-wall pattern (figure 12b).

Endive and Escarole





• Top-ice desirable

Endive and escarole are highly perishableleafy vegetables, similar to lettuce, whichrequire maximum refrigeration during tran-sit. They have a high rate of respiration, soprecool immediately after harvest by vacu-um or hydrocooling. Endive and escaroleoften are shipped in mixed loads with otherproducts, because most orders for theseproducts are for less than truckload lots.Top-ice or package-ice is desirable. If top-ice is applied to the load, set the thermostaton the refrigeration unit at 36oF (2oC) sothat the ice will melt slowly and run downthrough the load. If not top-iced, ship theproduct at 32oF (0oC).


• Fiberboard boxes (waxed)—Load theboxes lengthwise on their bottoms in an air-flow pattern, if not top-iced (figure 10). Iftop-iced, stack the boxes lengthwise or cross-wise in rows, directly on top of each other sothe melt-water can run down through the topand bottom vent holes (figure 16).

• Wirebound crates—Load crates lengthwiseon their bottoms in an airflow pattern (fig-ures 10 and 11). If top-iced, stack the crateswith slack space evenly divided between therows (figure 16).

Use unit load patterns (figure 12a or b) forpalletized loads of endive or escarole toassure space for air circulation or top-iceinfiltration.

Garlic (dry)





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Garlic is usually shipped from storage at32oF (0oC). In warm weather, take care toload the garlic promptly to reduce moisturecondensation on the product. Load in an air-flow pattern to remove any condensationthat does occur. Garlic cloves sprout rapidlyat temperatures above 40oF (4oC). Do notship garlic in mixed loads with odor absorb-ing commodities. Do not allow ice to comein contact with garlic.


• Fiberboard boxes—Load the boxes length-wise on their bottoms in an airflow pattern(figure 10). This pattern assures good venti-lation of the load to remove condensationand maintain desired transit temperature. Forpalletized shipments, use load patternsshown in figures 12a and b.

Grapefruit


• Desired transit temperatures:Arizona and California: 58o to 60oF

(14o to 16oC)Florida and Texas:

Before January 1—60oF (16oC)After January 1—50oF (10oC)



Grapefruit are very susceptible to chillinginjury, particularly early in the season. Chill-ing injury symptoms are pitting or physio-logical breakdown on the surface of the fruitwhich can be a means of entry for decayorganisms. Many types of decay organismscan attack grapefruit, particularly duringearly- and late-season shipments. Most ship-pers treat their grapefruit with approvedfungicides. Curing or preconditioning grape-fruit can counteract some of the adverseeffects of low temperature. To cure grape-fruit, hold at 60oF (16oC) for 1 week. Aftercuring, store or ship grapefruit at tempera-tures of 32o to 34oF (0o to 1oC) for up to 21days. Cured grapefruit may be stored orshipped with oranges at low temperatures.

Ventilate grapefruit loads during transit incool weather. However, during warm weath-er, refrigerate the loads.

CAUTION: 41oF (5oC) is the temperatureat which the danger of chilling injury tograpefruit is the greatest.


• Fiberboard boxes (loose filled)—Loadboxes lengthwise or crosswise on their bot-toms. Hand-stack loads in an airflow pattern(figure 10). Florida shippers mainly unitizetheir shipments on slipsheets. Many Califor-nia, Arizona, and Texas shippers unitizetheir shipments on pallets. See figure 12 forunit load patterns.

• Fiberboard boxes (bag master)—Loadboxes lengthwise or crosswise on bottoms.Hand-stack bag-master boxes in an airflowpattern (figure 10). Many bag-master boxesare unitized on slipsheets or pallets. Sincemost shippers do not precool their fruit, takeextreme care in transporting grapefruit inbag masters. The fruit is packed in polyeth-ylene film or mesh bags and packed inboxes which makes it more difficult to coolthe fruit in transit. Use the unit load patternsin figure 12a or b for bag-master packedgrapefruit that has not been precooled.

Grapes


• Desired transit temperatures:American types—Catawba, Concord,etc.: 32oF (0oC)European types (vinifera)—Thompsonseedless, Red Emperor, etc.: 31oF (–0.5oC)

• Desired relative humidity:American: 90 to 95 percentEuropean: 85 percent

• Highest freezing point:American types: 29.7oF (–1.3oC)European types (vinifera): 28.1oF (–2.2oC)

Precool grapes to their desired transit tem-perature before loading, and maintain thetemperature during transit. Normally, fumi-gate vinifera grapes with sulphur dioxide

41

gas (SO2) during storage and before ship-ment to control the spread of Botrytis (graymold) and Cladosporium decays. This fumi-gation will not kill infections that startedbefore harvest. For grapes that are packedfor export, use top cushion pads that containsodium bi-sulphite which will be slowlyreleased during transportation. Do not shipgrapes treated with SO2 with other productssince the gas odor may be absorbed.

Do not ship grapes with green onions, asthey may absorb the onion odor. Also, pre-vent grapes from coming in contact with ice.

WARNING: When using SO2 gas, take careto prevent injury to workers and equipment.SO2 fumes are toxic to humans and will cor-rode certain metals.


• Wood and kraft veneer, fiberboard, andpolystyrene foam boxes—Load hand-stackedboxes lengthwise on their bottoms in an air-flow pattern (figure 10). Most shipments ofgrapes are palletized. See figure 12 for palletload patterns. Use patterns shown in figures12c and d for export grapes loaded in vancontainers with bottom-air delivery systems.

Kale





• Top-ice OK

Kale, a leafy vegetable, has a high rate ofrespiration. It requires maximum refrigera-tion during handling and transit to maintainits quality. When kale is transported or keptat temperatures above 32oF (0oC), it maytemporarily appear to be in good condition.However, the higher temperatures willreduce its resistance to decay and yellowingof the leaves, and it will break down rapidlywhen displayed in stores.

To precool and to maintain crispness, packcrushed or slush-ice in each container ofkale. Spread a liberal amount of top-ice overloads which are not prepackaged.


• Wirebound crates—Align the crates withspace divided between the rows for top-iceto fill (figure 16). If not top-iced, load cratesin an airflow pattern (figures 10 and 11).

• Fiberboard boxes (waxed and unwaxed)—Load waxed boxes packed with loose kale instraight rows with space divided betweenthe rows for top-ice to fill (figure 16).

Prepackaged kale needs cold air circulatedto each box. Use an airflow pattern forhand-stacked loads (figure 10). For pal-letized loads going into a wide trailer, usethe pallet loading patterns (figure 12a or b)to allow air to circulate around the product.

Kiwi Fruit

Recommended transit conditions:




Cool kiwi fruit to 32oF (0oC) as soon afterharvest as possible, and maintain that tem-perature during transit. Take care to preventkiwi fruit from being exposed to ethylenegas. Use electric forklift trucks to handlekiwi fruit, since they do not produce ethyl-ene as propane-fueled trucks do. Do notship kiwi fruit in mixed loads with productsthat generate ethylene, such as apples andother tree fruit.


• Wood trays and fiberboard boxes—Loadtrays and boxes lengthwise on their bottoms.Most boxes of kiwi fruit are palletized forshipment. See figure 12 for pallet loadingpatterns.

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Lemons





Lemons are subject to chilling injury (pittingand physiological breakdown) if stored forlong periods at temperatures below 58oF(14oC). However, during domestic transitperiods of several days, rot and mold aremore likely to damage lemons than cold. Fortransit and storage periods up to 4 weeks,lemons may be held at any convenient tem-perature between 45o and 55oF (7o to 13oC)without incurring chilling injury. Lemonsusually are shipped from cold storage andare near the desired transit temperaturewhen loaded. They may be ventilated if out-side temperatures fall within the desiredtemperature range.


• Corrugated fiberboard boxes—Nearly alllemons consumed in the United States areproduced in Arizona and California. Thelemons are usually packed in fiberboardboxes and palletized for shipment. See fig-ure 12 for pallet loading patterns.

Lettuce (head)




Lettuce is one of the most perishable andeasily damaged of all commercial vegeta-bles. Individual lettuce heads usually arefield packed unwrapped or wrapped in plas-tic film, then packed in fiberboard boxes.Vacuum-cool field-packed lettuce, and placein cold rooms until ready for loading. Or

vacuum-cool the lettuce immediately beforeloading. Because it is difficult to cool let-tuce in transit, take several product temper-atures during loading to make sure that thelettuce is near the desired transport temper-ature. Lettuce is sensitive to ethylene gas,so do not load it with ethylene-producingcommodities. In extreme temperatures, loadlettuce up off the floor on pallets or floorracks and away from the side walls of thetrailer to prevent warming or freezing. Donot ice lettuce.


• Fiberboard boxes—Lettuce boxes usuallyare unitized and mechanically loaded.Many different types of load patterns areused, depending on the individual ship-per’s equipment. Since lettuce heads are oflow density and high cube, there is a ten-dency to load it tightly, without air chan-nels. Extremely tight loads, especially intrailers with flat walls, may overheat orfreeze in extreme temperatures. During hotweather, load the lettuce on disposablewooden floor racks to allow additional air-flow under the load. See figure 12 for pal-let load patterns. In hot weather, use pat-tern 12b. Load hand-stacked boxes in anairflow pattern (figure 10).

Lettuce (leaf)





All varieties of leaf lettuce (Bibb, Boston,butter, etc.) are very perishable and easilydamaged. Precool leaf lettuce immediatelyafter harvest by either vacuum or hydrocool-ing. Once lettuce is precooled, ship it asnear to 32oF (0oC) as possible and at highrelative humidity. At higher temperatures,the rate of respiration is high, and bruisedareas will disease rapidly. Bacterial soft rotis the most serious lettuce disease.

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• Fiberboard boxes (waxed)—Load hand-stacked boxes lengthwise on their bottomsin an airflow pattern (figure 10). There aremany kinds and sizes of fiberboard boxesused for shipping leaf lettuce. However,most shippers pack 12 or 24 bunches perbox. If palletized, see figure 12 for loadingpatterns. Use the pattern shown in figure12b for shipments in extreme temperatures.

• Wirebound crates—Load crates lengthwiseon their bottoms in an airflow pattern (fig-ures 10 and 11).

Limes





Limes are picked green and should remaingreen during marketing for best quality.After harvest, limes are sorted, packed andprecooled to around 50oF (10oC) in refriger-ated rooms. Limes are subject to attack byblue- and green-mold and stem-end rot.Limes picked when over-mature may devel-op stylar-end breakdown during transit.Green color is maintained better at lowertemperatures, but pitting (chilling injury)may occur when limes are held at tempera-tures below 46oF (8oC).


• Fiberboard boxes—Load boxes lengthwiseon their bottoms. Most limes are packed in afiberboard box containing 10 pounds, but afew are still shipped in a 4/5-bushel fiber-board box. Load the 4⁄5-bushel boxes in anairflow pattern (figure 10) or palletized 9per layer and 6 layers high. See figure 12 forpallet loading patterns.

Mangoes





Generally, the best transit temperature formangoes is 55oF (13oC). All mangoes arehighly susceptible to chilling injury which ismanifested as a gray scald-like discolorationof the skin often accompanied by pitting,uneven ripening, and poor flavor and colordevelopment. Some varieties are susceptibleto chilling injury below 55oF (13oC). Othervarieties can withstand transit temperaturesdown to 50oF (10oC) before sustaining chill-ing injury. Mangoes ripen slowly at 55oF(13oC).

Recommended Loading Methods:

• Fiberboard boxes—Load boxes lengthwiseon their bottoms in an airflow pattern withunobstructed lengthwise air channels (figure10). Most Florida shippers palletize theirmangoes, and load using the center-load pat-tern (figure 12b).

Melons (Honeydew, Casaba, Crenshaw, Persian)





Melons are very sensitive to chilling injury(pitting and physiological breakdown), andare easily bruised. Temperatures below 45oF(7oC) may result in sunken areas on the skinand eventual decay.

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NOTE: Research has shown that honeydewmelons may be transported at 36o to 41oF(2o to 5oC) if they are treated with 1,000p/m ethylene gas for 24 hours immediatelyafter harvest and then cooled to these tem-peratures. For ethylene gas treatments to beeffective, the melons must be above 70oF(21oC). The gas may be applied before orafter loading for more uniform ripening.

Precool honeydew melons before loading ifthey are extremely hot, over 80oF (27oC).The amount of precooling will depend onthe initial temperature of the melons, theamount of intransit ripening desired and thecapacity of the trailer’s refrigeration system.Many packing sheds ship honeydews ataround 80oF (27oC) to allow some ripeningin transit.

Honeydews have a relatively low respirationrate and are not densely packed. Most mod-ern refrigerated trailers should have thecapacity for intransit temperature pull downprovided the melons are loaded at or belowthe normal 80oF (27oC) shipping tempera-ture, with good air circulation to all parts ofthe load.


• Corrugated fiberboard boxes—Mostmelon boxes are palletized. Five pallet loadpatterns are shown in figure 12. However, ifthe melons require intransit ripening, use thepattern shown in figure 12a to maximize aircirculation in the load. Use an airflow pat-tern (figure 10) for hand-stacked loads.

Mushrooms





Fresh mushrooms are highly perishable witha shelf life of about 1 week under optimumconditions. Prompt precooling after harvest

and close temperature control during transitare essential. Mushrooms are easily bruisedand should be handled carefully. Moisturefrom condensation or other sources shouldbe avoided. Mushrooms are sensitive towater and may develop brown spots anddecay rapidly if wet. Fresh mushrooms maybe prepackaged in 8-, 12-, and 16-ounce(0.23, 0.34, and 0.45 kg) consumer pack-ages, which are then packed in fiberboardtrays. They also may be packed bulk in 10-pound (4.5 kg) fiberboard trays, or in 3-pound (1.4 kg) wooden baskets or fiber-board boxes.


Nearly all mushrooms are palletized forshipment. See figures 12a and b for palletloading patterns.

Okra





Okra deteriorates rapidly and has a veryhigh rate of respiration at warm tempera-tures. Okra has a shelf life of about 10 days.Do not top-ice, because this will cause waterspotting at all temperatures. At temperaturesbelow 45oF (7oC), okra is susceptible tochilling injury which is manifested by sur-face discoloration, pitting, and decay. Okraalso is easily bruised, and bruised areas willblacken rapidly.



• Fiberboard boxes—Load boxes lengthwiseon their bottoms in an airflow pattern (figure10). If palletized, use pallet load patterns(figure 12).

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Onions (green), Shallots, and Leeks




• Highest freezing point:Onions (bunch or spring):

30.4oF (–0.9oC)Shallots (white leaf bare):

31.6oF (–0.2oC)Leeks (blanched stalk):

30.7oF (–0.7oC)

• Top-ice and/or package-ice OK

Green onions and shallots are highly perish-able and should be precooled soon after har-vest. Crushed ice in the package and top-icewill help to retain moisture and crispness,and help reduce yellowing. Do not loadleeks with figs or grapes since these prod-ucts will absorb the leek odor. Odor fromgreen onions is absorbed by corn, figs,grapes, mushrooms, and rhubarb.


• Fiberboard boxes (waxed)—Load boxeslengthwise or crosswise on their bottoms.Load with other commodities that requiretop-icing and leave space between rows ofboxes or pallet loads for top-ice to fill (figure16). If top-ice is not used, hand-stack loadsin an airflow pattern (figure 10) to allowmaximum ventilation. Load palletized boxesin an airflow pattern (figures 12a and 18).

• Wirebound crates—Load crates in thesame way as fiberboard boxes.

Onions (dry bulbs)


• Desired transit temperature:32o-45oF (0o-7oC) storage varieties45o-60oF (7o-15.5oC) fresh varieties



Dry onions store well if held at the propertemperature and humidity and kept dry afterthey are cured. Higher temperatures willcause sprouting and decay. Onions removedfrom cold storage during warm weather tendto sweat on contact with warm humid air.Avoid these conditions by minimizing thetime the onions are on an open dock or load-ing from enclosed docks. Further reducecondensation by precooling the vehiclebefore loading and maintaining adequate aircirculation in the vehicle during transit. Dryonions are packaged in a variety of ways forshipment, including 25- and 50-pound (11.3and 22.7 kg) mesh or plastic bags, 40-pound(18 kg) fiberboard boxes and various sizesof consumer-size mesh and plastic bags inshipping boxes.


• Open mesh or plastic bags—Load bagslengthwise or crosswise on floor or pallets.Load away from the walls and floor inextremely hot or cold weather to preventtemperature damage. Wrap with net or straploads to secure the onions to the pallet. Cen-ter-load the pallets to keep the onions awayfrom the walls in extremely cold or hotweather (figure 12b).

• Fiberboard boxes—Load hand-stackedboxes lengthwise on their bottoms in an air-flow pattern (figure 10). Or load the boxeslengthwise or crosswise on pallets, and loadthe pallets off the wall (figure 12b).

Oranges


• Desired transit temperature:Florida and Texas: 32o to 34oF

(0o to 1oC)California and Arizona: 38o to 48oF

(3o to 9oC)


• Highest freezing point:Peel 29.7oF (–1.3oC)Flesh 30.6oF (–0.8oC)

The preshipment handling of oranges variesby production area and season. Generally,

46

the fruit is washed, waxed, treated, andpackaged for shipment. Most shippers donot precool oranges; therefore, the fruit tem-perature at loading depends on ambient tem-perature. Oranges are precooled in someareas, particularly in California. It is impor-tant to precool oranges prepackaged in poly-ethylene or mesh consumer bags andshipped in master shipping cartons, since thepackaging makes it very difficult to cool intransit.

California and Arizona oranges shipped attemperatures below 38oF (3oC) are suscepti-ble to chilling injury and other rind disor-ders. Oranges from all citrus-producingareas are subject to blue- and green-moldrots. In addition, Florida and Texas fruit aresusceptible to stem-end rot. Losses fromdecay can be reduced by decay inhibitors,careful handling to prevent skin breaks, andproper refrigeration.


• Fiberboard boxes—Load boxes length-wise or crosswise on their bottoms. Loadhand-stacked boxes in an airflow pattern(figure 10). This pattern allows cooling bythe refrigeration system or by ventilation ofoutside air when the ambient temperaturesare reasonably close to the desired transittemperature. Shipments also may be uni-tized on pallets or slipsheets. See figure 12in “Unit or Pallet Loads” for pallet loadingpatterns.

• Bins—Some shippers pack oranges in palletbins constructed of fiberboard, wood, or wiremesh. The oranges may be in bulk or in openmesh bags when packed in the bins. Stackthese bins two-high in the truck. Bin loadingpatterns are the same as for pallets (figure 12).Take care not to block ventilation between thelayers when stacking solid wall bins.

Parsley





• Top- or package-ice desirable

Parsley keeps well at 32oF (0oC) in combi-nation with high humidity. Like all leafyvegetables, parsley has a high rate of respi-ration and its temperature must be loweredquickly to retard respiration and spoilage.Usually parsley is hydro- or vacuum-cooledand top- or package-ice is applied beforeshipment to maintain its crispness. It usuallyis ordered in small lots and shipped inmixed loads with other commodities. Pars-ley is sensitive to ethylene, so do not shipwith ethylene-producing products.


• Fiberboard boxes (waxed) and wireboundcrates—Load boxes and crates lengthwiseon their bottoms. Load in rows across thetrailer with space divided evenly betweenthe rows for top-ice to fill (figure 16). Forpalletized loads, stack the containers length-wise or crosswise on the pallets. Leavespace between the pallet rows and walls fortop-ice to fill (figure 12a).

Parsnips





• Top- or package-ice desirable

Parsnips have transit and storage require-ments similar to carrots. They are toppedafter harvest and will keep up to 4 months ifheld at 32oF (0oC) and a high relativehumidity. Parsnips tend to shrivel from lackof moisture.


• Open mesh or plastic film bags—Parsnipsare usually packaged in plastic film bagsand shipped with ice. Stack bagged

47

parsnips so that when loaded, the parsnipsare in a vertical position. Stack the bags sothat top-ice can infiltrate the load. Baggedparsnips are often palletized and top-iced.In this case, use a pallet loading pattern(figure 12a).

• Fiberboard boxes (waxed)—Hand-stackboxes lengthwise on their bottoms, in regis-ter, in rows across the truck. Divide thespace evenly between the rows for top-ice tofill (figure 16). When palletized, column-stack the boxes in the lower layers to retaintheir strength. Cross-stack the upper layersto stabilize the pallet load. See figure 12 forpallet loading patterns.

Peaches and Nectarines


• Desired transit temperature:31o to 32oF (–0.6o to 0oC)



Peaches and nectarines are relatively tenderfruits and bruise easily. They are usuallyharvested and shipped while still firm, sothat physical injury will be minimized dur-ing transit and marketing. To delay ripeningand retard decay, promptly hydrocool orcool with forced air to the desired transittemperature before loading.


• Corrugated fiberboard boxes—Loadboxes lengthwise on their bottoms. Boxesare usually volume-filled with 25 to 30pounds (11.3 to 17.2 kg) of fruit. Mostshippers unitize their fruit on disposablewooden pallets.

• Wooden or fiberboard lugs—Load lugslengthwise on their bottoms. The fruit isoften packed in plastic trays, in either one ortwo layers, which are then packed in thelugs. The lugs are palletized.

If not precooled, load hand-stacked contain-ers in an airflow pattern (figure 10). Center-load palletized containers (figure 12b).

Pears





Precool pears as soon after harvest as possi-ble to protect their shelf life. The storage lifeof pears ranges from 2 to 8 months, depend-ing on variety. Extensive warming of pearsstarts the ripening process which cannot bereversed. Therefore, transport pears as closeto the storage temperature as possible.


• Corrugated fiberboard boxes—Fiberboardboxes may be volume-filled, place-packed,or tight-filled (vibration settled) with thecover tightly secured with strapping materi-al or staples. The boxes are usually unitizedon disposable wooden pallets and securedby straps or netting. Load patterns for pal-lets are shown in figure 12. For hand-stacked loads, use a tight loading pattern ifthe pears are thoroughly precooled. If thepears are not precooled to near the desiredtransit temperature, load in an airflow pat-tern (figure 10).

Peas (green and snow peas in pods)


• Desired transport temperature:32oF (0oC)


• Highest freezing point:Pods: 30.9oF (–0.6oC)Shelled peas: 29.9oF (–1.2oC)

• Top- or package-ice required

48

Fresh green peas are extremely perishableand require the utmost care to keep them insalable condition. To slow the changing ofsugar to starch, lower and hold the tempera-ture of the peas to near 32oF (0oC) immedi-ately after harvest by vacuum- or hydrocool-ing. Top-ice after loading to help maintain alow temperature and the fresh appearance ofthe pods. With less-than-truckload shipmentsof peas and where top-icing is not feasible,pack the peas with crushed ice. Peas are eth-ylene-sensitive, so do not ship in mixedloads with ethylene-producing products.


• Wirebound crates—Hand-stack crateslengthwise or crosswise on their bottoms.Keep rows aligned, with space divided evenlyin between for top-ice to fill (figure 16).When crates are palletized, use an off-wallpattern (figures 12a and b) which allows max-imum air circulation or top-ice infiltration.

• Fiberboard boxes (waxed)—Pack peas inwaxed fiberboard containers that are well ven-tilated, with holes on all faces. Pack crushedice with the peas. Load hand-stack boxes andpallets the same as wirebound crates.

Peppers (sweet)




Mature-green peppers held at temperaturesbelow 45oF (7oC) will incur chilling injury.Peppers stored at chilling temperaturesdevelop pitting, scald, and various decays. Attemperatures above 55oF (13oC) peppers candecay quite rapidly. Peppers are sensitive toethylene, which will hasten ripening, so donot ship with ethylene-producing products.


• Fiberboard boxes—Load boxes lengthwiseon their bottoms. Hand-stack boxes in anairflow pattern (figure 10). Many shipments

of peppers are palletized. See figure 12 forpallet loading patterns.

Pineapples


• Desired transit temperatures:Mature-green fruit, 50o to 55oF

(10o to 13oC)Ripe fruit, 45oF (7oC)



Mature-green pineapples are susceptible tochilling injury if exposed to temperaturesbelow 50oF (10oC). Symptoms of chillinginjury are impaired ripening, brown or dullshell color, water soaked flesh, wilting of thecrown, green spotting, and failure to developa good flavor. Chilled fruit is particularlysubject to decay if not kept refrigerated.


• Fiberboard boxes—Load boxes lengthwiseor crosswise on their bottoms. Boxes oftenhave fiberboard inserts placed between indi-vidual fruit to prevent bruising during tran-sit. In extremely cold or hot weather, loadboxes in an offset-by-layers pattern (figure7a). This will reduce product contact withthe vehicle walls and possible chilling orfreezing injury, especially if the walls areflat. Center-load pallets away from the wallsin extremely cold weather for the same rea-son (figure 12b).

Plums and Fresh Prunes





Thoroughly precool plums and fresh prunessoon after harvest. Generally, plums and

49

prunes are packed and placed in cold-storagerooms for precooling before shipment. Handlecarefully, because bruising and skin breaksmay result in decay and loss of quality.

Recommended loading method:

• Corrugated fiberboard boxes—Load boxeslengthwise or crosswise on their bottoms. Aconsiderable amount of this fruit is tight-filled (vibration-settled in the boxes with thecover tightly fastened) to reduce fruit bounc-ing and rotation in the boxes from highwayvibration. Fruit movement within the boxesresults in discolored rings in the skin aroundindividual fruit, known as “roller bruising.”Also, some fruit is tray-packed in fiberboardboxes. The boxes then are unitized on dis-posable wooden pallets and secured withstraps or netting material (figure 14). Figure12 shows pallet loading patterns.

Potatoes


• Desired transport temperature:Early crop—for table, 50o to 60oF

(10o to 16oC)—for chipping, 65o to 70oF

(18o to 21oC)Late crop—for table, 40o to 50oF

(4o to 10oC)—for chipping, 50o to 60oF

(10o to 16oC)



Ventilation, heating, or cooling may berequired for potatoes in transit depending onthe time of year and outside temperatureconditions.

Early crop, or new, potatoes are harvestedand shipped from the southern States duringthe winter, spring, and summer. Becausethese potatoes are shipped before their skinhas had time to set or mature, they are easilyskinned and bruised. Broken skins open theway for decay organisms and tissue brown-ing at the surface and lower the market valueof the product. Potatoes, fortunately, have the

inherent ability to seal skin breaks by pro-ducing suberin and wound periderm, whichare essentially new skin. This self-healingprocess proceeds best at a high humidity andtemperatures of 60o to 70oF (16o to 21oC). Ifnewly harvested potatoes are to be in transitfor more than 48 hours, the lower portion ofthis temperature range is recommended.

As a rule, early crop potatoes may beshipped satisfactorily under ventilation. Ven-tilation aids drying when weather permits.Load in an airflow pattern to ensure fullventilation of potatoes packed in fiberboardboxes (figure 10).

Late crop potatoes are harvested during thesummer and fall. They are allowed a longertime to mature before being dug. Therefore,their skins are less prone to injury from han-dling. Because of their tougher skins andless skinning, they do not need the highertemperature and humidity for healingrequired by early crop potatoes.

Most late crop potatoes are grown andstored in the northern States. They areshipped from storage in the late fall, winter,and early spring. Since many shipmentsmove through areas with subfreezing tem-peratures, heat is often needed when trans-porting late crop potatoes. Operate fans withthe heating system to circulate the warmedair around the load.

CAUTION: Take care to vent all directcombustion heaters.

Freezing damage is most likely in bags ofpotatoes loaded directly on the truck floorand against the bottom sidewalls. Cushion-ing or padding material on the floor willhelp insulate the product in the bottom lay-ers, and protect against bruising from over-head weight. However, do not use any mate-rial, such as straw, that will fill the floorgrooves, because it will block warm-air cir-culation under the load. Several types ofsuitable floor padding materials are avail-able from commercial sources. Loadingpotatoes on wood pallets with the stringersrunning lengthwise also provides a means ofprotecting the potatoes from freezing atfloor level by allowing circulating air underthe load.

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Ventilate loads of late crop potatoes whenoutside temperatures range between 40o to50oF (4o to 10oC) by opening the ventdoors. At temperatures below or above thisrange, only open vent doors slightly to avoidoxygen starvation of the load.


• Burlap and master bags—Most potatoesare packed in consumer bags of plastic filmholding 5 or 10 pounds (2.3 or 4.5 kg).These, in turn, are packed in polyethylene orpaper master bags holding 50 pounds (22.7kg) and palletized. Research has found thatpotatoes incur the most loading-related bruis-ing when bags or boxes are dropped on hardfloor or pallet surfaces. Significant increasesin bruising damage were found when thedrop heights exceeded 30 inches (76 cm).

Center-load pallets (figure 12b) in extremecold weather to keep the potatoes away fromthe walls and prevent freezing or chill dam-age. Load hand-stacked bags in a pyramidpattern (figure 7b) to reduce wall contact.

• Corrugated fiberboard boxes—Stack boxeslengthwise or crosswise on their bottoms onthe floor, or unitize on pallets. Hand-stackboxes of new potatoes in an airflow pattern(figure 10c) to allow intransit drying. Loadboxes of potatoes shipped from storage inwinter in an offset-by-layers pattern (figure7a) to reduce contact of potatoes with thewalls and chance of freezing. Center-load pal-letized boxes (figure 12b) for the same reason.

• Bulk potatoes for chipping—Most pota-toes for chipping are shipped from storagein bulk loads. Always load and transport thepotatoes at the same or slightly warmertemperature than the storage temperature,but never at colder temperatures. Handle thepotatoes as gently as possible. Rough han-dling and improper temperatures may causeadverse chemical reactions which mayincrease the sugar content of the potatoes.This subsequently results in undesirabledark-colored chips. Truckers should carryan accurate thermometer for checking pulptemperatures of the potatoes. Bulk chippingpotatoes usually are loaded with a bin-pilerconveyor with a telescoping boom. Theyare unloaded with an industrial truck or by

gravity flow.

Construct bulkheads of plywood or placebags of potatoes 2 to 4 feet (0.6 to 1.2 m)from the rear doors of the trailers to containthe loose potatoes. Place heaters in this openspace, when required.

Chipping potatoes shipped from far northernStates in the winter require heating. Temper-ature controlled semi-trailers are preferredand predominantly used. If heaters are used,operate the fans at all times to circulate theheated air over and under the load.

A buildup of carbon dioxide (CO2) anddepletion of oxygen (O2) may also result inoff-colored chips. Therefore, allow a smallamount of outside air to ventilate to thechipping potatoes at all times. Operate thefan to circulate fresh air to all parts of theload. Chipping potatoes should be processedas soon as possible after unloading.

Radishes





• Top- or package-ice OK

Precool radishes to remove field heat andpreserve natural crispness. Most radishes aretopped and packed in consumer-size plastic-film packages which are shipped in waxed,corrugated fiberboard boxes. Some radishesare shipped with their tops on and to keepthem fresh, these radishes must have top-iceor package-ice placed in the containers.Topped radishes packed in consumer bagskeep well in transit and storage for severalweeks, provided the recommended tempera-ture and humidity are maintained. Blackspotting is a major market disease of radish-es, but temperatures below 50oF (10oC) con-trol it effectively.


• Waxed fiberboard boxes (consumer pack-

51

ages)—If shipping a straight load of radish-es, hand-stack boxes in an airflow pattern(figure 10) to allow uniform circulation ofrefrigerated air throughout the load.

• Wirebound crates or fiberboard boxes(bunches with tops)—Load crates or boxeslengthwise on their bottoms. Keep rowsaligned, evenly dividing the space betweenthem for top-ice to fill (figure 16).

• Polyethylene bags (bulk radishes)—Bagged radishes are usually shipped stackedon pallets. See figure 12 for pallet loadingpatterns. For top-iced loads, use the loadpattern in figure 12a which leaves spacebetween the pallet rows and the walls fortop-ice to fill.

Raspberries




• Highest freezing point:black—30.0oF (–1.1oC)red—30.9oF (–0.6oC)

Fresh raspberries soften and decay rapidly.Under the very best conditions their marketlife is 7 to 10 days. Transcontinental truckshipments of red raspberries from Californiaare common. These shipments are usuallypalletized and in mixed loads with strawber-ries, which have similar packaging and tran-sit requirements. Raspberries are subject tovarious types of mold, which can be con-trolled most effectively by rapidly precool-ing and holding the berries at the desired32oF (0oC) temperature immediately afterharvest. For additional protection againstdecay and ripening during transit, majorshippers enclose the pallet loads of berriesin air tight plastic bags and inject an atmos-phere modified with 10 to 20 percent carbondioxide (CO2).

Recommended loading method:

• Corrugated fiberboard trays—Load trays

lengthwise on bottoms. Trays of berries usu-ally are palletized to minimize handling.Strap the trays securely to the pallets to min-imize bouncing and rotating of the berriesfrom highway shock and vibration, a majorcause of physical damage to berries duringtransit. Center-load the pallets and braceaway from the walls so that air can circulatebetween the walls and the product (figure12b).

Rhubarb




• Highest freezing point, stalks:30.3oF (–0.9oC)

Keep fresh rhubarb at 32oF (0oC) and at ahigh humidity to prevent wilting and shriv-eling. Bunches or loose stalks of rhubarb areusually wrapped in polyethylene film linersbefore packing in shipping boxes to preventmoisture loss. Do not seal the liners, andensure the boxes or crates are well vented toallow refrigerated air to remove respirationheat and prevent mold development.


• Fiberboard boxes—Load boxes lengthwiseor crosswise on pallets. Load hand-stackedboxes lengthwise on their bottoms in an air-flow pattern (figure 10). See figure 12 forpallet loading patterns.

Romaine Lettuce


• Recommended transit temperature:32oF (0oC)

• Recommended relative humidity:95 percent


Romaine is a highly perishable, leafy veg-etable requiring maximum refrigeration dur-

52

ing transit. Vacuum-cool or hydrocoolbefore shipment, depending on the shipper’sfacilities. Romaine is often shipped in mixedloads, because most orders are for less-than-truckload lots. It is packed both loose and inplastic bags in fiberboard boxes. Romaine issensitive to ethylene gas, so do not ship withethylene-producing products.


• Fiberboard boxes (waxed)—Load boxeslengthwise on their bottoms. Load hand-stacked boxes in an airflow pattern (figure10). Center-load palletized boxes, or use anairflow pattern to keep the product awayfrom the walls of the vehicle (figures 12aand b).

Salad Mixes


• Recommended transit temperature:33oF (0.6oC)

• Recommended relative humidity:90 to 95 percent

• Highest freezing point:Varies by commodity components (referto individual commodity)

Prepackaged salad mixes are one of thefastest growing segments of the produceindustry. Salad mixes may contain a widevariety of vegetables, but the primary com-ponents are usually lettuce, cabbage, andother leafy greens. The mixes are usuallyvacuum-packaged in plastic film bags andshipped in fiberboard boxes. A number ofshippers also inject a mixture of gases ormodified atmosphere into the film packagewhich is custom-formulated to extend theshelf life of the particular mix of vegetablesin the salad. To obtain a maximum shelf lifeof 10 to 14 days for salad mixes, maintainthe desired transit temperature. Also, do notpuncture the film bags during handling,which may allow the introduction of ethyl-ene gas and result in russeting and yellow-ing of the salad components.


• Fiberboard boxes—Load boxes lengthwise

or crosswise on pallets. Secure the boxes tothe pallets to prevent handling damage tothe bags and salad leaves, and use an off-wall loading pattern (figures 12a and b).Load hand-stacked boxes in an airflow pat-tern (figure 10).

Spinach





• Top-ice and/or package-ice desired

Fresh spinach is delicate and highly perish-able. Handle carefully to prevent damageto the leaves which presents a potentialpoint for disease entry. Precool freshspinach immediately after harvest, holdnear 32oF (0oC), and pack with ice to pre-vent wilting and preserve its shelf life ofabout 10 to 14 days. Spinach is sensitive toethylene, so do not ship with ethylene-pro-ducing products.


• Wirebound crates or waxed fiberboardboxes—When top-iced, load hand-stackedcrates or boxes lengthwise on their bottomsin straight rows. Divide space evenlybetween the rows for top-ice to fill (figure16). Stack waxed fiberboard boxes directlyon top of each other so melt-water can rundown through the stack. If not top-iced, loadcrates or boxes in an airflow pattern (figures10 and 11).

• Fiberboard boxes—Spinach is oftenpacked in plastic film consumer packs, andthen in fiberboard boxes. For hand-stackedboxes, load in an airflow pattern (figure 10).Stack palletized boxes of consumer packs inregister, and secure with strapping to pre-vent bruising of the tender leaves. Figures12a and b show the recommended palletloading patterns.

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Squash and Pumpkins


Winter squash (Hubbard and acorn) andpumpkins




Summer squash (yellow crookneck, straight-neck, and zucchini)

• Desired transit temperature41o to 50oF (5o to 10oC)

• Desired relative humidity95 percent


After harvest, allow winter squash andpumpkins to cure at temperatures between80o and 85oF (27o to 29oC) for 10 to 20 daysto allow healing of mechanical cuts. Curedsquash have a storage life of 2 to 6 months.However, they are subject to chilling injury,so do not keep or ship them at temperaturesbelow 50oF (10oC) for any length of time.They also require low humidity.

Summer squash are harvested and shipped atan immature stage. They are more perish-able than winter squash. Their storage life isshorter, and they require lower temperaturesand higher humidity during transit. The skinof summer squash is very tender and easilywounded during handling. Summer squashis chilling-sensitive but can withstand 32o to40oF (0o to 4oC) temperatures for up to 2days with little danger of chilling injury.


• Wirebound crates—Load crates of summersquash lengthwise on their bottoms in an air-flow pattern (figure 10). Crates of wintersquash may be tightly stacked either length-wise or crosswise on bottoms. Stack wire-bound crates in vertical alignment and never

allow them to cross over each other, becausethey are not designed to bear overheadweight on their sidewalls. When palletized,stack the crates in vertical alignment andstrap securely to the pallet. Center-load thepallets away from the walls (figure 12b),unless the walls are ribbed to allow air circu-lation.

• Fiberboard boxes—Load fiberboard boxesof winter squash crosswise or lengthwise ontheir bottoms. Load hand-stacked boxes ofsummer squash in an airflow pattern (figure10). Center-load palletized boxes (figure 12b).

• Bulk-bins—Pumpkins often are shipped inbulk bins. If the bins are double stacked,take care not to over fill the bins on the bot-tom layer, or pumpkins will be crushed.

Strawberries





Strawberries are extremely perishable andrarely keep more than 10 days under idealconditions. Temperatures near 32oF (0oC)are essential to control decay and ripening.Precool strawberries immediately after har-vest to as close to 32oF (0oC) as possible.

Most California shippers palletize theirstrawberries. In some cases, they place asealed plastic bag around each pallet loadunit, filled with a modified atmosphere con-taining about 14 percent CO2 gas to assist inretarding decay and ripening.

Strawberries are highly susceptible to decayby fungal rots and molds. Ship only soundfruit, because decay fungi are easily spreadthroughout the shipping container. Handlestrawberries very carefully, since they areeasily bruised. Bruised berries are very sus-ceptible to decay.


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• Open-top fiberboard tray boxes—Nearlyall strawberries are shipped in tray boxeswhich are designed to interlock by wires ortabs when stacked in register. Load hand-stacked trays in rows lengthwise on theirbottoms and stabilize every fourth layer withwood strips placed horizontally across thetruck.

Secure palletized loads with strapping toprevent the trays of berries from bouncing.Highway shock and vibration is a majorcause of intransit abrasion and bruising.Take extreme care to load and brace the pal-lets to prevent intransit shifting. Center-loadthe pallets off the walls to prevent heat con-duction from the trailer walls to the fruit(figures 12a and 17).

Sweet Potatoes





Sweet potatoes are harvested in late summeror early fall. Some are shipped immediatelyto market in the “green” state, noncured.The rest are cured and shipped from storagethroughout the year. They are washed, sort-ed, and sometimes treated with a decay pre-ventive before being shipped to market.Also, many shippers wax sweet potatoes anddye them red.

Uncured sweet potatoes require careful han-dling to prevent skin breaks and decay.Cured sweet potatoes are easier to handle.Sweet potatoes are subject to chilling injuryat temperatures below 50o F (10oC), even ifonly for a few hours, which may impairtheir appearance, taste and texture. Sprout-ing may occur at temperatures above 60oF(16oC), and temperatures above 70oF (21oC)may cause decay.Sweet potatoes are predominantly shipped infiberboard boxes containing 50 pounds (23kg); however, some are packed in smaller

fiberboard boxes, and some are packed inwirebound crates, or bags.


• Fiberboard boxes—Load boxes lengthwiseon their bottoms. Load hand-stacked boxesin an airflow pattern (figure 10). See figure12 for pallet loading patterns.

Tangerines



• Desired relative humidity90 to 95 percent


Tangerines are highly perishable. Duringmarketing they are very susceptible todecay, particularly green- and blue-moldrots. Careful handling from tree to tablehelps to prevent bruising and skin breaksthat provide ready entrance for decay organ-isms. Other citrus varieties, such as tangelosand honey tangerines (Murcott), are thin-skinned and need careful handling. Most ofthese varieties can be shipped at near 32oF(0oC) during domestic transit periods ofseveral days. However, ship Temple orangesand Orlando tangelos at 40oF (4oC),because they are susceptible to chillinginjury at lower temperatures. Precool tan-gerines before shipping.


• Fiberboard boxes—Load boxes lengthwiseon their bottoms in an airflow pattern (figure10). See figure 12 for pallet loading pat-terns.


Tomatoes (mature-green)


• Desired transit temperature:

55

55o to 70oF (13o to 21oC)


• Highest freezing point:31oF (–0.6o)

Mature-green tomatoes are harvested in thegreen stage and are washed in chlorinatedwater, graded, and packed immediatelyafter harvest. After packing, some toma-toes are placed in ethylene degreeningrooms at 70oF (21oC) for about 48 to 72hours to initiate ripening. Most go throughthis process at wholesale marketing facili-ties. After ethylene degreening, the besttemperatures for transport and storage oftomatoes are between 55o and 70oF (13o to21oC). At temperatures lower than 50oF(10oC) mature-green tomatoes may incurchilling injury and be of poor internalquality. At temperatures above 70oF(21oC), tomatoes may ripen too rapidlyand decay extensively.


• Fiberboard boxes—Most tomatoes areshipped in partial telescope fiberboardboxes. Load hand-stacked boxes in an air-flow pattern (figure 10). Most shippers pal-letize their shipments. See figure 12 for pal-let loading patterns.

Tomatoes (pink)





Tomatoes harvested soon after their colorbegins to redden are called pink, or “vine-ripened” tomatoes. Pink tomatoes are notas sensitive to chilling injury as maturegreen fruit. Handle pink tomatoes carefullyto avoid mechanical injury. External andinternal bruising may affect appearance,color, or flavor. Shipping temperatures forpink tomatoes will depend largely on the

number of days in transit and the degree ofripeness which the receiver may desire.Many shippers precool their pink tomatoesto the transit temperature which will main-tain the desired color level. Pink tomatoesare generally packed in fiberboard boxeswith two or three layers per box. Someshippers pack their pink tomatoes in pulpor foam trays.


• Fiberboard boxes—Load hand-stackedboxes lengthwise on bottoms in an airflowpattern (figure 10). Most shippers palletizetheir tomato loads. See figure 12 for palletloading patterns.

Watermelons


• Recommended transit temperature:50o to 60oF (10o to 16oC)

• Recommended relative humidity:90 percent


Watermelons are generally shipped in bulkunder ventilated conditions. In moderateweather, refrigeration normally is notrequired for transit periods of a few days.Improve flavor and intensify color by hold-ing watermelons up to 7 days at room tem-perature. However, if the melons are to be intransit for longer than 1 week, they should berefrigerated in the 50o to 60oF (10o to 16oC)range. At temperatures between 32o to 50oF(0o to 10oC), watermelons are subject tochilling injury which may include pitting,off-flavors, and color loss. Watermelons alsoare sensitive to ethylene, so do not ship withethylene-producing products. Serious transitlosses may result when watermelons arecracked and bruised by improper handlingand loading. Bruising makes the melonsmore susceptible to decay. When loadingbulk melons, place cushioning material onthe trailer floor to protect them. Varioustypes of cushioning materials are available,such as excelsior, polystyrene foam, straw,etc. Although straw is commonly used, it isnot recommended in trailers with floor

56

grooves because it blocks air circulationunder the load and fills desired spacesbetween the melons.


• Bulk—The greater percentage of watermel-ons are shipped in bulk. Load both the long-type and round-type melons in rows parallelto the sidewalls of the trailer. Even-num-bered layers will hold one less melon thanodd numbered-layers. The number of layersin a particular load will depend on theweight of the trailer, highway weight limita-tions, and the quality of the watermelons.

• Fiberboard boxes—Fiberboard boxes maycontain two to six watermelons. Load theboxes lengthwise on their bottoms, one boxdirectly on top of another, and either 4 or 5boxes wide, depending on size of the trailerand boxes. Divide slack space across thewidth of the trailer evenly between the rows,providing lengthwise air channels betweeneach row. Fiberboard boxes of watermelonsare frequently palletized. See figure 12 forpallet loading patterns.

• Bulk bins—Bulk bins of watermelons onpallets may weigh from 800 to 1200 pounds(363 to 554 kg). Stack the bins two-high in

57

the trailer. To prevent crushing, put fewermelons in the lower bin. See figure 12 forpallet loading patterns.

Damage claims for canned goods cost carri-ers millions of dollars annually. There aretwo major causes of damage to cannedfoods during distribution—mechanical andtemperature. Improper handling causesmechanical damage, dented or broken cansand bottles, and is responsible for the great-est percentage of claims. A smaller percent-age of the claims results from improper tem-perature conditions, which cause rusting ofthe cans or freezing of the contents.

Damage is caused to canned goods in manyways, such as:

• poorly sealed cases;

• careless handling of cans during process-ing and warehousing;

• improper stacking on pallets;

• careless handling with mechanical-lifttrucks;

• loose or slack loading in the vehicle;

• improper bracing, wrapping, or strapping;and

• failure to brace remainder of the load aftera dropoff.

Poorly sealed cases may let cans or jars fallout during handling. Check cases of cannedgoods periodically during loading for indica-tions of damage. Do not accept a heavilydamaged load.

Currently, most canned goods are unitized

for warehousing and shipment. Mishandlingof pallets with mechanical-lift trucks andpoor stacking of cases on the pallets areimportant sources of damage. Stack thecases so that they are flush with the edges ofthe pallet. If the cases overlap the edges ofthe pallet, lift trucks may push against thecanned goods instead of the pallet duringhandling. If there is a space between the out-side edges of the stack and the pallet edges,considerable slack space may be leftbetween the pallets after they are loaded inthe vehicle. This may allow the cases toshift during transit.

Another source of damage is loose palletboards. A loose edge board will allow pres-sure to be exerted on the cases in the bottomlayer, when the pallet is lifted with a fork lifttruck. Keep pallets in good repair at alltimes.

A large percentage of the unit loads ofcanned goods are stretch- or shrink-wrappedwith plastic film before shipment. Thisassures integrity of the pallet loads andreduces damage claims.

Tight loading is important, whether the ship-ment is unitized or hand-loaded. Any slackspace that lets the cases shift or fall mayresult in damaged goods. Load the cases orpallet units snugly together, and brace theend of the last stack. In a split shipment,brace and block the end of the last stackbefore moving to the next dropoff. Usespacers or inflatable dunnage to fill outcrosswise slack. All pallets or stacks shouldbe the same height, unless precautions aretaken by bracing or otherwise, to prevent theuneven top layer from shifting.Truck drivers cannot control all damage that

Canned Foods

58

may occur before and during loading. How-ever, they can reduce the chances of beingblamed for damage beyond their control bybeing alert for damaged goods and notaccepting them. They also can control thedamage by closely supervising the loadingof their vehicles. A good slogan for haulersof canned goods is, “The only right load is atight load.”

The most frequent type of temperature dam-age to canned foods is rusting of tin cans.Rusting is caused by condensation on cansremoved from a low-temperature environ-ment to one with a higher temperature. Con-densation causes rust spots on the cans andwrinkling of the labels and may make theproduct unmarketable. Also, after a periodof storage, the rust spots may pinhole thecans with leaks and allow the product to

spoil. To prevent rust-causing condensation,do not unload canned foods in warm ware-house areas which have previously beensubjected to low temperatures, until theyhave had time to warm up to 50oF (10oC) orabove.

Freezing is not likely to damage the cannedfood product itself. However, freezing acanned product may endanger the containerintegrity or break a glass container. To pro-tect canned food containers against freezingdamage during transit through areas ofintense cold, apply thermostatically con-trolled heat to keep the product from freez-ing. See table 4 for the freezing points ofsome canned foods.

Extended exposure of canned foods to 90oF(32oC) or above temperatures is detrimentalto product quality. In some cases, exposure

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Table 4. Freezing Temperature of Selected Canned Foods

FreezingPoint

Product oF oC

Applesauce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.6 (–2.4)Asparagus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30.2 (–1.0)Beans, green stringless . . . . . . . . . . . . . . . . . . . . . . . . . . 30.3 (–0.9)Beans, lima . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.6 (–1.3)Beans, with pork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.8 (–1.8)Beans, strained . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30.6 (–0.8)Beans, wax, cans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30.3 (–0.9)Beans, wax, glass jars . . . . . . . . . . . . . . . . . . . . . . . . . . . 30.2 (–1.0)Beets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30.4 (–0.9)Carrots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30.3 (–0.9)Catsup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.4 (–7.0)Chili sauce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.7 (–4.6)Corn, creamed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.6 (–1.3)Corn, in brine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.4 (–1.4)Corn, vacuum-packed . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.7 (–1.3)Cranberry sauce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.3 (–8.7)Grapefruit juice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30.2 (–1.0)Milk, evaporated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.4 (–1.4)Mushrooms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.8 (–1.2)Peaches, heavy syrup . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.6 (–1.9)Peaches, light syrup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.6 (–2.4)Pears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.6 (–2.4)Peas, Alaska . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.0 (–0.6)Peas, sweet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.3 (–1.5)Pea soup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.7 (–2.4)Potted meat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.0 (–3.3)Pumpkin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30.7 (–0.7)Salmon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.2 (–2.7)Sardines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.2 (–2.1)Spiced meat . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.2 (–5.4)Spinach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30.8 (–0.7)Succotash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.9 (–1.2)Sweet potatoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.2 (–1.6)Tomatoes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30.8 (–0.7)Tomato juice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.8 (–1.2)Tomato soup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.4 (–2.6)Tuna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.3 (–3.2)Vinegar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.7 (–1.8)

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to these higher temperatures may result intotal product loss through thermophylicspoilage.

Butter and Margarine


• Desired transit temperature:Butter (fresh), 39oF (4oC)Butter (frozen), –10oF (–23oC)Margarine, 35oF (2oC)

• Desired relative humidity:Butter, 75 to 85 percentMargarine, 60 to 70 percent

Butter and margarine usually are shippedfrom cold storage and are at the desired tran-sit temperature when loaded. They arepacked in fiberboard boxes that providesome insulation and allow the product to beexposed to room temperatures for short peri-ods during loading and unloading withoutthe risk of serious damage. However, duringshipment the products must be refrigerated atthe recommended temperatures to preventsoftening and quality deterioration. Butterand margarine absorb odors very easily.Trucks or trailers previously used for haulingodorous products, such as fish, cabbage, oronions, should be well cleaned and airedbefore being loaded with butter or margarine.See section II “Cleaning and Sanitation” forhints on removing odors from trailers.


• Fiberboard boxes—Load boxes eithercrosswise or lengthwise on their bottoms onpallets or the truck floor. If the products areat the desired transit temperature when

loaded, stack the boxes as tightly together aspossible to retain that temperature.

In hot weather, take care to prevent heatconducted through the walls and floor frommelting the product. To prevent this, providespace for refrigerated air to circulate aroundthe perimeter of the load. Some vehicles areequipped with deep channel floors andribbed walls for this purpose. If not, attachspacer strips vertically to the interior side-walls to provide air space between the prod-uct and the walls. For hand-stacked loadsplace pallets on the floor with the stringersrunning lengthwise to allow air circulationunder the load. Center-load pallets (figure12b).

Cheeses




• Highest freezing point:Variable by variety. Also, freezing mayresult in textural changes; see text.

Cheeses need to be protected from heat andcold. Most cheeses tend to “oil off” at 68oF(20oC) and above. During oiling off, the fatleaks from the body, and the cheese quicklybecomes rancid.

On the other hand, subjecting some types ofcheeses to freezing temperatures will resultin texture changes that may not be accept-able to consumers. As a general rule, cheeseshould not be held at temperatures below30oF (–1oC) or above 50oF (10oC).

Dairy Products

61

The recommended temperatures for trans-porting and holding some common types ofcheeses are shown in table 5.


• See previous entry, “Butter and Mar-garine.”

Ice Cream


• Desired transit temperature:–20o to –15oF to (–29o to –26oC)

To maintain top quality, ice cream must bekept at the desired transit or holding temper-

ature. It also is very important to keep thetemperature of ice cream constant duringloading and unloading. Fluctuating tempera-tures cause the ice crystals in ice cream toincrease in size. Frequent temperature fluc-tuations will increase the crystal size to thepoint where the ice cream is no longeracceptable to the consumer.

Trucks used for hauling ice cream should bebuilt specifically for that purpose, or meetthe Refrigerated Transportation Foundation’s(RTF) combined equipment DF (deep frozenor –20oF) rating. RTF-certified trailers willhave the equipment rating posted at severallocations on the exterior of the trailer and onthe refrigeration unit (figure 8).

Table 5. Ideal Temperatures for Transporting Common Types of Cheese (fromASHRAE Handbook—Refrigeration)

Ideal TransitCheese Temperature

oF oCBrick . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 to 34 -1.1 to 1.1Camembert . . . . . . . . . . . . . . . . . . . . . . . . . . 30 to 34 -1.1 to 1.1Cheddar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 to 34 -1.1 to 1.1Cottage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 to 34 -1.1 to 1.1Cream . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 to 34 0.0 to 1.1Limburger . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 to 34 -1.1 to 1.1Neufchatel . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 to 34 0.0 to 1.1Process American . . . . . . . . . . . . . . . . . . . . . 40 to 45 4.4 to 7.2Process brick . . . . . . . . . . . . . . . . . . . . . . . . . 40 to 45 4.4 to 7.2Process Limburger . . . . . . . . . . . . . . . . . . . . 40 to 45 4.4 to 7.2Process Swiss . . . . . . . . . . . . . . . . . . . . . . . . 40 to 45 4.4 to 7.2Roquefort . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 to 34 -1.1 to 1.1Swiss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 to 34 -1.1 to 1.1Cheese foods . . . . . . . . . . . . . . . . . . . . . . . . . 40 to 45 4.4 to 7.2

62


• See “Frozen Foods.”

Meat products are highly perishable, andgrowth of microorganisms inherent on meatcarcasses is a major cause of deterioration.Proper refrigeration is necessary to retardthe growth of these microorganisms and pre-serve the fresh physical appearance of themeat products. Dehydration also affects theappearance and marketability of fresh meat.Table 6 gives the recommended tempera-tures and humidities for transporting somefresh meat, seafood, and processed meatproducts.

Fresh meats absorb odors readily, so do notload in vehicles retaining strong residualodors from other products. Do not shipmeats in mixed loads with strong odor-pro-ducing products, such as fish, apples, oronions.

Boxed MeatsIn the United States, nearly all meat animalcarcasses are broken into wholesale or retailcuts, film packaged, and packed in corrugat-ed fiberboard boxes before shipment. Mostwholesale beef cuts are vacuum packaged inplastic film. If not vacuum-packed, cuts areusually individually wrapped before boxingor packed in a plastic bag liner inside theboxes. The packaging materials greatlyreduce the chance of microbial contamina-tion and dehydration of the meat duringtransport. However, the insulating effect ofthe boxes and packaging film make it imper-ative that the meat be at the desired transittemperature when packed and loaded. It will

be difficult for the truck’s refrigeration sys-tem to remove any heat remaining in themeat due to the packaging insulation.


• Fiberboard boxes—Since meat does notproduce respiration heat, stack the boxestightly together, if the meat is at the correcttransit temperature when loaded. The sameprinciple applies here as applies to frozenfoods. Keep a blanket of cold air circulatingaround the load to absorb the heat penetrat-ing the walls and floor of the trailer. If thetrailer does not have ribbed walls, in hotweather load the boxes in a cross-wise offsetpattern (figure 7a) to reduce contact of theload with the walls. Use a trailer with a deepchannel floor, or provide pallets or floorracks with 2 inches (5 cm) or more space forair circulation under the load. In trucks withoverhead air delivery, leave 4 inches (10cm) of space between the load and the reardoors to assure adequate air circulation.Center-load palletized boxes (figure 12b).

Carcass MeatsSince carcass meats may not be protected bypackaging, take extra precautions to protectthe carcasses from additional contaminationby unsanitary handling, dirt, and strongodors. The interior of the vehicle must beconstructed of or coated with materialsapproved for contact with meat by theUSDA’s Food Safety and Inspection Service(FSIS). See section VI, “Regulatory Consid-erations for Truck Construction Materials,Cleaning Compounds, and Sanitary FoodTransport.”

Keep all interior surfaces of the truck in

Fresh and Cured Meat and Fresh Seafood

63

Table 6. Recommended Temperatures and Humidities for Protecting SelectedFresh, Cured, and Processed Meat and Seafood Products During Transit(from ASHRAE Refrigeration Handbook)

RelativeCommodity Temperature Humidity

oF oC PercentFresh meats:

Beef . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 to 34 0.0 to 1.1 88 to 92Lamb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 to 34 0.0 to 1.1 85 to 90Pork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 to 34 0.0 to 1.1 85 to 90Poultry . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 to 32 –2.2 to 0.0 85 to 90Rabbits . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 to 34 0.0 to 1.1 90 to 95Veal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 to 34 0.0 to 1.1 90

Cured and processed meats:Bacon:

Cured, farm style . . . . . . . . . . . . . . . . . . 61 to 64 16.0 to 18.0 85Cured, packer style . . . . . . . . . . . . . . . . . 34 to 39 1.0 to 4.0 85

Dried beef (chipped) . . . . . . . . . . . . . . . . . 50 to 59 10.0 to 15.0 15Frankfurters . . . . . . . . . . . . . . . . . . . . . . . . 32 0.0 85Hams:

Light cure . . . . . . . . . . . . . . . . . . . . . . . . 37 to 41 3.0 to 5.0 80 to 85Country cure . . . . . . . . . . . . . . . . . . . . . . 50 to 59 10.0 to 15.0 65 to 70

Pork Sausages (links or bulk country and Polish) . . . . . . . . . . . . . . . . 32 0.0 85

Fresh fish:Haddock, Cod, Perch . . . . . . . . . . . . . . . . . 31 to 34 -0.6 to 1.1 95 to 100Hake, Whiting . . . . . . . . . . . . . . . . . . . . . . 32 to 34 0.0 to 1.1 95 to 100Halibut . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 to 34 -0.6 to 1.1 95 to 100Herring:

kippered . . . . . . . . . . . . . . . . . . . . . . . . . 32 to 36 0.0 to 2.2 80 to 90smoked . . . . . . . . . . . . . . . . . . . . . . . . . . 32 to 36 0.0 to 2.2 80 to 90

Mackerel . . . . . . . . . . . . . . . . . . . . . . . . . . 32 to 34 0.0 to 1.1 95 to 100Menhaden . . . . . . . . . . . . . . . . . . . . . . . . . 34 to 41 1.1 to 5.0 95 to 100Salmon . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 to 34 -0.6 to 1.1 95 to 100Tuna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 to 36 0.0 to 2.2 95 to 100

Shellfish:Scallop meat . . . . . . . . . . . . . . . . . . . . . . . 32 to 34 0.0 to 1.1 95 to 100Shrimp . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 to 34 -0.6 to 1.1 95 to 100Lobster (American) . . . . . . . . . . . . . . . . . . 41 to 50 5.0 to 10.0 In sea waterOyster, clams

(meat and liquid) . . . . . . . . . . . . . . . . . . 32 to 36 0.0 to 2.2 100Oyster in shell . . . . . . . . . . . . . . . . . . . . . . 41 to 50 5.0 to 10.0 95 to 100

64

good repair. Broken places in the wall andfloor harbor dirt and are difficult to keepclean. Replace faulty or missing door gas-kets and missing floor-drain caps to preventdirt and dust from being sucked in the vehi-cle as it moves over the highway. Keep meathooks and rails free of corrosion or rust that

could work loose and fall on the carcasses.

Before loading, clean and inspect trucks,pallets, and meat hooks used for hauling car-casses. The wash water should be at least180oF (82oC) to reduce the number ofmicroorganisms present and to dissolve fatparticles adhering to the interior surfaces.

Figure 19. Side (a) and end (b)views of a mixed load ofhanging forequartersand hindquarters ofbeef.

(a)

(b)

65

Any sanitizing agents must be approved forcleaning meat equipment by the USDA’sFSIS.

In warm weather, precool trucks haulingmeat carcasses before loading to preventmoisture from condensing on cold carcassesas they are loaded from refrigerated storage.Condensation creates conditions favorablefor the growth of slime-forming microorgan-isms on the meat. Moisture also will con-dense on cold carcasses when doors areopened for delivery stops in warm weather.If at all possible, all loading and unloadingshould be in refrigerated areas.


There are many methods for loading carcassmeats in trucks. Usually quarters of beef arehung by metal hooks on overhead rails. Theforequarters are hung with long hooksinserted through the inside of the rib cavity,usually between the 4th and 5th ribs about11 inches from the backbone, so the quarterswill balance and hang straight. Hindquartersare hung with short hooks, the hook beinginserted through the opening in the gambrelcord of the shank. Figure 19 shows a load ofhanging beef.

Sometimes, both frozen and fresh meat car-casses are loaded stacked like cordwood onthe floor of the truck, or on pallets which arein turn loaded on the truck. In these cases,place clean wrapping paper or plastic filmapproved by the FSIS between the truckfloor or pallet base and the meat, and also

66

between the meat and the truck walls.

Frozen foods should be kept at 0oF (–18oC)or lower from the time they are first frozenuntil readied for consumption, according tothe code of “Frozen Food Handling andMerchandising” available from the FrozenFood Roundtable. The “Roundtable” repre-sents the major trade associations of thefrozen food industry.

Fluctuating temperatures during distributiondegrade the market quality of frozen foods.Recooling frozen foods to the thermostat setpoint after even a slight temperature risecauses moisture to migrate from the productto the colder surfaces of the packagingmaterials. This results in product dehydra-tion and undesirable frost buildup inside thepackages. Product quality losses willincrease with the amount of temperature riseand frequency of recooling.

Frozen foods thaw between 15oF and 32oF(–9o and 0oC). Although the changes are noteasily recognized, even at temperatures aslow as 0oF (–18oC), frozen foods may dete-riorate from fat oxidation and enzymaticchanges. Certain microorganisms also maydevelop at temperatures around 20oF (–7oC)and above, adding to deterioration and cont-amination of the food. The higher the tem-perature, the greater the rate of deterioration.

Ensure that trucks transporting frozen foodare:

• clean and free from dirt, debris, odors, orany substance that may contaminate thefood;

• constructed, insulated, and equipped withadequate refrigeration capacity and air deliv-ery system to continuously maintain a prod-uct temperature of 0oF (–18oC) or colder.(Trailers certified by the Refrigerated Trans-portation Foundation (RTF) will have acombined equipment rating of “F” forfrozen foods on the certification plates post-ed at various locations on the vehicle (seefigure 8); and

• precooled by setting the thermostat at 0oF(–18oC) and letting the refrigeration unitoperate for at least one-half hour beforeloading, or until a temperature gradient isestablished across the insulation. Be sure toschedule adequate time for precooling inwarm weather.

Load boxes of frozen foods in a solid block,avoiding contact with the walls. Ensure thatair refrigerated at or below 0oF (–18oC) cir-culates around all sides of the load to pre-vent the transfer of heat through the trailerto the frozen product (figure 4). Floor chan-nels, floor racks, or pallets 2-1/4 inches (6cm) or more deep will facilitate air circula-tion under the load.

Provide at least 4 inches (10 cm) of spacebetween the load and the rear doors to let airflow freely around the rear of the load. Forvehicles without ribbed walls, attach verticalstripping (1 or more inches thick) on thesidewalls to facilitate air circulationbetween the walls and load. Leave at least10 inches (25 cm) of space between the ceil-ing and the top of the load for unobstructedairflow over the load.

A great deal of frozen food is shipped onpallets or slipsheets. Center-load pallets (fig-ure 12b), and block or brace the load to keep

Frozen Foods

67

the product from toppling against the walls.

If supplemental or emergency refrigerationis needed for a frozen food shipment, placesolid carbon dioxide (CO2) in the form ofdry ice or snow on top of the load. Keep thefans running at low speed to uniformly dis-

tribute cool air around the load.

WARNING: The gas CO2 may causeasphyxiation. Vent the vehicle properly

before entering.

Poultry (fresh and hard-chilled)


• Desired transit temperatures:Fresh, 26o to 34oF (-3o to 1oC)

Hard-chilled, 0oF to 26oF (–18o to –3oC)


• Average freezing point:27oF (–3oC)

Fresh poultry is shipped by two methods,fresh and hard-chilled. After the birds aredressed, they are chilled to 40oF (4oC) orlower. At this point they may be packed inbins, boxes, or crates, with or without ice,and shipped for further processing or forimmediate retail. Fresh poultry has a rela-tively short shelf life of a week or so at most.

Hard-chilled poultry has a shelf life of sev-eral weeks if it is cooled to below 26oF (-3oC) soon after slaughter. The low tem-perature assures cell contraction and reducestissue weepage. Most hard-chilled poultry isbroken into retail cuts and packaged in foamtrays overwrapped with vapor-proof plasticfilm. If the poultry is in good initial condi-tion, additional shelf life may be obtained byvacuum packaging and gas flushing.


• Pallets—Most poultry is packed in fiber-board boxes and palletized for shipment.Ensure that the poultry is at the desired tran-sit temperature when loaded. Secure theboxes to the pallets with strapping or stretch

film to prevent them from top-

pling. Center-load the pallets off the walls(figure 12b).

Shell Eggs


• Desired transit temperature:40oF to 45oF (4o to 7oC)


• Average freezing point:28.0oF (–2oC)

Shell eggs are fragile and highly perishable.Even though it is not outwardly visible, eggquality deteriorates rapidly under poor envi-ronmental conditions.

Thoroughly clean and precool the truck ortrailer to at least 45oF (7oC) before eggs areloaded. Since eggs absorb odors, ensure thatthe vehicle is free of residual odors. Do notship eggs in mixed loads, especially not withcitrus fruits, onions, or potatoes.

Because of their perishability and the insu-lating effect of the fiberboard boxes and car-tons in which they are shipped, precool eggsto their desired transit temperature beforethey are loaded. Also, because the boxes arestacked tightly and may be secured on pal-lets with stretch film or strapping, there islittle or no cooling air circulating throughthe load. Pending Federal legislation willrequire that eggs destined for consumer mar-kets be precooled to at least 45oF (7oC)prior to loading and kept at or below thistemperature during transit.

Poultry and Eggs

68


• 30- and 15-dozen fiberboard boxes—Near-ly all eggs shipped in these boxes are pal-letized, 6 or 12 boxes per layer, on 48- x 40-inch pallets. However, to maximize use ofspace in the trailer, hand-stack one row ofboxes between the pallet rows in the middleof the trailer as in figure 20. Stack two rowsof boxes between the pallet rows in some102-inch (2.6 m) wide trailers.

Because eggs are so fragile, loading andbracing to prevent cargo movement isessential. To prevent forward shifting, loadthe first pallets snugly against the bulk-head, leaving no lengthwise slack betweenthe pallets until the end of the load. If thepallet load heights are uneven, use load-lock bars across the truck at the top layerto prevent forward or rearward shifting.Or, in some cases, tape the top one or two

layers of the pallet loads horizontally toprevent shifting.

Road shock and vibration are pronounced atthe rear of the truck. Therefore, take extracare to secure the load in this area. This maybe accomplished by shrink-wrapping thepallet loads at the rear doors (figure 20) andby using load-lock bars across the top of theload.

• Plastic crates—One-dozen cartons of eggsare shipped in plastic crates holding 15 or30 cartons. The cartons are retailed directlyfrom the crates. The crates fold or nest foreasy return to the egg packing plant.

• Roll-on/off carts—These carts hold 360 1-dozen cartons of eggs. They are positionedon the truck so that the cartons will not slideor shift off the carts. The carts are braced orsecured with load lock bars. The carts are

69

Figure 20. A palletized load ofeggs. Note the stretchfilm around the palletloads at the rear doorarea where road shockis greatest.

71

rolled off the truck and onto the retail floorwhere the eggs are sold off the cart. Emptycarts fold for less space on the return haul.Estimating Mobile Refrigeration RequirementsEstimate the number of Btu’s of heatloadwhen there is any question as to whether thetruck’s refrigeration system has adequatecapacity. This is particularly important inhot weather, if the pulp temperature of theproduct at loading is considerably above thedesired transit temperature. Shippers whooften receive claims of loss from decayshould make calculations to determine if therefrigeration capacity is adequate for eachload.

Consider the following three factors in esti-mating the heatload or amount of refrigera-tion needed to obtain and maintain the prop-er temperature during transit:

• Field or sensible heat (Hf) left in the com-modity and package

• Heat of respiration (Hr)

• Amount of heat leakage (Hl) through thewalls of the trailer

Add these three factors to get the total num-ber of Btu’s that must be absorbed by therefrigeration system.

Field heat (Hf) is the amount of heat that hasto be removed from the product and the con-tainers before the desired transit temperatureis reached. In practice, most products havenot been precooled to the desired transittemperature. This extra refrigeration require-ment must be allowed for. To calculate fieldheat load, use the specific heat (Sp.ht.) ofthe product (table I-1) and container, theweight (Wt.) of the product and container,and the temperature differential (TD) as

shown in the following formula:

Hf = SP.ht. x Wt. x TD = Btu

Determine heat of respiration (Hr) by usingthe information in table I-2, which gives theamount of heat generated by one ton of aproduct in 24 hours at different tempera-tures. To calculate the respiration heat, thefollowing formula can be used:

Hr = Respiration rate (at average transit tem-perature) x time (no. of days) x Wt. (tons)= Btu

Heat leakage (Hl) through the trailer body isestimated by determining:

• the coefficient of heat transfer (Ua factor)of the trailer body;

• the temperature differential between thethermostat setting and the average expect-ed outside temperature; and

• the number of hours the product will be inthe vehicle.

The Ua factor for a particular trailer bodydepends on many variables—type and thick-ness of insulation, air leakage, differentialbetween the outside and inside air tempera-tures, and others. Therefore, for the purpose ofestimating heat leakage it is impractical to givethe details of all calculations needed to deter-mine the Ua factor. However, the Ua factorbased on a standard method of rating can besupplied by the manufacturers of some trailers.If the Ua factor is not readily available, use thefollowing for general estimation of heatload:

• A factor Ua = 140 Btu/oF/hr. may be usedfor a modern 48-foot trailer with 2-1/2inches of plastic foam sidewall insulation.

• If the trailer has been in service over 3years, then a factor of 180 Btu/oF/hr.should be used to account for aging ofdeterioration of the insulation and door

Appendix I

72

Table I-1.—Specific Heat Above and Below Freezing of Certain PerishableProducts. (adapted with permission from ASHRAE Handbook—Refrigeration)

Fruits and Fruits andvegetables Btu/lb/oF. vegetables Btu/lb/oF.

Above Below Above Below

Apples . . . . . . . . . . . . . . . 0.87 0.45 Limes . . . . . . . . . . . . . . . . .89 .46Apricots . . . . . . . . . . . . . . .88 .46 Mangoes . . . . . . . . . . . . . . .85 .44Artichokes (globe) . . . . . . .87 .45 Mushrooms . . . . . . . . . . . 0.93 0.47Asparagus . . . . . . . . . . . . .94 .48 Nectarines . . . . . . . . . . . . .86 .44Avocados . . . . . . . . . . . . . .72 .40 Okra . . . . . . . . . . . . . . . . . .92 .46Bananas . . . . . . . . . . . . . . .80 .42 Onions (dry) . . . . . . . . . . . .90 .46Beans: Oranges . . . . . . . . . . . . . . .90 .46

Green snap . . . . . . . . . . .91 .47 Parsley . . . . . . . . . . . . . . . .88 .45Lima . . . . . . . . . . . . . . . .73 .40 Parsnips . . . . . . . . . . . . . . .84 .44

Beets (roots) . . . . . . . . . . . .90 .46 Peaches . . . . . . . . . . . . . . .91 .46Blackberries . . . . . . . . . . . .88 .46 Pears . . . . . . . . . . . . . . . . . .86 .45Blueberries . . . . . . . . . . . . .86 .45 Peas (green) . . . . . . . . . . . .79 .42Broccoli . . . . . . . . . . . . . . .92 .47 Peppers (sweet) . . . . . . . . .94 .47Brussels sprouts . . . . . . . . .88 .46 Pineapples . . . . . . . . . . . . .88 .45Cabbage . . . . . . . . . . . . . . .94 .47 Plums and freshCantaloupes . . . . . . . . . . . .93 .48 Prunes . . . . . . . . . . . . . . . .88 .45Carrots . . . . . . . . . . . . . . .. .90 .46 Potatoes:Casaba and Early-crop . . . . . . . . . . . .85 .44Crenshaw Late-crop . . . . . . . . . . . .82 .43

melons . . . . . . . . . . . . . .94 .48 Sweet (see Sweet potatoes)Cauliflower . . . . . . . . . . . .93 .47 Prunes (see Plums)Celery . . . . . . . . . . . . . . . . .95 .48 Pumpkins . . . . . . . . . . . . . .92 .47Cherries (sweet) . . . . . . . . .84 .44 Radishes . . . . . . . . . . . . . . .95 .48Corn (sweet) . . . . . . . . . . .79 .42 Raspberries:Cranberries . . . . . . . . . . . . .90 .46 Black . . . . . . . . . . . . . . . .84 .44Cucumbers . . . . . . . . . . . . .97 .49 Red . . . . . . . . . . . . . . . . .87 .45Eggplant . . . . . . . . . . . . . . .94 .48 Rhubarb . . . . . . . . . . . . . . .95 .48Endive and Escarole . . . . .94 .48 RomaineFigs (fresh) . . . . . . . . . . . . .82 .43 (see Lettuce)Garlic (dry) . . . . . . . . . . . .69 .40 Spinach . . . . . . . . . . . . . . .94 .48Gooseberries . . . . . . . . . . .90 .46 Squash:Grapefruit . . . . . . . . . . . . . .90 .46 Summer . . . . . . . . . . . . .95 .48Grapes . . . . . . . . . . . . . . . .86 .45 Winter . . . . . . . . . . . . . . .88 .45Honeydew melons . . . . . . .94 .48 Strawberries . . . . . . . . . . . .92 .47Kale . . . . . . . . . . . . . . . . . .89 .46 Sweet potatoes . . . . . . . . . .76 .41Leeks . . . . . . . . . . . . . . . . .88 .46 Tangerines . . . . . . . . . . . . .90 .46Lemons . . . . . . . . . . . . . . .91 .46 Tomatoes (ripe) . . . . . . . . .95 .48Lettuce (head) . . . . . . . . . .96 .48 Watermelons . . . . . . . . . . .97 .48

73

seals.

Hl = Ua x TD x time (hours) = Btu

Table I-1.—Specific Heat Above and Below Freezing of Certain PerishableProducts — Continued

Dairy, meat and Dairy, meat andpoultry products Btu/lb/oF. poultry products Btu/lb/oF.

Above Below Above Below

Bacon . . . . . . . . . . . . . . . . .38 .26 Lamb (fresh) . . . . . . . . . . .72 .40Beef (fresh) . . . . . . . . . . . .77 .41 Milk . . . . . . . . . . . . . . . . . .93 .46Butter . . . . . . . . . . . . . . . . .36 .25 Oleomargarine . . . . . . . . . .32 .25Cheese . . . . . . . . . . . . . . . .52 .31 Pork (fresh) . . . . . . . . . . . .53 .31Eggs (shell) . . . . . . . . . . . .73 .40 Poultry (fresh) . . . . . . . . . .80 .42Egg solids (whole) . . . . . . .22 .21 Smoked sausage . . . . . . . . .62 .35Egg yolk solids . . . . . . . . .23 .21 Veal (fresh) . . . . . . . . . . . .74 .40Ice cream . . . . . . . . . . . . . .70 .39Hams:

Cured . . . . . . . . . . . . . .. .67 .37Fresh . . . . . . . . . . . . . . .. .53 .31

74

Table I-2.—Approximate Amount of Respiration Heat Produced by CertainFruits and Vegetables at the Temperatures Indicated*

Commodity Btu per ton per 24 hours

32oF 40oF 60oF 70oF 80oF

Apples . . . . . . . . . . . . . 700 1,350 4,900 5,700 —Apricots . . . . . . . . . . . — 5,050 11,700 20,350 —Artichokes . . . . . . . . . 7,700 10,450 26,400 40,700 50,050Asparagus . . . . . . . . . . 9,700 18,050 38,500 48,750 93,250Avocados . . . . . . . . . . — 5,500 24,050 46,250 60,050 Bananas (green) . . . . . — — 4,850 7,400 —Beans:

Green snap . . . . . . . 7,250 10,300 38,100 49,200 —Lima (in pod) . . . . . 4,450 6,100 24,700 34,300 —

Beets . . . . . . . . . . . . . . 2,700 4,100 7,200 — —Blackberries . . . . . . . . 4,100 7,950 — 38,350 —Blueberries . . . . . . . . . 1,400 2,350 10,550 15,300 22,250Broccoli . . . . . . . . . . . 4,400 21,400 56,500 68,100 158,400Brussels sprouts . . . . . 4,400 7,700 22,000 28,350 —Cabbage . . . . . . . . . . 1,200 2,200 4,900 8,450 12,350Carrots . . . . . . . . . . . 3,300 4,300 8,750 15,500 —Cauliflower (trimmed) 3,900 4,500 10,100 17,700 24,650Celery . . . . . . . . . . . . 1,600 2,400 8,200 14,200 —Cherries:

Sour . . . . . . . . . . . . . 2,100 2,850 8,500 9,800 13,650Sweet . . . . . . . . . . . . 1,050 2,600 7,700 — —

Corn (sweet) . . . . . . . . 8,950 13,850 35,850 63,700 78,900Cranberries . . . . . . . . . 650 950 — 3,200 —Cucumbers . . . . . . . . . — — 5,300 6,850 8,050Endive and Escarole

(see Leaf lettuce)Figs (fresh) . . . . . . . . . — 2,650 12,350 16,700 21,000Gooseberries . . . . . . . . 1,700 2,850 5,950 — —Grapefruit . . . . . . . . . . — 1,000 3,100 4,250 —Grapes:

American . . . . . . . . . 600 1,200 3,500 7,200 8,500European . . . . . . . . . 400 1,000 2,400 — 6,050

Kale (whole leaves) . . 4,700 8,900 30,250 46,900 —Leeks . . . . . . . . . . . . . 2,900 5,350 21,950 — 24,850Lemons . . . . . . . . . . . . 700 1,250 3,650 4,850 5,350Lettuce:

Head . . . . . . . . . . . . 2,500 3,650 8,450 12,200 18,100Leaf . . . . . . . . . . . . 5,100 6,450 13,800 22,100 32,200

Limes . . . . . . . . . . . . . — 800 1,800 2,800 6,650Mangoes . . . . . . . . . . . — 3,500 9,900 24,900 26,400

75

Table I-2.—Approximate Amount of Respiration Heat Produced by CertainFruits and Vegetables at the Temperatures Indicated — Continued*



Melons:Cantaloupes . . . . . . . 1,200 2,050 7,950 12,000 14,700Honeydew . . . . . . . . — 900 3,050 5,150 6,700Watermelons . . . . . . — 800 — 4,650 —

Mushrooms . . . . . . . . . 7,900 15,600 46,000 63,800 —Nectarines (see

Peaches)Okra . . . . . . . . . . . . . . — 12,250 32,050 57,400 75,900Onions:

Dry . . . . . . . . . . . . . 650 750 2,400 3,650 6,200Green . . . . . . . . . . . . 3,600 9,400 17,950 25,800 33,800

Oranges . . . . . . . . . . . . 750 1,200 4,000 6,200 7,150Parsnips . . . . . . . . . . . 3,000 2,900 8,250 — —Peaches . . . . . . . . . . . . 1,150 1,700 8,300 17,750 22,350Pears:

Bartlett . . . . . . . . . . . 1,100 1,650 8,250 11,000 —Kieffer . . . . . . . . . . . 450 — 3,850 4,750 5,300

Peas:(green, in the pod) . . 8,500 14,450 41,900 66,750 79,200

Peppers (sweet) . . . . . — 2,900 8,500 9,650 12,100Pineapples . . . . . . . . . . — 400 3,450 7,050 10,800Plums (including

fresh Prunes) . . . . . 550 1,450 2,700 4,700 10,900Potatoes:

Uncured . . . . . . . . . . — 2,600 4,850 6,950 —Cured . . . . . . . . . . . — 1,250 1,950 2,650 —

Prunes (see Plums)Radishes (topped) . . . . 1,400 2,100 7,100 11,250 16,400Raspberries . . . . . . . . . 4,700 7,650 20,200 — —Rhubarb (without

leaves) . . . . . . . . . . . 2,350 3,200 8,700 10,650 —Romaine . . . . . . . . . . . — 4,550 9,750 15,100 23,850Spinach . . . . . . . . . . . . 4,550 10,150 39,350 50,550 —Squash:

Butternut . . . . . . . . . — — — — 20,650Yellow straight-

neck . . . . . . . . . . . 2,700 3,600 18,250 20,050 —Strawberries . . . . . . . . 3,300 5,450 17,950 32,800 41,800Sweet potatoes:

Cured . . . . . . . . . . . . — — 4,800 — —Uncured . . . . . . . . . . — — 6,300 — 14,000

76

Sample RefrigerationRequirement Calculation1

Assume that a trailer is loaded with plums in 30-pound fiberboard boxes:

Load = 1,200 boxes

Net wt. of fruit = 30 pounds per box

Total pounds = 36,000 pounds total (18 tons)

Net wt. of boxes = 2 pounds each

Total pounds = 2,400 pounds total

Sp. ht. of the fruit = 0.88 Btu/lb/oF (table I-1)

Sp. ht. box = 0.44 Btu/lb/oF2

1. Refrigeration needed to remove the remaining field heat in load:

Assumptions:Loading temperature = T1 = 52oFDesired transit temperature = T2 = 32oFTemperature differential = T1 – T2 = TD = 52o – 32o = 20o

then,Field heat (Hf) = WT. X Sp. ht. X TDHf product = 36,000 lb X 0.88 X 20o = 633,600 Btu

Hf boxes = 2,400 lb X 0.40 X 20o = 19,200 Btu

Total field heat = 633,600 + 19,200 = 652,800 Btu

Table I-2.—Approximate Amount of Respiration Heat Produced by CertainFruits and Vegetables at the Temperatures Indicated — Continued*



Tomatoes:Mature-green . . . . . . — 1,450 4,900 7,650 9,400Pink . . . . . . . . . . . . . — 1,300 5,850 7,500 9,050

Turnips . . . . . . . . . . . . 1,900 2,150 5,000 5,400 —Watercress . . . . . . . . . 5,050 10,150 40,700 — —

*Source: USDA Handbook No. 66, 1968

77

2. Transit refrigeration requirement for the heat of respiration:

Assumptions:If loading temperature = 52o and arrival temperature = 32oF.

then,

Average temperature of product during transit = 40oF.

Transit time = 3 days

then,

Heat of respiration (Hr) = Respiration rate at average transit temperature2

X time (days) X wt. (tons)

Hr = 1,450 X 3 X 18 = 78,300 Btu

3. Refrigeration needed for heat leakage through the trailer body:

Assumptions:A 48-foot trailer with a Ua factor = 140 Btu/oF/hr.

Average outside air temperature = T1 = 75oF

Thermostat setting = T2 = 34oF4

Temperature differential = TD = T1 - T2 = 75oF - 34oF = 41oF

thus,

Heat leakage (Hl) = Ua X TD (avg. outside air - thermostat setting) X time (hours) = Btu

Hl = 140 X 41 X 72 = 413,280 Btu

4. To get the total number of Btu’s the refrigeration must remove in 3 days:

Hf + Hr + Hl = 652,800 + 78,300 + 413,280 = 1,144,380 Btu

5. To determine the amount of refrigeration or refrigerant needed:

Mechanical capacity needed = 1,144,380 Btu / 72 hrs. = 15,894 Btu hr.

Ice = total pounds needed for 3-day trip = 1,144,380 Btu / 1445 = 7,947 lb

Liquid nitrogen (N2) = total pounds needed for 3-day trip = 1,144,380 Btu / 1756 = 6,539 lb

1 This calculation does not take into account the following factors: (1) the amount of refrigeration needed to precoolthe vehicle body; (2) air inside the vehicle; and (3) refrigeration needed to counteract air leakage around doors andother places in the body.

2 This figure approximates the specific heat of most wood and fiberboard containers.3 See table I-2, plums at 40oF4 For products with a desired transport temperature near 32oF, the thermostat should be set several degrees higher to

decrease the chance of freezing damage.5 One pound of ice will absorb 144 Btu’s of heat.6 One pound of liquid nitrogen will absorb approximately 175 Btu’s of heat at temperatures above 32oF.

78

Appendix II

Load Compatibility Groups1

Group 1

• Apples• Apricots• Berries (except cranberries)• Cherries• Figs (not with apples, danger of odor transfer to figs; also see group 6a)• Grapes2 (see groups 2 and 6a)• Peaches• Pears• Persimmons• Plums and prunes• Pomegranates• Quinces

Recommended Transit Conditions:

• Temperature:32o to 34oF (0o to 1.5oC)

• Relative humidity:90 to 95 percent

• Atmosphere:Normally used on berries and cherries only—10 to 20 percent CO2

• Ice:Never in contact with commodity.

Note: Most members of this group are not compatible with group 6a or 6b because ethyleneproduction by group 1 can be high, and thus harmful to members of group 6a or 6b.

1 Taken from USDA Marketing Research Report No. 1070, “Compatibility of Fruits and Vegetables During Transportin Mixed Loads,” by W. J. Lipton and J. M. Harvey, 1977.

2 Grapes: Compatible with other commodities only if the grapes are not fumigated with sulfur dioxide (SO2) in vehicleand if no chemicals that release SO2 are included in packages.

Group 2

• Avocados• Bananas

79

• Eggplants (also see group 5)• Grapefruit3

• Guava• Limes• Mangoes• Muskmelons, other than cantaloupes

CasabaCrenshawHoney DewPersian

• Olives, fresh• Papayas• Pineapples (not with avocados, danger of avocados’ odor absorption)• Tomatoes, green• Tomatoes, pink (also see group 4)• Watermelons (also see groups 4 and 5)


• Temperature:55o to 65oF (13o to 18oC)


• Ice:Never in contact with commodity

3 Citrus Fruits : Oranges and tangerines—compatibility depends on source. Florida- or Texas-grown oranges areshipped at 32o to 34oF (0.0o to 1.1oC), but oranges grown in California and Arizona are shipped at 38o to 48oF (3.3o

to 8.8o C).

Group 3

• Cantaloupes• Cranberries• Lemons (adjust temperature to other commodity)• Lychees (also see group 4)• Oranges• Tangerines


• Temperature:36o to 41oF (2.5o to 5.0oC)

• Relative humidity:90 to 95 percent; cantaloupes about 95 percent

• Ice:In contact only with cantaloupes

80

Group 4

• Beans, snap• Lychees (also see group 3)• Okra• Peppers, green (not with beans)• Peppers, red (if with green peppers, temperature adjusted toward top of range)• Squash, summer• Tomatoes, pink (also see group 2)• Watermelons (also see groups 2 and 5)


• Temperature:40o to 45oF (4.5o to 7.5oC)

• Relative humidity:About 95 percent


Group 5

• Cucumbers• Eggplants (also see group 2)• Ginger (not with eggplants, also see group 7)• Grapefruit, Florida (after January 1), and Texas• Potatoes (late crop)• Pumpkin and squashes, winter• Watermelons (temperature adjusted for other members of groups; also see groups 2 and 4)


• Temperature:40o to 55oF (4.4o to 13oC); ginger not below 55oF



81

Group 6a

• Artichokes• Asparagus• Beets, red• Carrots• Endive and escarole• Figs (also see group 1)• Grapes (also see group 1)• Greens• Leeks (not with figs or grapes)• Lettuce• Mushrooms• Parsley • Parsnips• Peas• Rhubarb• Salsify • Spinach• Sweet corn• Watercress

This group, except for figs, grapes, and mushrooms, is compatible with group 6b.




• Ice:Never in contact with asparagus, figs, grapes, or mushrooms

Group 6b

• Broccoli• Brussels sprouts• Cabbage• Cauliflower• Celeriac• Horseradish• Kohlrabi• Onions, green (not with rhubarb, figs, grapes, mushrooms, or sweet corn)• Radishes• Rutabagas• Turnips

This group is compatible with group 6a, except for figs, grapes, and mushrooms.

82




• Ice:Contact acceptable for all

Group 7

• Ginger (also see group 5)• Potatoes, early crop (temperatures adjusted for others)• Sweet potatoes


• Temperature:55o to 65oF (13o to 18oC)



Group 8

• Garlic• Onions, dry





83

Appendix III

Table III-1.—Recommended Protective Services for Perishable Foods DuringTransit

Top-iceRecommended Desired Highest and/or1

Transit Relative Freezing Package-iceProduct Temperature Humidity Point OK

oF oC Percent oF oCFresh fruits and

vegetables:

Apples . . . . . . . . . . . 30 - 40 –1.1 - 4.4 90 - 95 30.0 –1.1 No(depending onvariety)Apricots . . . . . . . . . . 32 0.0 90 - 95 30.1 –1.1 NoArtichokes (globe) . . 32 0.0 95 - 100 29.9 –1.2 YesAsparagus . . . . . . . . 32 - 35 0.0 - 1.7 95 - 100 30.9 –0.6 NoAvocados:

Cold-tolerantvarieties . . . . . . . . 40 4.4 85 - 90 31.5 –0.3 NoCold-intolerantvarieties . . . . . . . . 55 12.8 85 - 90 31.5 –0.3 No

Bananas . . . . . . . . . . 56 - 58 13.3 - 14.4 90 - 95 30.6 –0.8 NoBeans:

Green or snap . . . . 40 - 45 4.4 - 7.2 95 30.7 –0.7 NoLima, in pods . . . . 37 - 41 2.8 - 5.0 95 31.0 –0.6 No

Beets . . . . . . . . . . . . 32 0.0 98 - 100 30.3 –0.9 YesBeet tops . . . . . . . . . 32 0.0 95 - 100 31.3 –0.4 YesBlackberries . . . . . . . 31 - 32 –0.6 - 0.0 90 - 95 30.5 –0.8 NoBlueberries . . . . . . . . 31 - 32 –0.6 - 0.0 90 - 95 29.7 –1.3 NoBroccoli . . . . . . . . . . 32 0.0 95 - 100 30.9 –0.6 YesCabbage . . . . . . . . . . 32 0.0 98 - 100 30.4 –0.9 YesCantaloupes . . . . . . . 36 - 41 2.2 - 5.0 95 29.9 –1.2 Yes Carrots . . . . . . . . . . . 32 0.0 98 - 100 29.5 –1.4 YesCauliflower . . . . . . . 32 0.0 90 - 98 30.6 –0.8 YesCelery . . . . . . . . . . . . 32 0.0 98 - 100 31.1 –0.5 YesCherries:

Sweet . . . . . . . . . . 30 - 31 –1.1 - –0.6 90 - 95 28.8 –1.8 NoSour . . . . . . . . . . . 32 0.0 90 - 95 29.0 –1.7 No

Corn (sweet) . . . . . . 32 0.0 95 - 98 30.9 –0.6 YesCranberries . . . . . . . . 36 - 40 2.2 - 4.4 90 - 95 30.4 –0.9 NoCucumbers . . . . . . . . 50 - 55 10.0 - 12.8 95 31.1 –0.5 NoEggplants . . . . . . . . . 46 - 54 8.0 - 12.2 90 - 95 30.6 –0.8 No

84

Table III-1.—Recommended Protective Services for Perishable Foods DuringTransit — Continued




vegetables: — Continued

Endive (escarole) . . . 32 0.0 90 - 95 31.9 –0.1 YesGarlic (dry) . . . . . . . 32 - 34 0.0 - 1.1 65 - 75 30.5 –0.8 NoGrapefruit:

Arizona andCalifornia . . . . . . . 58 - 60 14.0 - 15.6 85 - 90 30.0 –1.1 NoFlorida and Texas . 50 - 60 10.0 - 15.6 85 - 90 30.0 –1.1 No

Grapes:American type . . . 32 0.0 85 29.7 –1.3 NoEuropean type

(Vinifera) . . . . . . 30 - 31 –1.1 - –0.6 90 - 95 28.1 –2.2 NoKale . . . . . . . . . . . . . 32 0.0 95 - 100 31.1 –0.5 YesKiwi Fruit . . . . . . . . 32 0.0 90 - 95 29.0 –1.7 NoLemons . . . . . . . . . . 45 - 55 7.2 - 12.8 85 - 90 29.4 –1.4 NoLettuce . . . . . . . . . . . 32 0.0 98 - 100 31.7 –0.2 NoLimes . . . . . . . . . . . . 48 - 50 8.9 - 10.0 85 - 90 29.1 –1.6 NoMangoes . . . . . . . . . . 55 12.8 85 - 90 30.3 –0.9 NoMelons:

Honeydew, Casaba,Crenshaw, andPersian . . . . . . . . . 45 - 50 7.2 - 10.0 90 - 95 30.5 –0.8 No

Mushrooms . . . . . . . 32 0.0 95 30.4 –0.9 NoOkra . . . . . . . . . . . . . 45 - 50 7.2 - 10.0 90 - 95 28.7 –1.8 NoOnions (dry) . . . . . . . 32 0.0 65 - 70 30.6 –0.8 NoOnions (green) . . . . . 32 0.0 95 - 100 30.4 –0.9 YesShallots . . . . . . . . . . 32 0.0 95 - 100 31.6 –0.2 YesLeeks. . . . . . . . . . . . . 32 0.0 95 - 100 30.7 –0.7 YesOranges2 . . . . . . . . . 32 - 48 0.0 - 8.8 85 - 90 30.6 –0.8 No . . . . . . . . . . . . . . . . . (flesh) . . . . . . . . . . . . . . . . . 29.7 –1.3 . . . . . . . . . . . . . . . . . (peel)Parsley . . . . . . . . . . . 32 0.0 95 - 100 30.0 –1.1 YesParsnips . . . . . . . . . . 32 0.0 98 - 100 30.4 –0.9 YesPeaches and

Nectarines . . . . . . . 31 - 32 –0.6 - 0.0 90 - 95 30.4 –0.9 NoPears3 . . . . . . . . . . . . 32 0.0 90 - 95 29.2 –1.6 No

85






Peas:(green, in pods) . . 32 0.0 95 - 98 30.9 –0.6 Yes

. . . . . . . . . . . . . . . . . (pods) . . . . . . . . . . . . . . . . . 29.9 –1.2 . . . . . . . . . . . . . . . . . (shelled)Peppers (sweet) . . . . 45 - 55 7.2 - 12.8 90 - 95 30.7 –0.7 NoPineapples:

Mature-green . . . . 50 - 55 10.0 - 13.0 85 - 90 30.0 –1.1 No Ripe Fruit . . . . . . . . . 45 7.2 85 - 90 30.0 –1.1 NoPlums and Fresh

Prunes . . . . . . . . . . 32 0.0 90 - 95 30.5 –0.8 NoPotatoes:

Early crop fortable . . . . . . . . . . 50 - 60 10.0 - 15.6 90 30.9 –0.6 No

Early crop forchipping . . . . . . . 65 - 70 18.3 - 21.1 90 30.9 –0.6 No

Late crop fortable . . . . . . . . . . 40 - 50 4.4 - 10.0 90 30.9 –0.6 No

Late crop forchipping . . . . . . . 50 - 60 10.0 - 15.6 90 30.9 –0.6 No

Radishes . . . . . . . . . . 32 0.0 95 - 100 30.7 –0.7 YesRaspberries . . . . . . . 32 0.0 90 - 95 30.0 –1.1 No . . . . . . . . . . . . . . . . . (black) . . . . . . . . . . . . . . . . . 30.9 –0.6 . . . . . . . . . . . . . . . . . (red)Rhubarb . . . . . . . . . . 32 0.0 95 - 100 30.3 –0.9 NoRomaine . . . . . . . . . . 32 0.0 95 31.7 –0.2 YesSalad mixes . . . . . . . 33 0.6 90 - 95 (varies) NoSpinach . . . . . . . . . . 32 0.0 95 - 100 31.5 –0.3 YesSquash and

Pumpkins:Winter . . . . . . . . 50 - 55 10.0 - 12.8 50 - 70 30.5 –0.8 NoSummer . . . . . . . 41 - 50 5.0 - 10.0 95 31.1 –0.5 No

Strawberries . . . . . . . 32 0.0 90 - 95 30.6 –0.8 NoSweet potatoes . . . . . 55 - 60 12.8 - 15.6 85 - 90 29.7 –1.3 NoTangerines . . . . . . . . 40 4.4 90 - 95 30.1 –1.1 No

86






Tomatoes:Mature-green . . . . 55 - 70 12.8 - 21.1 90 - 95 31.0 –0.6 NoPink . . . . . . . . . . . . 46 - 50 7.2 - 10.0 90 - 95 31.1 –0.5 No

Watermelons . . . . . . 50 - 60 10.0 - 15.6 90 31.3 –0.4 NoCanned Foods4 . . . . — — — — — —

Dairy Products:

Butter:Fresh . . . . . . . . . 39 3.9 75 - 85 NoFrozen . . . . . . . . –10 –23.3 No

Margarine . . . . . . . 35 1.7 60 - 70 NoMilk (whole) . . . . . 32 - 34 0.0 - 1.1 ———— 31.0 –0.6 No Cheese5 . . . . . . . . . 34 - 40 1.0 - 4.0 65 - 70 NoIce Cream . . . . . . . –20 - –15 –29 - –26 ———— 21.0 –6.0 No

Fresh and Cured Meat and Seafood6 . . . . . . . . — — — — — —

Frozen Foods7 . . . . . — — — — — —

Poultry and Eggs:

Fresh . . . . . . . . . . . 26 - 34 -3.0 - 1.1 90 - 95 27.0 –2.8 YesHard, chilled . . . . . 0 - 26 –18 - –3 90 - 95 27.0 –2.8 NoEggs . . . . . . . . . . . 40 - 45 4.4 - 7.2 80 - 85 28.0 –2.2 No

1 Make sure products are packed in moisture resistant containers before applying top- or package-ice.2 Florida and Texas oranges shipped from cold storage or those that will be in transit for more than 5 days should be

held at 32–34oF (0.0o to 1.1oC). Arizona and California oranges should be shipped at 38o to 48oF.3 Early Bartlett pears that are ripened in transit should be shipped at 55–60oF.4 See text page 57 and table 4.5 See text page 60 and table 5.6 See text page 62 and table 6.7 All frozen foods should be shipped at 0oF (–18oC) or below.

Selected Bibliography

American Society of Heating, Refrigerating, and Air-Conditioning Engineers, ASHRAEHandbook—Refrigeration Systems and Applications, Atlanta, GA, various editions.

Ashby, et al., User’s Guide to the RTF Truck Trailer Classification, Transportation Tips No.8, AMS-TMD, U.S. Department of Agriculture, Washington, DC, March 1989.

Frozen Food Roundtable, Frozen Food Handling and Merchandising—A Code of Recom-mended Practices, Washington, DC, 1992.

Hardenburg, R.E., et al. The Commercial Storage of Fruits, Vegetables, and Florist andNursery Stocks, Agricultural Handbook No. 66, ARS, U.S. Department of Agriculture,Washington, DC, 1986.

Kasmire, R.F. and R. Tom Hinsch, Maintaining Optimum Transit Temperatures in Refriger-ated Truck Shipments, University of California Perishables Handling Supplement No. 2,University of California, Davis, CA 95616, and ARS, U.S. Department of Agriculture, Fres-no, CA, April 1987.

Lipton, W.J. and John M. Harvey, Compatibility of Fruits and Vegetables During Transportin Mixed Loads, MRR-1070, ARS, U.S. Department of Agriculture, Washington DC, May1977.

McGregor, Brian M., Tropical Products Transport Handbook, Agricultural Handbook No.668, U.S. Department of Agriculture, Washington, DC, 1987.

Nicholas, C.J., Export Handbook for U.S. Agriculture Products, Agricultural Handbook No.593, U.S. Department of Agriculture, Washington, DC, March 1985.

The Packer, Produce Availability & Merchandising Guide, Vance Publishing Corp., Over-land Park, KS, 1993.

The Refrigeration Research Foundation, Commodity Storage Manual,International Association of Refrigerated Warehouses, Bethesda, MD.

Transfresh, Fresh Produce Mixer & Loading Guide, Transfresh Corp., Salinas, CA, 1988.

Contact the Refrigerated Transportation Library, Department of Pomology, Wickson Hall,University of California, Davis, CA 95616, for a catalog of videos, slide sets, and printedmaterial that may be either purchased or obtained free. The items in the catalog are of inter-est to those involved in the transportation of perishable foods. It comprises the library of theRefrigerated Transportation Foundation and other resources available from the University ofCalifornia, Davis, Cooperative Extension and the U.S. Department of Agriculture. Preferred CitationAshby, B. Hunt. Protecting Perishable Foods During Transport by Truck. U.S. Department of Agriculture, Agricultural Marketing Service, September 1995, reprinted July 2006. Web. <http://dx.doi.org/10.9752/TS024.07-2006>

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