The Commercial Storage of Fruits, Vegetables, Florist and Nursery Stocks

8/16/2019 The Commercial Storage of Fruits, Vegetables, Florist and Nursery Stocks

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United States Department of Agriculture

AgriculturalResearchService

Agriculture HandbookNumber 66

Revised February 2016

The Commercial Storageof Fruits, Vegetables, and

Florist and Nursery Stocks


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AgriculturalResearchService

Agriculture HandbookNumber 66

The Commercial Storageof Fruits, Vegetables, and

Florist and Nursery StocksEdited by Kenneth C. Gross, Chien Yi Wang, and Mikal Saltveit

_______________________________________________________________ Gross and Wang are formerly with the Food Quality Laboratory, BeltsvilleAgricultural Research Center, USDA, Agricultural Research Service,Beltsville, MD. They are now retired. Saltveit is with the Department ofPlant Sciences, University of California, Davis, CA.

United States Department of Agriculture


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Abstract

Gross, Kenneth C., Chien Yi Wang, and MikalSaltveit, eds. 2016. The Commercial Storage ofFruits, Vegetables, and Florist and Nursery Stocks.Agriculture Handbook 66, U.S. Departmentof Agriculture, Agricultural Research Service,

Washington, DC.

Agriculture Handbook 66 (AH-66) representsa complete revision and major expansion ofthe 1986 edition. It has been reorganized andnow includes 17 Chapters and 138 CommoditySummaries written by nearly a hundred expertsin plant science and postharvest technology.This version, like the previous editions of AH-66 in 1954, 1968, 1977, and 1986, presentssummaries of current storage requirements

of fresh fruits, vegetables, cut owers, andother horticultural crops. However, this highlyexpanded version also includes information onquality characteristics, maturity indices, grading, packaging, precooling, retail display, chillingsensitivity, ethylene production and sensitivity,respiration rates, physiological disorders, postharvest pathology, quarantine issues, andsuitability as fresh-cut product. A large numberof fruits and vegetables were added, as wellas sections on food safety, nutritional quality,

texture, and fresh-cut produce. The purpose ofstoring plant material is to lengthen the time itcan be consumed or utilized. In doing so, it iscritical to provide an environment that minimizesdeterioration, maintains microbial safety, andretains other quality attributes. AH-66 providesguidelines and other important information forstoring and handling horticultural commoditiesto accomplish this.

Keywords: carbon dioxide, chilling injury,cold storage, controlled atmosphere storage,cut owers, ethylene, avor, food safety,

fresh-cut, fresh produce, fruit softening, heatload, 1-methylcyclopropene, microbial safety,minimally processed, modied-atmosphere

packaging, potted plants, nutritional quality, nuts,orchids, packaging lm, perishable, postharvest

biology, precooling, respiration, sensoryevaluation, shelf-life, texture.

The information contained in AH-66 has beenassembled from material prepared by nearly ahundred authors from around the world. All of theinformation contained herein was peer reviewedand edited for scientic content. Every effort was

made to provide the most accurate and currentinformation available.

The contributors’ professional afliations

and addresses were up-to-date at the time ofsubmission of their chapters, and the editorsmade all reasonable efforts to update any changesreceived during the review and publishing process.However, due to the large number of contributorsand countries represented, it is not inconceivablethat some of the contributors may have changedorganizations in the interim and thus are nolonger at the addresses given in this handbook. In

cases where the editors received specic addresschanges or death notices, all such updates arereected in this volume.

Mention of trade names or commercial productsin this report is solely for the purpose of pro-viding specic information and does not imply

recommendation or endorsement by the U.S.Department of Agriculture.

This publication reports experimental results

and other information involving pesticides. Itdoes not contain recommendations for their usenor does it imply that uses discussed here have been registered. All uses of pesticides must beregistered by appropriate State and/or Federalagencies before they can be recommended.

While supplies last, printed copies of this publication may be obtained at no cost from theUSDA-ARS Food Quality Laboratory, Building002, Room 117, 10300 Baltimore Avenue,

Beltsville, MD 20705-2350.

Copies of this publication may be purchasedin various formats (microche, photocopy,

CD, and print on demand) from the NationalTechnical Information Service, 5285 Port RoyalRoad, Springeld, VA 22161, (800) 553-6847,

http//:www.ntis.gov.


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This publication in its entirety is freely accessibleon the Internet at http://www.ars.usda.gov/is/np/indexpubs.

ARS Mission

The Agricultural Research Service conducts

research to develop and transfer solutions toagricultural problems of high national priorityand provides information access and dissemi-nation to—ensure high-quality, safe food and otheragricultural products; assess the nutritional needsof Americans; sustain a competitive agriculturaleconomy; enhance the natural resource baseand the environment; and provide economicopportunities for rural citizens, communities, andsociety as a whole.

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs andactivities on the basis of race, color, nationalorigin, age, disability, and where applicable, sex,marital status, familial status, parental status,religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or partof an individual’s income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons withdisabilities who require alternative means for

communication of program information (Braille,large print, audiotape, etc.) should contact USDA’sTARGET Center at (202) 720-2600 (voice andTDD). To le a complaint of discrimination,

write to USDA, Director, Ofce of Civil Rights,

1400 Independence Avenue, S.W., Washington,D.C. 20250-9410, or call (800) 795-3272 (voice)or (202) 720-6382 (TDD). USDA is an equalopportunity provider and employer.

Revised February 2016


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Acknowledgments

The editors gratefully acknowledge the generousassistance and helpful contributions of thefollowing reviewers: Douglas Adams, Leo GeneAlbrigo, Douglas Archbold, Reginaldo Baez-Sanudo, Elizabeth Baldwin, Randolph Beaudry,

John Beaulieu, Shimshon Ben-Yehoshua, PaulBlankenship, Sylvia Blankenship, WilliamBramlage, Jeffery Brecht, Kathleen Brown,Jem Burdon, Arthur Cameron, Marita Cantwell,William Conway, Stephen Drake, Bob Elliott,Timothy Facteau, Ian Ferguson, Louise Ferguson,Charles Forney, Maria Gil-Munoz, GustavoGonzalez-Aguilar, Jim Gorny, Robert Griesbach,Laurie Houck, Don Huber, Benjamin Juven, AdelKader, Angelos Kanellis, Stan Kays, DangyangKe, Walter Kender, Saichol Ketsa, Lisa Kitinoja,

Wei Chin Lin, Werner Lipton, Bruce Lish, KeithStanley Mayberry, Don Maynard, ElizabethMitcham, Yosef Mizrahi, Robert John Mullen,Timothy Ng, Chuck Orman, Robert Paull,Penelope Perkins-Veazie, David Picha, RobertPrange, William Proebsting, Stanley Prussia,Michael Reid, Mark Ritenour, Mark Roh, BillRomig, Vincent Rubatzky, Carl Sams, StevenSargent, Philip Shaw, Krista Shellie, RichardSnyder, Meisheng Tian, Peter Toivonen, RonaldVoss, Yin-Tung Wang, Bruce Whitaker, George

Wilson, Allan Woolf, Elhadi Yahia, Charles Yang,Devon Zagory, and Francis Zee.


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Abbreviations

APHIS Animal and Plant Health InspectionService, USDA

ARS Agricultural Research Service, USDABTU British thermal unit bu bushel

CaCl2 calcium chlorideCDC Centers for Disease Control

and PreventionCO

2carbon dioxide

cm centimeter cfu colony forming unitsCA controlled atmosphereCFM cubic feet per minuteed., eds. editor; editorsEPA Environmental Protection AgencyFDA Food and Drug Administration, HHS

ft feetGC gas chromatographGRAS generally recognized as safeh hour HAT high temperature forced-air treatmentHg mercuryHHS United States Department of Health

and Human ServicesHWB hot water brushing HWT hot water treatmentin inch

J Jouleskg kilogramL liter MS mass spectrometer m meter mL milliliter MA modied atmosphere

MAP modied atmosphere packaging

µL microlitermin minutemo month

N Newtons N

2nitrogen

nL nanoliter oz ounce, AvoirdupoisO

2oxygen

OTR oxygen transmission rate ppb parts per billion ppm parts per million% percent

lb pound, avoirdupoisRH relative humiditysec second T short tonSTS silver thiosulfate NaOCl sodium hypochloriteSSC soluble solids content

SO2 sulfur dioxideTA total aciditySSC total soluble solidsU.S. United StatesUSDA United States Department

of AgricultureVHT vapor heat treatment


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Contents

Introduction ...........................................................1Temperature Conversion Chart .............................2Metric Conversion Chart.......................................3Commodity Cross-Reference ................................4Respiration and Ethylene Production Rates ..........7

Postharvest Biology and TechnologyPrecooling and Storage Facilities........................11Heat Load Calculation ........................................19Controlled Atmosphere Storage ..........................22Temperature Preconditioning ..............................26Modied Atmosphere Packaging ........................42Wholesale Distribution Center Storage ..............54Grocery Store Display Storage ...........................59Chilling and Freezing Injury ...............................62Respiratory Metabolism ......................................68

Ethylene Effects ..................................................761-Methylcyclopropane (MCP) ............................83Texture ................................................................89Postharvest Pathology ....................................... 111Flavor ................................................................128Food Safety .......................................................149 Nutritional Quality and Its

Importance in Human Health ........................166

Commodity Summaries-----Fruits and Vegetables-----

Annual Culinary Herbs .....................................173Apple .................................................................176Apricot ..............................................................195Arazá .................................................................198Artichoke ...........................................................202Asian Pear .........................................................205Asparagus ..........................................................210Atemoya ............................................................214Avocado ............................................................216Banana and Plantain ..........................................224Bean ..................................................................230

Beet ...................................................................234Blackberry .........................................................237Blueberry...........................................................240Bok Choy ..........................................................243Breadfruit ..........................................................245Broccoli .............................................................248Brussels Sprouts ................................................252Cabbage.............................................................255Carambola .........................................................261

Carrot ................................................................264Cassava .............................................................268Cauliower ........................................................271Celeriac .............................................................275Celery ................................................................277Cherimoya .........................................................280Cherry (Sweet) ..................................................282

Chicory (Belgian Endive or Witloof Chicory) ..286Chinese Cabbage ...............................................289Coconut .............................................................294Cranberry ..........................................................297Cucumber ..........................................................302Currant, Gooseberry, and Elderberry ................306Date ...................................................................311Dragon Fruit ......................................................315Durian ...............................................................318Eggplant ............................................................322Endive and Escarole ..........................................326

Fennel ................................................................328Fig .....................................................................330Garlic.................................................................333Ginger ...............................................................336Ginseng .............................................................338Grape (American) .............................................340Grape (Muscadine)............................................342Grape (Table) ....................................................344Grapefruit ..........................................................349Greens for Cooking ...........................................353Guava ................................................................356

Honeydew Melon ..............................................358Horseradish .......................................................362Jerusalem Artichoke ..........................................365Jicama ...............................................................369Kiwifruit ............................................................372Kohlrabi ............................................................377Leek...................................................................379Lemon ...............................................................382Lettuce...............................................................386Lime ..................................................................390Litchi .................................................................392

Longan ..............................................................395Longkong ..........................................................398Loquat ...............................................................401Luffa ..................................................................403Mandarin (Tangerine) .......................................405Mango ...............................................................408Mangosteen .......................................................412Mushroom .........................................................415 Nectarine ...........................................................418


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Netted Melon ....................................................423 Nopalitos ...........................................................427Okra...................................................................430Olive ..................................................................433Onion.................................................................436Orange ...............................................................441Papaya ...............................................................447

Parsley ...............................................................453Parsnip...............................................................457Passion Fruit......................................................460Pea .....................................................................463Peach .................................................................466Pear ...................................................................471Pepper ...............................................................481Perennial Culinary Herbs .................................. 485Persimmon ........................................................487Pineapple ...........................................................491Plum and Fresh Prune ....................................... 497

Pomegranate ...................................................... 501Potato ................................................................506Prickly Pear ....................................................... 511Pumpkin and Winter Squash ............................. 514Quince ...............................................................518Radicchio ..........................................................521Radish ...............................................................524Rambutan ..........................................................527Raspberry ..........................................................530Rhubarb .............................................................533Rutabaga ...........................................................535

Salad Greens .....................................................538Salsify ...............................................................541Sapodilla and Related Fruit ............................... 543 Black Sapote ............................................... 543 Lucuma .......................................................543 Mamey Apple .............................................. 544 Sapodilla ..................................................... 544 Sapote ..........................................................546 Star Apple....................................................546 White Sapote ............................................... 547Southern Pea .....................................................550

Sprouts ..............................................................553Squash ...............................................................556Strawberry .........................................................560Sweet Corn ........................................................562Sweetpotato .......................................................566Swiss Chard ......................................................571Tamarillo ...........................................................573Tamarind ...........................................................575Taro ...................................................................577

Tomatillo ...........................................................579Tomato ..............................................................581Trufe ................................................................588Turnip ................................................................590Waterchestnut ....................................................592Water Convolvulus ............................................ 595Watercress .........................................................597

Watermelon .......................................................599Wax Apple .........................................................602

-----Fresh-Cut Produce-----Fresh-Cut Fruits ................................................604Fresh-Cut Vegetables ........................................624

-----Floral Crops and Nursery Stock-----Bedding Plants and Seedlings ...........................642Christmas Trees ................................................. 650Cut Flowers and Greens .................................... 659

Flower Bulbs .....................................................709Flowering Potted Plants .................................... 722Foliage Plants ....................................................725Herbaceous Perennials ...................................... 727Orchids ..............................................................732Seeds and Pollen ...............................................735

-----------Nuts-----------Almond .............................................................744Hazelnut ............................................................748Macadamia Nut ................................................. 754

Peanut ................................................................757Pecan .................................................................768Pistachio ............................................................772Walnut ...............................................................777


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Temperature Conversion Chart

°C = 5/9 (°F - 32)°F = (9/5 × °C) + 32

°C °F °C °F-2 28.4 23 73.4

-1 30.2 24 75.2 0 32.0 25 77.0 1 33.8 26 78.8 2 35.6 27 80.6 3 37.4 28 82.4 4 39.2 29 84.2 5 41.0 30 86.0 6 42.8 31 87.8 7 44.6 32 89.6 8 46.4 33 91.4 9 48.2 34 93.2

10 50.0 35 95.0 11 51.8 36 96.8 12 53.6 37 98.6 13 55.4 38 100.4 14 57.2 39 102.2 15 59.0 40 104.4 16 60.8 45 113.0 17 62.6 50 122.0 18 64.4 55 131.0 19 66.2 60 140.0 20 68.0 65 149.0

21 69.8 70 158.0 22 71.6 75 167.0


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Metric Conversion Chart

Mass1.0 avoirdupois pound (lb) = 0.454 kilogram (kg) = 454 grams (g)1.0 kilogram (kg) = 2.2 pounds (lb) = 35.2 avoirdupois ounces (oz) = 32.15 troy ounces1.0 avoirdupois ounce (oz) = 0.9115 troy ounce = 0.0284 kilogram (kg) = 28.4 grams (g)1 short ton (T) = 2,000 pounds (lb) = 907.2 kilograms (kg) = 0.893 long ton = 0.907 metric tonne

Length1 inch (in) = 2.54 centimeters (cm)1 centimeter (cm) = 0.394 inch (in)1 foot (ft) = 30.48 centimeters (cm)1 yard (yd) = 91.44 centimeters (cm) or 0.9144 meter (m)1 meter (m) = 3.28 feet (ft) = 1.0936 yards (yd)1 mile (mi) = 1.61 kilometers (km)1 kilometer (km) = 0.621 mile (mi)

Volume

1 quart (qt) = 0.946 liter (L)1 liter (L) = 1.057 quarts (qt)1 cup (c) = 0.24 liter (L)1 pint (pt) = 0.47 liter (L)1 quart (qt) = 0.95 liter (L)1 U.S. bushel (bu) = 35.24 liters (L)1 liter (L) = 0.2838 bushel (bu)1 U.S. gallon (gal) = 3.785 liters (L)1 liter (L) = 0.2642 gallon (gal)1 cubic foot (ft3) = 28.32 liters (L)1 cubic yard (yd 3) = 0.76 cubic meter (m3)

1 liter (L) = 61.02 cubic inches (in3)

Area1 acre = 0.4047 hectare1 hectare = 2.47 acres1 square meter (m2) = 1550 square inches (in2) = 1.196 square yards (yd 2) = 10.76 square feet (ft2)1 square inch (in2) = 6.45 square centimeters (cm2)1 square foot (ft2) = 0.0929 square meter (m2)

Energy/Work 1 joule (J) = 0.00094 British thermal units (BTU) = 1 watt per second (W s-1)

1 British thermal unit (BTU) = 1,055 joules (J) = 0.252 kilocalorie (kcal)


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Commodity Cross-Reference

To nd... See...

Abogado AvocadoAlligator pear AvocadoAlfalfa sprouts SproutsAnon Sapodilla

Apple cactus Dragon fruitApple pear (misleading) Asian pear Araçá boi ArazáAvocat AvocadoBasil Annual culinary herbsBean sprouts SproutsBeets BeetBelgian endive ChicoryBell pepper Pepper Bhendi OkraBhindi Okra

Boy-toyo Bok choyCactus fruit Prickly pear Cactus pad NopalitosCactus pear Prickly pear Caimito SapodillaCalabaza PumpkinCalabrese BroccoliCanary melon Honeydew melonCantelope Netted melonCasaba melon Honeydew melonCassave Cassava

Cay mang cut MangosteenChervil Annual culinary herbsChico mamey SapodillaChico zapote SapodillaChiku SapodillaChile pepper Pepper Chinese apple PomegranateChinese chard Bok choyChinese chive Perennial culinary herbsChinese date plum PersimmonChinese long bean Bean

Chinese okra LuffaChinese pear Asian pear Chive Perennial culinary herbsCiku SapodillaClaytonia Salad greensCocoyam TaroCollards Greens for cookingCoriander Annual culinary herbsCorn salad Salad greens

To nd... See...

Crenshaw melon Honeydew melonCustard apple AvocadoDaikon RadishDandelion Salad greensDasheen TaroDate Plum Persimmon

Dill Annual culinary herbsDilly SapodillaDuku LongkongDulian DurianDuren DurianDuyin DurianEddoe TaroElderberry CurrantEscarole Endive and EscaroleField salad Salad greensFilbert Hazelnut

Fire dragon fruit Dragon fruitFlat bean BeanFrench bean BeanFrench sorrel Salad greensGarden sorrel Salad greensGooseberry CurrantGlobe artichoke ArtichokeCollard greens Greens for CookingGombo OkraGreen bean BeanGreen cabbage Cabbage

Green onion OnionGrosse sapote SapodillaGroundnut PeanutGumbo OkraHamburg parsley ParsleyHusk tomato TomatilloJapanese pear Asian pear Java plum Wax appleKadu DurianKale Greens for cookingKang kong Water convolvulus

Kong xin cai Water convolvulusLa pitahaya rouge Dragon fruitLady’s nger Okra

Lamb’s lettuce Salad greensLangsat LongkongLanson LongkongLychee LitchiLong bean BeanLucuma Sapodilla


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To nd... See...

Malanga TaroMalay apple Wax appleMamey SapodillaMandioca CassavaManggistan MangosteenMangis Mangosteen

Mangkhut MangosteenMangostan MangosteenMangostanier MangosteenMangostao MangosteenManggustan MangosteenManioc CassavaMarjoram Perennial culinary herbsMarmalade fruit SapodillaMatai WaterchestnutMelon, Honeydew melon Honeydew melonMelon, Netted Netted melon

Mesetor MangosteenMiner’s lettuce Salad greensMongkhut MangosteenMung bean sprouts SproutsMuskmelon Netted melonMustard cabbage Bok choyMustard greens Greens for cooking Nachi Asian pear Nasberry Sapodilla Néspero Sapodilla Noplaes Nopalitos

Oregano Perennial culinary herbsOriental pear Asian pear Oxheart cabbage CabbageOyster plant SalsifyPak-choy Bok choyPake boong Water convolvulvusPak-tsoi Bok choyPalta AvocadoPaprika Pepper Peppermint Perennial culinary herbsPichi Arazá

Pitahaya Dragon fruitPitaya roja Dragon fruitPod bean BeanQuaio OkraQuingumbo OkraRape Greens for cookingRed beet BeetRian DurianRocket salad Salad greens

To nd... See...

Roquette Salad greensRose apple Wax appleRose water apple Wax appleRosemary Perennial culinary herbsRound sorrel Salad greensRucola Salad greens

Rugula Salad greensRunner bean BeanRupina caspi ArazáSage Perennial culinary herbsSalad chervil Annual culinary herbsSalad pear Asian pear Sand apple Asian pear Sapota SapodillaSapote SapodillaSaurieng DurianSavory Annual culinary herbs

Savoy cabbage CabbageSementah MangosteenSemetah MangosteenSha Li pear Asian pear Shalea pear Asian pear Shallot OnionSnap bean BeanSororia ArazáSorrel Salad greensSpearmint Perennial culinary herbsSpinach Greens for cooking

Sponge gourd LuffaSpring onion OnionSprouting broccoli BroccoliStar apple SapodillaStar fruit CarambolaStinkvrucht DurianStinky rose GarlicStrawberry pear Dragon fruitString bean BeanSugar pea PeaSummer savory Annual culinary herbs

Summer squash SquashSunchokes Jerusalem artichokeSwedes RutabagaSwedish turnips RutabagaSweetsop SapodillaSweet cherry Cherry, sweetSweet pepper Pepper Table beet BeetTaisai Bok choy


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To nd... See...

Tamarindo Tamarind Tangerine Mandarin and TangerineTannier TaroTarragon Perennial culinary herbsThang loy Dragon fruitThureen Durian

Thurian DurianThyme Perennial culinary herbsTree tomato TamarilloTurnip-rooted cabbage Kohlrabi or RutabagaTurnip greens Greens for cookingVegetable oyster SalsifyWater cabbage Water convolvulvusWhite celery mustard Bok choyWhite sapote SapodillaWhitloof ChicoryWinter purslane Salad greens

Winter spinach Water convolvulvusYard-long bean BeanYellow pitaya Dragon fruitYellow wax bean BeanYuca CassavaZapote SapodillaZucchini Squash


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Respiration and Ethylene Production Rates

The values in table 1 are approximations or the average rates of a range; see individual sections on eachcommodity for more specic information and references. Values in parentheses after ethylene rates are the

temperatures at which ethylene production was measured. For respiration data, to get mL kg-1 h-1, dividethe mg kg-1 h-1 rate by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 1.8 at 20 °C (68 °F). To calculate heat production, multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1 or by 61 to get kcal tonne-1 day-1.

Table 1. Rates of respiration and ethylene production _________________________________________________________________________________ RespirationCommodity _________________________________________ C

2H

4 Production

0 °C 5 °C 10 °C 15 °C 20 °C 25 °C _________________________________________________________________________________ —————————— mg kg-1 h-1 ————————- µL kg-1 h-1

Apple Fall 3 6 9 15 20 nd 1 varies greatly

Summer 5 8 17 25 31 nd varies greatlyApricot 6 nd 16 nd 40 nd


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Table 1. Rates of respiration and ethylene production—Continued _________________________________________________________________________________ RespirationCommodity _________________________________________ C

2H

4 Production


Chicory 3 6 13 21 37 nd


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2H

4 Production


Lime nd nd ,10 nd nd nd


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2H

4 Production


Raspberry 176 23 35 42 125 nd ≤12.0 (20 °C)Rhubarb 11 15 25 40 49 nd nd Rutabaga 5 10 14 26 37 nd 100 (20 °C)

Southern Pea Whole Pods 246 25 nd nd 148 nd nd Shelled Peas 296 nd nd nd 126 nd nd Spinach 21 45 110 179 230 nd very lowSprouts (mung bean) 23 42 96 nd nd nd


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Precooling and Storage Facilities

James F. Thompson

Thompson is with the Department of Biological &Agricultural Engineering, University of California,Davis, CA. He is now retired.

In-Field Temperature Management

Temperature management of perishablecommodities begins with proper handling atharvest. Generally, produce should be harvestedin the morning so that it will be at the coolest possible temperature during the delay betweenharvest and initial cooling. Exceptions to thisrecommendation are produce, such as somecitrus fruit, that are damaged if they are handledwhen they are turgid in the morning (Eckert andEaks 1989), or situations in which the produce isharvested in the late afternoon so that it can betransported to a local market during the cool nighthours. Produce should be shaded to protect it fromsolar heat gain. Reduce the time between pickingand initial cooling; this is particularly critical because fruits and vegetables transpire and respireat high rates at eld temperatures (Maxie et al.

1959, Harvey and Harris 1986, d’Sousa and Ingle1989, Robbins and Moore 1992).

Initial Cooling Methods

Produce is usually cooled to its long-term storagetemperature in special facilities designed torapidly remove produce heat.

Forced-air cooling is the most widely adaptablemethod and is commonly used for many fruits,fruit-type vegetables, and cut owers (Parsons et

al. 1970, 1972, Rij et al. 1979, Baird et al. 1988,Thompson et al. 1998).

Hydrocooling uses water as the cooling mediumand is less widely used than forced-air cooling because some products do not tolerate watercontact and because it requires the use of water-resistant packaging. It is commonly used for root-,

stem-, and ower-type vegetables; melons; and

some tree fruits (Pentzer et al. 1936, Toussaint1955, Stewart and Lipton 1960, Bennett 1963,Perry and Perkins 1968, Mitchell 1971).

Vacuum- and water spray vacuum-cooling are usually reserved for crops, such as leafy

vegetables, that release water vapor rapidly,allowing them to be quickly cooled (Barger 1963,Harvey 1963).

Package icing uses crushed ice to cool andmaintain product temperature and is used fora very few commodities, mainly those whose purchasers have a strong traditional demand forthis method. It is still common for broccoli.

Room cooling is accomplished by placing warm

produce in a refrigerated room. Cooling times areat least 24 h and can be much longer if produce isnot packaged correctly or if no provision is madeto allow airow past boxes. It is used for a few

commodities, such as citrus and CA-stored apples,which can have acceptable, though not optimal,quality without use of rapid cooling.

Transport cooling in refrigerated ships andcontainers is used for products, such as bananas,in areas with no cooling infrastructure. Highway

trailers have insufcient airow to cool produceand should never be depended on for initialcooling.

Table 1 is a summary comparison of the six initialcooling methods.


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T a

b l e 1

. C o m p a r i s o n o

f t y p

i c a

l p r o

d u c

t e

f f e c

t s a n d

c o s

t f o r s

i x c o m m o n c o o l

i n g m e

t h o

d s

______________________

___________________________________________________

_________________________________________

F o r c e d - a i r

H y d

r o

V a c u u m

W a t e r s p r a y

I c e

R o o m

______________________

___________________________________________________

_________________________________________

T y p i c a l c o o l i n g t i m e ( h )

1 t o 1 0

0 . 1 t o 1 . 0

0 . 3 t o 2 . 0

0 . 3 t o 2 . 0

0 . 1 t o 0 . 3 *

2 0 t o 1 0 0

P r o d u c t m o i s t u r e l o s s ( % )

0 . 1 t o 2 . 0

0 t o 0 . 5

2 . 0 t o 4 . 0

N o d a t a

N o d a t a

0 . 1 t o 2 . 0

W a t e r c o n t a c t w i t h p r o d u c t

N o

Y e s

N o

Y e s

Y e s , u n l e s s b a g g e d

N o

P o t e n t i a l f o r d e c a y c o n t a m i n a t i o n L o w

H i g h

†

N o n e

H i g h †

L o w

L o w

C a p i t a l c o s t

L o w

L o w

M e d i u m

M e d i u m

H i g h

L o w

‡

E n e r g y e f c i e n c y

L o w

H i g h

H i g h

M e d i u m

L o w

L o w

W a t e r - r e s i s t a n t p a c k a g i n g n

e e d e d N o

Y e s

N o

Y e s

Y e s

N o

P o r t a b l e

S o m e t i m e s

R a r e l y d o n e C o m m o n

C o m m o n

C o m m o n

N o

F e a s i b i l i t y o f i n - l i n e c o o l i n g

R a r e l y d o n e

Y e s

N o

N o

R a r e l y d o n e

N o

______________________

___________________________________________________

_________________________________________

S o u r c e : T h o m p s o n e t a l . 1 9

9 8

* T o p i c i n g c a n t a k e m u c h l o n g e r .

† R e c i r c u l a t e d w a t e r m u s t b e c

o n s t a n t l y s a n i t i z e d t o m i n i m i z e a c c u m u l a t i o n o f d e c a y - c a u s i n g p a t h o

g e n s .

‡ L o w i f p r o d u c t i s a l s o s t o r e d

i n c o o l e r a s i s d o n e w i t h a p p l e s ; o t h e r w i s e l o n g c o o l i n g t i m e s m a k e i t a n e x p e n s i v e s y s t e m .


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Forced-Air Cooling

Refrigerated air is used as the cooling mediumwith this system. It is forced through produce packed in boxes or pallet bins. A number ofairow systems are used, but the tunnel cooler is

the most common (Thompson et al. 1998). Two

rows of packages, bins, or palletized product are placed on either side of an air-return channel. Atarp is placed over the product and the channel,and a fan removes air from the channel, drawingair through the product. The product is cooledin batches. Cooling times range from 1 h for cutowers to more than 6 h for larger fruit, packed in

airow-restricting materials such as bags or paper

wraps.

The cold-wall system is adapted to cooling

smaller quantities of produce (Thompson et al.1998). Individual pallets or cartloads of packagesare placed against a plenum wall. Usually the plenum has a slightly lower air pressure thanthe room, and air is pulled through the product.Some coolers, particularly for cut owers, use a

pressurized plenum and air is pushed through the product. Cold-wall systems do not use oor space

as efciently as tunnel coolers and require more

management because each pallet iscooled individually.

The serpentine air system is designed for cooling produce in pallet bins (Thompson et al. 1998).Stacks of even numbers of bins are placed againsta negative pressure plenum wall. Bottom openingsfor forklift tines are used for air supply and airreturn channels. Air ows vertically up or down

through the product. The forklift openings arelimited in dimension, which restricts airow

and causes slow cooling. This system is used for partially cooling product that will be packaged

later and nish-cooled after packing and forcooling product in long-term storage. The systemuses cold room volume very efciently.

Cooling time in forced-air coolers is controlled by volumetric airow rate and product diameter

(Flockens and Meffert 1972, Gan and Woods1989). Coolers often operate with 1 L kg-1 sec1 of produce, with a typical range of 0.5 to 2.0 L

kg-1 sec-1 (1 L kg-1 sec-1 equals approximately1 CFM lb-1). At 1 L kg-1 sec-1, grapes with asmall minimum diameter will cool in about 2 h,while cantaloupes with a much larger diameterrequire more than 5 h. Boxes should have about5% sidewall vent area to accommodate airow

without excessive pressure drop across the box

(Wang and Tupin 1968, Mitchell et al. 1971).Internal packaging materials should be selected torestrict airow as little as possible.

Forced-air cooling causes some moisture loss.Loss may not be detectable for produce itemswith a low transpiration coefcient, like citrus

fruits, or it may equal several percent of initialweight for produce with a high transpirationcoefcient (Sastry and Baird 1978). Moisture loss

is linearly related to difference between initial and

nal product temperatures. High initial producetemperatures cause higher moisture loss thanlower temperatures when cooling starts. Moistureloss can be reduced at the expense of longercooling times by wrapping product in plastic or packing it in bags.

Details of fan selection, air plenum design,refrigeration sizing, product cooling times, andoperational guidelines can be found in Thompsonet al. (1998). Forced-air coolers are the least

energy efcient type of cooler but are widelyused because they are adaptable to a wide rangeof products and packaging systems (Thompsonet al. 2002). Small units can be installed in manyexisting cold storage facilities.

Hydrocooling

Cooling is accomplished with this technique by moving cold water around produce with a

shower system or by immersing produce directlyin cold water. Shower coolers distribute waterusing a perforated metal pan that is ooded with

cold water from the refrigeration evaporator(Thompson et al. 1998). Shower-type coolers can be built with a moving conveyor for continuousow operation, or they can be operated in a batch

mode. Immersion coolers are suited for producethat sinks in water (Thompson et al. 1998). They


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14

usually cool more slowly than shower coolers because water ows at slower rates past the

product.

Water is a better heat-transfer medium than air,and consequently hydrocoolers cool produce muchfaster than forced-air coolers. In well designed

shower coolers, small diameter produce, likecherries, cools in less than 10 min. Large diameter products like melons cool in 45 to 60 min (Stewartand Lipton 1960, Stewart and Couey 1963,Thompson et al. 1998). Immersion coolers usuallyhave longer cooling times than shower coolers because water speed past produce is slower.

Packages for hydrocooled produce must allowvertical water ow and tolerate water contact.

Plastic or wood containers work well in

hydrocoolers. Corrugated berboard must be wax-dipped to withstand water contact.

Hydrocoolers cause no moisture loss in cooling.In fact, they can rehydrate slightly wilted produce.Hydrocooler water spreads plant decay organismsand thus must be obtained from a clean sourceand treated (usually with hypochlorous acidfrom sodium hypochlorite or gaseous chlorine)to minimize the levels of decay organisms(Thompson et al. 1998).

Calculations of hydrocooler size, refrigerationcapacity, water ow needs, and typical product

cooling times can be found in Thompson et al.(1998). Hydrocoolers can be fairly energy efcient

and are the least expensive cooling method to purchase (Thompson 1992).

Package Icing

Packing a product with crushed or aked ice canquickly cool it and provides a source of coolingduring subsequent handling. It also maintains highhumidity around the product, reducing moistureloss. Its disadvantages are that it has high capitaland operating costs, requires a package that willwithstand constant water contact, and usuallyadds a great amount of weight to the package.

In addition, meltwater can damage neighboring produce in a shipment of mixed commodities.Cut owers are sometimes cooled initially with

a forced-air system, and a small amount of ice ina sealed package is secured in the container. Thisgreatly reduces the amount of ice needed andeliminates meltwater damage, while providing

some temperature control during subsequenttransit and handling.

Vacuum Cooling

This method achieves cooling by causing waterto rapidly evaporate from a product. Water lossof about 1% causes 6 °C (11 °F) product cooling(Barger 1963). Product is placed in a steel vesseland vacuum pumps reduce pressure in the vessel

from 760 mm Hg to 4.6 mm Hg (Thompson et al.(1998). Water boils at a pressure of 20 to 30 mmHg depending on temperature. This causes rapidmoisture evaporation and produce cooling. At theend of the cooling cycle, pressure equals 4.6 mmHg and water boils at 0 °C (32 °F). If the productis held at this pressure long enough, it will cool to0 °C (32 °F). For produce that releases moisturerapidly, like leafy green vegetables, cooling can be accomplished in 20 to 30 min, even whenthe product is wrapped in plastic lm (Cheyney

et al. 1979). The produce loses 2 to 4% of itsweight during cooling, depending on its initialtemperature. Spraying the produce with water before cooling minimizes product moisture loss.Some coolers are tted with water spray systems

that are activated during the cooling cycle.

Procedures for estimating vacuum pump capacity,refrigeration capacity, and condensing coil designcan be found in Wang and Gitlin (undated). UseThompson et al. (1998) and assume a -9 to -7 °C

(15 to 20 °F) refrigerant evaporating temperatureto estimate compressor horsepower. Vacuumcoolers are very energy efcient (Thompson et

al. 1987) and are cost competitive if well utilized(Thompson 1992).


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Marine Transport Cooling

Perishable products should be cooled before being loaded into a refrigerated transport vehicle.However, some production areas do not havecooling facilities, and transport cooling is the onlyfeasible option. Citrus and bananas in the tropics

are often cooled during marine transport.Refrigerated containers and ships supplyrefrigerated air through a oor plenum. Fastest

possible cooling is obtained by using packagesthat allow vertical airow and by loading the

cargo so that refrigerated air is forced through the product. Boxes should have top and bottom vents,and interior packaging materials should not blockair ow. The load or dunnage material must cover

the entire oor to prevent refrigerated air from

traveling up though spaces between pallet loads

and bypassing the load. Proper packaging andloading will allow product to cool in 1 to 2 days(Heap 1998). Improper practices will prevent theload from cooling and the product will arrive atdestination too warm and in poor quality.

Cooling Time Calculations

Rate of cooling is directly related to thetemperature difference between the cooling

medium and the product. Initially, when the product is warm, temperature drops quite rapidly;later, the rate slows as product temperature drops.The product is considered “half cool” when itstemperature drops to half the difference betweenits initial temperature and the cooling mediumtemperature. After another half-cooling period,the product is considered “three-quarters” cool.Product is usually nished cooling at “seven-

eighths” or “fteen-sixteenths” cool. Cooling time

predictions can be done with equations presented

in Thompson et al. (1998) or with a graphicalmethod like that in Sargent et al. (1988).

Cold Storage

Building Design and Layout

The oor area needed for refrigerated storage

can be calculated by determining the maximumamount of product the facility will be expected to

handle in units of volume (m3 or ft3) divided bythe storage height. Storage height is usually about2 m, the height of a pallet load. Product height can be increased by adding pallet racks or, if boxesare strong enough, by stacking pallets up to threehigh. Pallet bins are sometimes stacked to a heightof over 3 m. Add to this area space for corridorsand space for lift truck movement.

Airow Design

Adequate airow is needed to distributerefrigerated air throughout the facility to maintainuniform air temperatures. Most cold storageis designed to have an air ow capacity of 0.3

m3 min-1 tonne-1 of product (100 ft3 min-1 ton1).In long-term storage, the product will reachsetpoint temperature within a few days to about1 week after the facility is lled. Airow can

then be reduced to about 20 to 40% of the designcapacity and still maintain adequate temperatureuniformity. This can be done by intermittent

operation of fans or by keeping the fans constantlyon but reducing their speed with an electronicspeed control system. Slow air speeds reducemoisture loss from the product (Kroca andHellickson 1993).

Airow must be distributed uniformly throughout

the coldroom to minimize temperature variability.For product in pallet loads, one of three systems iscommonly used (Thompson et al. 1998). All threerequire placement of pallets in lanes separated

by 10 to 15 cm (4 to 6 in). In rooms where theair must travel more than 15 m (50 ft), air isdistributed through ceiling ducts or a plenum andreturns to evaporators through a long openingin a plenum wall. Another system distributes airinto the pallet lanes, and the air returns acrossthe ceiling. Pallet bin storage can use the samesystems, or air can be distributed through forkliftopenings or with a serpentine airow system, as is

used in some forced-air coolers.


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pellets. A few products, especially oral and

ornamental crops, can be chemically treated tomake them insensitive to ethylene damage.

Controlled Atmosphere Facilities

Storage rooms can be built for controlled

atmosphere (CA) storage for about 5% additionalcost if they are properly designed initially. Theextra cost is for sealing joints between walls,ceilings, and oors and for installing gas-tight

doors. Tilt-up concrete, metal panels, urethanefoam, and plywood have all been successfullyused as gas barriers. These storage rooms alsoneed equipment for monitoring and controllinggas levels (Waelti and Bartsch 1990).

References

ASHRAE [American Society of Heating,Refrigerating, and Air-Conditioning Engineers].1999. ASHRAE Handbook Series (4 books).ASHRAE, Atlanta, GA.

Baird, C.D., J.J. Gaffney, and M.T. Talbot.1988. Design criteria for efcient and cost-

effective forced-air cooling systems for fruits andvegetables. ASHRAE Trans. 94:1434-1454.

Barger, W.R. 1963. Vacuum cooling: a comparisonof cooling different vegetables. MarketingResearch Report 600, U.S. Department ofAgriculture, Washington, DC.

Bennett, A.H. 1963. Thermal characteristics of peaches as related to hydro-cooling. TechnicalBull. 1292, U.S. Department of Agriculture,Washington, DC.

Cheyney, C.C., R.F. Kasmire, and L.L. Morris.

1979. Vacuum cooling of wrapped lettuce. Calif.Agric. 33:18-19.

Crisosto, C.H., J.L Smilanick, N.K. Dokoozlian,and D.A. Luvisi. 1994. Maintaining Table GrapePostharvest Quality for Long Distance Markets,International Symposium on Table GrapeProduction, American Society for Enology andViticulture, Anaheim, CA.

d’Sousa, M.C., and M. Ingle. 1989. Effect ofdelayed cooling on the poststorage esh rmness

of apples. J. Food Sci. 54:493-494.

Eckert, J.L., and I.L. Eaks. 1989. Postharvestdisorders and diseases of citrus fruits. In W.Ruther, ed, The Citrus Industry, Vol. 5, pp.

179-260, Department of Agriculture and Natural Resources, Pub. no. 3326, University ofCalifornia, Davis, CA.

Flockens, I.H., and H.F.T. Meffert. 1972.Biophysical properties of horticultural products asrelated to loss of moisture during cooling down. J.Sci. Food Agric. 23:285-298.Gan, G., and J.L. Woods. 1989. A deep bedsimulation of vegetable cooling. In V.A. Dodd andP.M. Grace, eds, Land and Water Use, pp. 2301-

2308. Balkema, Rotterdam, The Netherlands.

Harvey, J.M., and C.M. Harris. 1986. In-storagesoftening of kiwifruit: effects of delayed cooling.Int. J. Refrig. 9:352-355.

Harvey, J.M. 1963. Improved techniques forvacuum cooling vegetables. ASHRAE J. 5:41-44.

Heap, R. 1998. Transport of foodstuffs by sea. In R. Heap, M. Kierstan, and G. Ford, eds., Food

Transportation, pp. 75-96. Blackie Academic andProfessional, London, UK.

Kroca, R.W., and M.L. Hellickson. 1993. Energysavings in evaporator fan-cycled apple storages.Appl. Eng. Agric. 9:553-560.

Maxie, E.C., F.G. Mitchell, and A. Greathead.1959. Studies on strawberry quality. Calif. Agric.,Feb. 1:16.

Mitchell, F.G., R.A. Parsons, and G. Mayer. 1971.Cooling trials with plastic tray pack nectarines invarious containers. Calif. Agric. 25(9):13-15.

Parsons, R.A., F.G. Mitchell, and G. Mayer. 1970.Forced-air cooling of palletized fresh fruit. Paper70-875, ASAE, St. Joseph, MI.


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Parsons, R.A. 1972. Forced-air cooling of fruit in bulk bins. SP-01-72:38-41, American Society ofAgricultural Engineers, St. Joseph, MI.

Perry, R., and R. Perkins. 1968. Hydro-coolingsweet corn. Paper 68-800, American Society ofAgricultural Engineers, St. Joseph, MI.

Pentzer, W.T., R.L. Perry, G.C. Hanna, et al. 1936.Precooling and Shipping California Asparagus.University of California Agricultural ExperimentStation Bulletin 600, Univ. of California, Davis,CA.

Rij, R. E., J.F. Thompson, and D. S. Farnham.1979. Handling, precooling, and temperaturemanagement of cut ower crops for truck

transportation. USDA-SEA Adv. Agric. Technol.

AAT-W-5. June.

Robbins, J., and P.P. Moore. 1992. Fruit qualityof stored fresh red raspberries after a delay incooling. HortTechnology 2(4):468-470.

Sargent, S.A., M.T. Talbot, and J.K. Brecht. 1988.Evaluating precooling methods for vegetable packinghouse operations. Proceedings of theFlorida State Horticulture Society 101:175-182.

Sastry, S.K., and C.D. Baird. 1978. Transpirationrates of certain fruits and vegetables. ASHRAETrans. 84(2):237-255.

Stewart, K.S., and H.M. Couey. 1963. Hydro-cooling vegetables—a practical guide to predicting nal temperatures and cooling

times. Mkt. Res. Rpt. 637, U.S. Department ofAgriculture, Agricultural Marketing Service,Washington, DC.

Stewart, J.K., and W.J. Lipton. 1960. Factorsinuencing heat loss in cantaloupes during hydro-

cooling. Marketing Research Report 421, U.S.Department of Agriculture, Agricultural MarketingService, Washington, DC.

Stoecker, W.F. 1998. Industrial RefrigerationHandbook. McGraw-Hill, New York, NY.

Thompson, J.F. 1999. Cold-storage systems. In F.W. Bakker-Arkema, ed., CIGR Handbook ofAgricultural Engineering, vol. IV, pp. 339-361.ASAE, St. Joseph, MI.

Thompson, J.F., F.G. Mitchell, and R.F. Kasmire.2002. Cooling horticultural commodities. In

A.A.Kader, ed., Postharvest Technology ofHorticultural Crops, pp. 97-112. DANR Pub. no.3311, University of California, Davis, CA.

Thompson, J.F., F.G. Mitchell., T.R. Rumsey, et al.1998. Commercial cooling of fruits, vegetables,and owers. DANR Pub. no. 21567, University of

California, Davis, CA.

Toussaint, W.D., T.T. Hatlow, and G. Abshier.1955. Hydro-cooling peaches in the North

Carolina sandhills. Env. Infor. Ser. no. 320, NorthCarolina Agricultural Experiment Station, NorthCarolina State University, Raleigh, NC.

Wang, J.K., and K. Tunpun. 1968. Forced-aircooling of tomatoes in cartons. Trans. Am. Soc.Agric. Eng. 12:804-806.

Waelti, H., and J.A. Bartsch. 1990. CA storagefacilities. In M. Calderon and R. Barkai-Golan,eds., Food Preservation by Modied Atmospheres,

pp. 373-389. CRC Press, Boca Raton, FL.


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Heat Load Calculation

Some factors need to be considered in determining refrigeration required for a cold-storage plant.Examples are simplied to illustrate steps necessary to calculate heat load of a refrigerated storage

area during cooling and normal storage operation. More information on load calculations can be foundin Patchen (1971), Ryall and Lipton (1979), ASHRAE (1981), and Bartsch and Blanpied (1984). Theinformation presented here is adapted from pages 14 to 16 of the previous USDA Agriculture Handbook

Number 66 (Hardenberg et al. 1986). Examples are shown in metric units for pears in storage at -1.1ºC (30 ºF). To convert respiration rate of fruits and vegetables expressed in mg CO

2 kg-1 h-1 to heat

production in kJ, multiply mg CO2 kg-1 h-1 by 61 to get kcal tonne-1 day-1 (1 kcal = 4,186 kJ).

Conditions Example ________________________________ _________________________________________ Storage size 15×15×4.5 mOutside surface area (including oor) 720 m2

Inside dimensions 14.7×14.7×4.2 mVolume 908 m3

Insulation 7.6 cm of polyurethane with a conductivity value

(k) = 1.3 kJ per m2

per cm thickness per ºC; coefcient of transmission (U) = 1.1 kJ h-1 m-2 ºC-1

Ambient conditions at harvest 30 ºC and 50% RHFruit temperature at harvest, 21 ºC; in storage, -1.1 ºCStorage capacity 600 bins at 500 kg fruit per bin = 300,000 kg of fruitBin weight 63.5 kg; total weight of bins = 38,100 kgLoading weight and time 200 bins (100,000 kg fruit per day); 3 days to ll

Cooling rate 1st day, 21 to 4.5 ºC; 2nd day, 4.5 to -1.1 ºCAir changes from door openings: during cooling 6 per day during storage 1.8 per day

Specic heat pears, 0.86; wood bins, 0.5Heat load to lower air: from 30 to -1.1 ºC (50% RH) 74.5 kJ m-3

from 7.2 to -1.1 ºC (70% RH) 15.3 kJ m-3

Miscellaneous heat loads lights, 2,400 W per h (3.6 kJ W-1) fans at 3,112 kJ per HP electric forklifts, 36,920 kJ each for 8 h workers, 1,000 kJ per h per person


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A. Load during cooling and lling storage: temperature difference (TD) from 30 ºC to -1.1 ºC = 31.1

ºC, assuming 31.1 ºC TD on all surfaces:

kJ per 24 h1. Building-transmission load: area (720 m2) × U (1.1 kJ) × TD (31.1 ºC) × h (24) = 591,149

2. Air-change load from doors: vol (908 m3) × heat load (74.5 kJ) × air changes (6) = 405,876

3. Product cooling (eld heat removal): First day Fruit (100,000 kg) × specic heat (0.86) × TD (21 to 4.5 ºC) ×

kJ factor (4.186) = 5,939,934 Bin weight (12,700 kg) × specic heat (0.5) × TD (21 to 4.5 ºC) ×

kJ factor (4.186) = 438,588 Second day Fruit weight (100,000 kg) × specic heat (0.86) × TD (4.5 to -1.1 ºC) ×

kJ factor (4.186) = 2,015,977 Bin weight (12,700 kg) × specic heat (0.5) × TD (4.5 to -1.1 ºC) ×

kJ factor (4.186) = 148,854

4. Heat of respiration during cooling (vital heat): First day Average temperature of 13 ºC; respiration rate of 12,206 kJ per tonne per 24 h; tons of fruit (100) × rate (12,206) = 1,220,600 Second day Average temperature of 1.7 ºC; respiration rate of 1,741 kJ per tonne per 24 h; tonnes of fruit (100) × rate (1,741) = 174,100

Maximum heat accumulated in storage before cooling completed: total fruitweight of 300,000 kg - 2 day loading weight of 200,000 kg = 100,000 kg

(100 tonnes); respiration rate at -1.1 ºC is 812 kJ per tonne per 24 h; tonnesof fruit (100) × respiration rate (812) = 81,200

5. Miscellaneous heat loads:Lights: W (2,400) × kJ per W (3.6) × h (8) = 69,120Fans: HP (3) × kJ per HP (3,112) × h (24) = 224,064Forklifts: 2 × 36,920 kJ per forklift for 8 h = 73,840Labor: workers (2) × kJ per h (1,000) × h (8) = 16,000

Total heat load during cooling:

Building transmission 519,149

Air change 405,876Product cooling 8,543,353Production respiration 1,475,900Miscellaneous 383,024

Subtotal 11,399,302 Add 10% to be cautious 1,139,930 Total required refrigeration 12,539,232


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Assuming refrigeration equipment operates 18 h per day: 12,539,232 ÷ 18 h = 696,624 kJ h-1. Since atonne of refrigeration absorbs 12,660 kJ per 24 h: 696,624 ÷ 12,660 = 55 tonnes of peak refrigerationcapacity is required.

B. Load during normal storage operation (average outside ambient conditions, 7.2 ºC at 70% RH;

storage temperature, -1.1 ºC; TD = 7.2 º to -1.1 ºC = 8.3 ºC).

kJ per 24 h1. Building-transmission load: area (720 m2) × U (1.1 kJ) × TD (8.3 ºC) × h (24) = 157,7662. Air-change load from doors: vol (908 m3) × heat load (15.3 kJ) × air changes (1.8) = 25,006

Product load (respiration, no cooling):

3. Respiration rate at -1.1 ºC is 812 kJ per tonne per 24 h; tonne fruit (300) × rate (812) = 243,600

4. Miscellaneous head loads: Lights: W (2,400) × kJ per W (3.6) × h (4) = 34,560 Fans: HP (3) × kJ per HP (3,112) × h (24) = 224,064 Labor: people (1) × kJ per h (1,000) × h (4) = 4,000

Total load during storage:

Building transmission 157,766Air change 25,006Product load (respiration) 243,600Miscellaneous 262,624

Subtotal 688,996 Add 10% to be cautious 68,899 Total required refrigeration 757,895

Assuming refrigeration equipment operates 18 hours per day: 757,895 ÷ 18 h = 42,105 kJ h-1 and42,105 ÷ 12,660 = 3.3 tonnes of refrigeration capacity is needed during normal storage.

References

ASHRAE [American Society of Heating,Refrigerating and Air Conditioning Engineers].1981. American Society of Heating, Refrigerationand Air Conditioning Engineers Handbook 1982Applications. ASHRAE, Atlanta, GA.

Bartsch, J.A., and G.D. Blanpied. 1984.Refrigeration and controlled atmosphere storagefor horticultural crops. NRAES no. 22, NortheastRegion Agricultural Engineer Service, CornellUniversity, Ithaca, NY.

Hardenburg, R.E., A.E. Watada, and C.Y.Wang. 1986. The Commercial Storage of Fruits,Vegetables, and Florist and Nursery Stocks, pp.14-16. Agriculture Handbook 66, U.S. Departmentof Agriculture, Agricultural Research Service,Washington, DC.

Patchen, G.O. 1971. Storage for apples and pears.Marketing Research Report 924, U.S. Departmentof Agriculture, Washington, DC.

Ryall, A.L., and W.J. Lipton. 1979. Vegetables andmelons. In Handling, Transportation and Storageof Fruits and Vegetables, 2nd ed., vol. 1. AVI Pub.Co., Westport, CT.


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Controlled Atmosphere Storage

Adel A. Kader

Kader was with the Department of Plant Sciences,University of California, Davis, CA. He isdeceased.

Introduction

Controlled atmosphere (CA) storage involvesmaintaining an atmospheric composition that isdifferent from air composition (about 78% N

2,

21% O2, and 0.03% CO

2); generally, O

2 below

8% and CO2 above 1% are used. Atmosphere

modication should be considered as a supplement

to maintenance of optimum ranges of temperatureand RH for each commodity in preserving qualityand safety of fresh fruits, ornamentals, vegetables,and their products throughout postharvesthandling. This chapter gives an overview ofresponses to CA; specic CA considerations are

given in individual commodity summaries.

Biological Basis of CA Effects

Exposure of fresh horticultural crops to low O2 and/or elevated CO2 atmospheres within the

range tolerated by each commodity reducestheir respiration and ethylene production rates;however, outside this range respiration andethylene production rates can be stimulated,indicating a stress response. This stress cancontribute to incidence of physiological disordersand increased susceptibility to decay. ElevatedCO

2-induced stresses are additive to and

sometimes synergistic with stresses caused by low

O2, physical or chemical injuries, and exposureto temperatures, RH, and/or C2H

4 concentrations

outside the optimum range for the commodity.

The shift from aerobic to anaerobic respirationdepends on fruit maturity and ripeness stage(gas diffusion characteristics), temperature,and duration of exposure to stress-inducingconcentrations of O

2 and/or CO

2. Up to a point,

fruits and vegetables are able to recover fromthe detrimental effects of low O

2 and high CO

2

stresses (fermentative metabolism) and resumenormal respiratory metabolism upon transfer toair. Plant tissues have the capacity for recoveryfrom the stresses caused by brief exposureto fungistatic atmospheres (>10% CO

2) or

insecticidal atmospheres (


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maturity and ripeness stage, storage temperatureand duration, and in some cases ethyleneconcentrations.

N2 is an inert component of CA. Replacing N

2

with argon or helium may increase diffusivity ofO

2, CO

2, and C

2H

4, but they have no direct effect

on plant tissues and are more expensive than N2 asa CA component.

Super-atmospheric levels of O2 up to about 80%

may accelerate ethylene-induced degreeningof nonclimacteric commodities and ripeningof climacteric fruits, respiration and ethylene production rates, and incidence of some physiological disorders (such as scald on apples andrusset spotting on lettuce). At levels above 80% O

2,

some commodities and postharvest pathogens suffer

from O2 toxicity. Use of super-atmospheric O2 levelsin CA will likely be limited to situations in which they

reduce the negative effects of fungistatic, elevated CO2

atmospheres on commodities that are sensitive to CO2-

induced injury.

Beneficial Effects of CA (OptimumComposition for the Commodity)—ASummary

• Retardation of senescence (includingripening) and associated biochemicaland physiological changes, particularlyslowing down rates of respiration, ethylene production, softening, and compositionalchanges.

• Reduction of sensitivity to ethylene action atO

2 levels 1%.

• Alleviation of certain physiological disorderssuch as chilling injury of avocado and somestorage disorders, including scald of apples.

• CA can have a direct or indirect effect on postharvest pathogens (bacteria and fungi)and consequently decay incidence andseverity. For example, CO

2 at 10 to 15%

signicantly inhibits development of botrytis

rot on strawberries, cherries, and other perishables.

• Low O2 (1 mo.• Development of off avors and off odors

at very low O2 concentrations (as a result

of anaerobic respiration) and very highCO

2 levels (as a result of fermentative

metabolism).• Increased susceptibility to decay when the

fruit is physiologically injured by too low O2

or too high CO2 concentrations.

Commercial Application of CA Storage

Several renements in CA storage have been made

in recent years to improve quality maintenance.These include creating nitrogen by separationfrom compressed air using molecular sieve bedsor membrane systems, low-O

2 (1.0 to 1.5%)

storage, low-ethylene (


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atmospheric composition around and within thecommodity. Modied atmosphere packaging

(MAP) is widely used in marketing fresh-cut produce.

Applications of CA to cut owers are very limited

because decay caused by Botrytis cinerea is often

a limiting factor to postharvest life, and fungistaticCO

2 levels damage ower petals and/or associated

stem and leaves. Also, it is less expensive to treatowers with anti-ethylene chemicals than to use

CA to minimize ethylene action.

Commercial use of CA storage is greatest onapples and pears worldwide, less on cabbages,

Table 1. Classification of horticultural crops according to their CA storage potential atoptimum temperatures and RH. ________________________________________________________________________________________

Storage duration Commodities _________________________________________________________________________________

Months

>12 Almond, Brazil nut, cashew, lbert, macadamia, pecan, pistachio, walnut,

dried fruits and vegetables

6 to 12 Some cultivars of apples and European pears

3 to 6 Cabbage, Chinese cabbage, kiwifruit, persimmon, pomegranate, somecultivars of Asian pears

1 to 3 Avocado, banana, cherry, grape (no SO2), mango, olive, onion (sweet

cultivars), some cultivars of nectarine, peach and plum, tomato (mature-green)


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Additional Reading and Reference Material

Calderon, M., and R. Barkai-Golan, eds. 1990.Food Preservation by Modied Atmospheres.

CRC Press, Boca Raton, FL.

El-Goorani, M.A., and N.F. Sommer. 1981.

Effects of modied atmospheres on postharvest pathogens of fruits and vegetables. Hort. Rev.3:412-461.

Gorny, J., ed. 1997. Fresh-Cut Fruits andVegetables and MAP, CA’97 Proceedings, vol.5. Postharvest Hort. Ser. no. 19, University ofCalifornia, Davis, CA.

Kader, A.A. 1986. Biochemical and physiological basis for effects of controlled and modied

atmospheres on fruits and vegetables. FoodTechnol. 405:99-100, 102-104.

Kader, A.A., ed. 1997. Fruits Other Than Applesand Pears, CA’97 Proceedings, vol. 3. PostharvestHort. Ser. no. 17, University of California, DavisCA.

Kader, A.A., D. Zagory, and E.L. Kerbel. 1989.Modied atmosphere packaging of fruits and

vegetables. CRC Crit. Rev. Food Sci. Nutr. 28:1-

30.

Mitcham, E.J., ed. 1997. Apples and Pears, CA’97Proceedings, vol. 2. Postharvest Hort. Ser. no. 16,University of California, Davis, CA.

Raghavan, G.S.V., P. Alvo, Y. Gairepy, and C.Vigneault. 1996. Refrigerated and controlledmodied atmosphere storage. In L.P. Somogyiet al., eds, Processing Fruits: Science andTechnology, vol. 1, Biology, Principles and

Applications, pp. 135-167. Technomic Pub. Co.,Lancaster, PA.

Saltveit, M.E., ed. 1997. Vegetables andOrnamentals, CA’97 Proceedings, vol. 4.Postharvest Hort. Ser. no. 18, University ofCalifornia, Davis, CA.

Thompson, A.K. 1998. Controlled AtmosphereStorage of Fruits and Vegetables. CABInternational, Wallingford, U.K.

Thompson, J.F., and E.J. Mitcham, eds. 1997.Technology and Disinfestation Studies, CA’97Proceedings, vol. 1. Postharvest Hort. Ser. no. 15,

University of California, Davis, CA.

Vigneault, C., V.G.S. Raghavan, and R. Prange.1994. Techniques for controlled atmospherestorage of fruit and vegetables. Tech. Bull 1993-18E, Agriculture Canada, Kentville, N.S.

Wang, C.Y. 1990. Physiological and biochemicaleffects of controlled atmosphere on fruits andvegetables. In M. Calderon and R. Barkai-Golan,eds, Food Preservation by Modied Atmospheres,

pp. 197-223. CRC Press, Boca Raton, FL.

Weichmann, J. 1986. The effect of controlledatmosphere storage on the sensory and nutritionalquality of fruits and vegetables. Hort. Rev. 8:101-127.

Yahia, E.M. 1998. Modied and controlled

atmosphere for tropical fruits. Hort. Rev. 22:123-183.

Zagory, D., and A.A. Kader. 1989. Qualitymaintenance in fresh fruits and vegetables bycontrolled atmospheres. In J.J. Jen, ed., QualityFactors of Fruits and Vegetables: Chemistry andTechnology, pp. 174-188. American ChemicalSociety, Washington, DC


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physical injury to the fruit. Papayas grown inHawaii are vapor-heat-treated before beingexported to Japan.

Citrus can be disinfested by HAT at 44 °C (111°F) for 100 min, with an additional 90 minspent raising the temperature to 44°C. The usual

disinfestation method, however, is to hold the fruitat low temperature of 0 to 2 °C (32 to 36 °F) for10 to 16 days before raising the temperature to thenormal storage temperature of 6 to 11°C (43 to 52°F), depending on cultivar. Since citrus is sensitiveto chilling, fruit are generally held at 20 °C (68 °F)or 16 °C (61 °F) for 3 to 5 days before placing atlow temperature. This curing treatment decreasesfruit susceptibility to chilling injury resulting fromthe subsequent disinfestation treatment.

Insect Disinfestation

The development and implementation of heattreatments for insect disinfestation have beenreviewed thoroughly (Couey 1989, Paull 1993).Table 1 includes treatment regimes that have been reported in the past 20 years. More than halfthe treatments are designed to kill fruit y eggs

or larvae, because their presence requires strictquarantine in most fruit-importing countries. The

most recently developed methods include heattreatments in combination with low-O

2 or high-

CO2 atmospheres.

Antifungal Treatments

Curing is used commercially to increase resistanceto pathogen invasion. Potatoes are cured at 12 °C(54 °F) for 10 to 12 days before storage at 4 to 9°C (39 to 48 °F), depending on cultivar and on

whether they are designated for industry or homeconsumption. Sweet potatoes are also cured at 30°C (86 °F) for 5 days before storage at 12 °C (54°F). In both cases the curing period allows forwound healing and deposition of cell wall materialto create a physical barrier to pathogens. Kiwifruitalso benet from a curing period. If held at 10 °C

(50 °F) before storage at low temperatures, they

develop fewer rots after storage. Onions can bestored longer if held at 28 °C (82 °F) for 3 days before storage.

The two commercial applications of high-temperature antifungal treatments are HWT for papayas (Akamine and Arisumi 1953), which has

been used for almost 50 years, and a hot-water brush treatment (HWB) (Fallik 1996a, 1999,Prusky et al. 1997). The brush system is in useon packing lines for export of corn, mangos, peppers, and some citrus from Israel. The machinesprays hot water at 50 to 65 °C (122 to 149 °F) on produce as it moves along on brush rollers. Themajor benet appears to be removal of spores and

dirt, though hot water combined with brushingalso causes surface cracks to be lled in by the

natural wax of the commodity, as well as eliciting

resistance to pathogens in some cases.

The state of temperature conditioning treatmentsagainst fungal pathogens was reviewed by Barkai-Golan and Phillips (1991) and Coates and Johnson(1993). The majority of the regimes listed in table2 were developed in the past 10 years. Dips inhot fungicide solution have been used since the1950s for pathogen control. As various fungicideslose their registration or as pathogens developresistance, there is increased interest in heat-

treating produce in combination with compoundsthat are generally recognized as safe (GRAS),such as calcium chloride or sodium carbonate(table 2).

Physiological Benefits of ConditioningTreatments

Most thermal treatments have been developedas lethal regimes for insects or fungi. Some of

these regimes, however, also have prophylacticeffects against physiological disorders such aschilling injury (CI). Prevention of CI allowsthe commodity to be stored longer at lowertemperatures, which in turn permits export in shipsrather than more costly air freight. In addition,a preshipping heat treatment can allow for low-temperature disinfestations of commodities, such


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T a

b l e 1

. T h e r m a

l t r e a t m

e n

t o

f h o r t

i c u

l t u r a

l c o m m o

d i t i e s

f o r

i n s e c

t d i s i n f e s t a t

i o n

________________________

___________________________________________________________________________________

__________

I n s e c t

L

a t i n n a m e

F r u i t

R e g i m e *

T e m p e r a t u r e / T i m e

R e f e r e n c e

________________________

___________________________________________________________________________________

__________

F r u i t f i e s

C a r i b b e a n f r u i t y

A

n a s t r e p h a s u s p e n s a

g r a p e f r u i t

H A T

S h a r p & G o u l d 1 9 9 4

m a n g o

H A T

5 2 ° C

/ 1 2 5 m i n

M i l l e r e t a l . 1 9 9 1

o r a n g e

H A T

S h a r p & M

c G u i r e 1 9 9 6

M e d i t e r r a n e a n f r u i t y

C

e r a t i t i s c a p i t a t a

a v o c a d

o

H A T

4 0 ° C

/ 2 4 h

J a n g 1 9 9 6

m a n g o

V H T

4 7 ° C

/ 1 5 m i n

H e a t h e r e t

a l . 1 9 9 7

p a p a y a

H A T

4 7 ° C

a t p u l p f o r 3 . 5 h

A r m s t r o n g

e t a l . 1 9 9 5

M e l o n f r u i t y

D

a c u s c u c u r b i t a e

a v o c a d

o

H A T

4 0 ° C

/ 2 4 h

J a n g 1 9 9 6

B

a c t r o c e r a c u c u r b i t a e

c u c u m b e r

H A T t h e n H W T

3 2 ° C

/ 2 4 h t h e n

C h a n & L i n s e 1 9 8 9

4 5

- 4 6 ° C / 5 0 - 6 0 m i n

p a p a y a

H A T

4 C ° C a t p u l p f o r 3 . 5 h

A r m s t r o n g

e t a l . 1 9 9 5

z u c c h i n i

V H T

J a c o b i e t a l . 1 9 9 6

M e x i c a n f r u i t y

A

n a s t r e p h a l u d e n s

g r a p e f r u i t

H A T & C A

4 4 ° C

/ 2 h i n 1 % O 2

S h e l l i e e t a

l . 1 9 9 7

B

a c t r o c e r a c u c u m i s

z u c c h i n i

V H T

4 5 ° C

/ 3 0 m i n

J a c o b i e t a l . 1 9 9 6

O r i e n t a l f r u i t y

D

a c u s d o r s a l i s

c u c u m b e r

H A T t h e n H W T

3 2 ° C

/ 2 4 h t h e n

C h a n & L i n s e 1 9 8 9

B

a c t r o c e r a d o r s a l i s

4 5 - 4 6 ° C / 5 0 - 6 0 m i n

p a p a y a

H A T

4 7 ° C

a t p u l p f o r 3 . 5 h

A r m s t r o n g

e t a l . 1 9 9 5

P a p a y a f r u i t y

B

a c t r o c e r a p a y a p a e

m a n g o

V H T

4 7 ° C

/ 1 5 m i n

H e a t h e r e t

a l . 1 9 9 7

Q u e e n s l a n d f r u i t y

B

a c t r o c e r a t y r o n i

a v o c a d

o

H W T & b e n o m y l

4 6 ° C

/ 3 m i n t h e n

J e s s u p 1 9 9 4

1 ° C / 7 d a y s

l i t c h i

V H T

4 5 �

Documents

The Commercial Storage of Fruits, Vegetables, Florist and Nursery Stocks