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ImportanceofTemperatureManagement

AngelosI.Deltsidis,PhD

PostharvestTechnologyCenterUCDavis

Credits:MichaelS.Reid,MaritaCantwell

Outline

• Lowtemperaturestorage–benefits

• Factorsaffectedbylowtemperatures

• Temperaturedisorders• ColdChainandmonitoring• ConsiderationsforSuccessfulCooling/Storage

Lowtemperaturestorage

• ProlongsShelfLife(=maintainsinitialquality)• Slowsdownripening(enzymaticdegradationandrespiratoryactivity)• Preventswiltingbyslowingorinhibitingwaterloss• Slowstherateofproducedecay(slowsorinhibs microbialgrowth)–

MicrobialFoodSafety• Reducesrateofethyleneproduction• Minimizestheimpactofethyleneü Quicklyreachtheoptimumtemperature

• Fastandefficientcoolingafterharvestü Maintainthecoldchain

• Avoidre-warming

Lowtemperaturestorage

• Firststep:removingfieldheat• Secondstep:maintainingasuitablestoragetemperature• Fieldheatisremovedslowlyinlarge,poorlyventilatedroomwithalotofairspace(mostwalk-incoolers-inefficientatremovingfieldheat)

• Fastercoolingtechniques:hydro-cooling,vacuumcoolingandicetoremovefieldheat

• Refrigeratedtrucksaredesignedtomaintainproducttemperature,notreduceit!

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Coolingprinciples

• Harvestedproducealive-respiresevenafteritisdetachedfromplant

• Respirationcannotbehaltedcompletely• objectiveofpostharvestcoolingtoslowtheprocessesandthusincreasestoragelife

• Thehighertheholdingtemperature->thegreatertherespirationrate->thesoonerthequalitybecomesunacceptable

http://www.fao.org/docrep/T0073E/T0073E06.GIF

RelativePerishability

RelativeRespirationRate

NutsDates

CitrusGarlicPotato

AppleCarrotOnion

BananaTomatoPeach

ArtichokeBroccoliStrawberry

AsparagusPeasSweetCorn

10

Credit:MichaelS.Reid

BenefitsofColdStorage• Minimizesproductionlosses

• Weathervariabilitycauseproducetomatureearlierorlaterthanplanned• Allowsproducetobeharvestedontimeandsoldwhenmarketsbecomeavailable

• Improveseconomicsofharvestoperations• Dailyharvestmaybeincreasedsincequalitycanbepreserved->harvestingoveralongerperiod,spreadingoutworkloads• Harvesthourscouldbeextended(effectofambienttemperaturesontheproduceislessened)• Betteruseofequipmentandpersonnel

• Minimizeslossesduringmarketing• Allowsforpostharveststorageofveryperishablecropstobeofacceptablequality(strawberries,leafyvegetables)

• Improvesutilizationbyconsumer• Supplyoftopqualityproducewithlongershelflife->nourgencytoconsumeorprocessproducequicklyafterpurchase• Consumersmorelikelytomakelargerpurchases,enjoylowerhandlingcostsandhavemoretimelyproductutilization

• Expandsmarketopportunities• Allowsproducetomaintainhighqualityandlong/practicalshelflife• Productscompetewithqualityimportsand/orgivesexportopportunities

Temperatureaffectsotherfactorsimportanttoproductlife• Ethylene

• Production• Response

• Waterloss• Woundresponse• Decays• Foodsafety• Unintendedgrowth

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FirstRedRoses

2.5°C 5°C 7.5°C0°C 10°C 12.5°C37°F 41°F 46°F32°F 50°F 55°F

Credit:M.Reid,UCDavis

Cherryshelflife

Credit:M.Reid,UCDavis

PostharvestDecay

0°C 5°C 10°C

7daysofstorage

5°C(41°F) 10°C(50°F)20°C(68°F)

30°C(86°F)40°C(104°F)

Botrytis-2 weeks

5°C(41°F) 10°C(50°F)20°C(68°F)

30°C(86°F)40°C(104°F)

Rhizopus-2 weeks

Credit:M.Cantwell,UCDavis

Alternaria decayfollowingchillinginjury

Alternaria decayfollowingchillinginjury

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Visual Quality Color

Decay Off-odors

2.5∞C 36∞F5∞C 41∞F7.5∞C 45∞F10∞C 50∞F

Spinach:• Commercialwashedandbaggedproduct• Leafdamageisverycommondefect• Leadstoincreaseddecay

But….Targettemp.0°C(32°F)

DamageandDecayImpactofTemperatureonQuality

Credit:M.Cantwell,UCDavis

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Temperaturemanagementandmicrobialfoodsafety• Generallytheproductiscoldestwhenloadedfortransporttodestinationmarkets

• Temperaturemanagementsupplementsgoodsanitationpractices• Lowtempslowspathogengrowthbutprolongspathogensurvival(foodsourcerequired)

• Hightemperatureshortenspathogensurvivaltimeifhumidityislow(i.e.noconsumerpackaging)

• Hightemperature+highhumidity+foodsource=proliferation

Time and Temperature are Amplifiers of Risk

Credit:T.V.Suslow,UCDavis

Days storage

0 3 6 9 12 15 18 21 24 27 30 33 36

Qua

lity s

core

1

2

3

4

5

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9

Asparagus: Deterioration and Temperature

Excellent

Good

Fair

Poor2.5∞C15∞C 10∞C 5∞C

Asparagusstoredathightemperatures

PhotoCredit:LeonardMorris,UCDavis PhotoCredit:CDFA

Whatisthecorrecttemperature?

• Speciesfromcoolclimates• 0– 3°C

• Speciesfromtropicalclimates• 10– 15°C

• Speciesfromsub-tropicalclimates• Varies

• Avocados– 10°C• Kiwi- 0°C

Storedfor1week

Credit:M.Cantwell,UCDavis

ChillingInjury

• Physiologicaldisorderofplantsofsubtropicalandtropicaloriginthatresultsin:

• Reducedquality• Lossofproductutilization

• Temperaturesbetween0and15°C(32-59°F)• CIsymptomsbecomeapparentaftertransfertoambientconditions

Effectofchillinginjury SymptomDiscoloration Internalorexternalorboth,usuallybrownorblackSkinpitting Sunkenspots,especiallyunderdryconditionsAbnormalripening Ripeningisunevenorfails;compositionalchanges,off-flavorsIncreaseindecay Activityofmicroorganisms

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ProductsTemperatureCompatibilityGroups

• Non-chilling sensitive products - store near 0°C (32°F)• Chilling sensitive products - store around 10°C (50°F) - varies

• Occurs at low temperatures above freezing point• Sensitivity, exposure time, temperature

32

27

21

15

96

3 2

0

5

10

15

20

25

30

35

0 2.5 5 7.5 10 12.5 15 - 20

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Temperature°C

StoragelifeofBroccoli

18

24

3033

2624

18

0

5

10

15

20

25

30

35

2.5 5 10 12.5 15 20 - 25

Daysto

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Temperature°C

Storagelifeof“BlackBell”Eggplants

Credit:M.Cantwell,UCDavis0°C(32°F) 5°C(41°F) 10°C(50°F)

Italianbasil– 10daysofstorage

Symptomsofchillinginjury

• Surfacepitting• Watersoaking• Browning• Necrosis• Rots• Poorflavor• Poorripening

0°C 5°C 10°C32°F 41°F 50°F

2Weeksofstorage

Credit:M.Cantwell,UCDavis

Chillinginjury- Serano chiles

Symptomsofchillinginjury

• InternalBreakdown=ChillingInjury

• Mealiness (softbutnotjuicy)

• FleshBrowning• LackofFlavor• FailuretoRipen

CarnivalPeaches

0°C 2.2°C 5°C

7.2°C 10°C

4weeksplus2days@20°C

Credit:C.Crisosto,UCDavis

ChillingSensitivity

Lowestsafetemperature

Commodity

°C °F0-2 32-36 Apple,beetroot,cabbage,carrots,cauliflower,lettuce,leeks,pears,spinach

3 38 Asparagus, cranberry, jujube

4 40 Cantaloupe, certain apple cultivars (McIntosh and YellowNewton), certain avocado cultivars (Booth and Lula), lychee, potato,tamarillo

5 41 Cactus pear, cowpeas, durian, feijoa, guava, kumquat, lima bean, longan, mandarin, orange, pepino

7 45 Certain avocado cultivars (Fuerte and Hass), chayote, okra, olive, pepper, pineapple, pomegranate, snap bean

10 50 Carambola, cucumber, eggplant, grapefruit, lime, mango (ripe), melons (casaba, crenshaw, honeydew, persian), papaya,passion fruit, plantain, rambutan, squash (soft rind), taro, tomato (ripe), watermelon

13 55 Banana, breadfruit, cherimoya, ginger, jackfruits, jicama, lemon, mango (mature-green), mangosteen, pumpkin and hard-rindsquash, sapotes, sweet potato, tomato (mature-green), yam

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Cucumberchillinginjury

Photocredit:YilmazIlker,UCDavis

Chillinginjurysymptoms

Photocredit:BillGrierson,UniversityofFloridaPhotocredit:YilmazIlker,UCDavis

Ethyleneproductionaffectedbystoragetemperatures

• Lowtempscan:• Preventperceptionofethylene

• Preventethyleneresponse

PhotoCredit:DonEdwards,UCDavis

FreezingInjury

• Storagerecommendationsforchillingtolerantcommoditiesslightlyabovethefreezingpoint

• Occurswhenicecrystalsforminthetissues• Cultivars,locations,andgrowingconditionsmayaffectthefreezingpoint

• Highestsafetemperatureshouldbeused• Severityoffreezinginjuryinfluencedbyacombinationoftimeandtemperature

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FreezingInjury

Photocredit:DonEdwards,UCDavis

FreezingInjury

Photocredit:M.Cantwell,UCDavis

HeatInjury

• Hightemperatureconditionsareinjurioustoperishablecrops

•Organsremovedfromtheplantlacktheprotectiveeffectsoftranspiration

• Directsourcesofheat(sunlight)canelevatethetissuetemperaturestoabovethethermaldeathpointoftheircells,leadingto:

• localizedbleaching• necrosis(sunburnorsunscald)• generalcollapse

Directsunexposurereducesmarketablequality

0d

Storage7d7.5°C

Shelf7d7.5°C

+2d20°C

0.5h 1.0h 1.5h

(producttemperaturereached50°C-122°Fafter1hour)

PhotoCredit:M.Cantwell,UCDavis

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Hightemperatureeffectsontomatoes

20°C 25°C 30°C 35°C

PhotoCredit:AdelKader,UCDavis

2weektomatostorage

PhotoCredit:DonEdwards,UCDavis

CantaloupeMeloncoolingdelays

Qualityevaluatedafterstoragefor14dat5°C

Generallyfornettedmelonsrecommend<4hoursdelaytocool

X Data

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X Data

% w

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Hours at 30∞C

% S

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A. Visual Quality

C. % Soluble solids

B. % Weight loss

Hours at 30∞C

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DELAYSTOCOOL• Allowformicrobialgrowth• Allowcriticalweightloss• Allowmetabolicchanges• Incurringcostswithoutfull

benefitofcoolingoperation

Credit:M.Cantwell,UCDavis

ManagetheNeedtoCool• Coolingbeginsinthefield• Harvestearly• Keepproductshaded• Transportfrequentlytocooler

• Reducedelaystocool• 1hourdelaytocool=1lessdayshelf-life

• Coordinateharvestandcooling

Night harvest of cantaloupes

Field packed melons waiting to be cooled

Field packing lettuce on shaded mobile platform Shaded reception for berries

Field packing green beans—what is wrong here?

Credit:M.Cantwell,UCDavis

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CoolingDelays

Hours delay to cool (30∞C, 86∞F) 0 2 4 6 8

Perc

ent

0

20

40

60

80

100

0

20

40

60

80

100% Marketable Strawberries after 7 days 5∞C, 41∞F

Credit:M.Cantwell,UCDavis

• Itismoreimportanttoreducedelaystocoolthantousethemostrapidmethodofcooling

• Delayspermitted(minimalpostharvestimpact):• Berries<2hrs (decay)• Lettuces<4hrs (pinkingdecay)• Broccoli<3hrs (firmness)• Pepper<3hrs (firmness)• Eggplant<3hrs (gloss)• Melon<4hrs (futurebrowning)

RelativeHumidity(RH)

• RHinfluences:• waterloss• decaydevelopment• incidenceofsomephysiologicaldisorders• uniformityoffruitripening

• AppropriateRHrangeforstorageoffruitsis85to95%whilethatformostvegetablesvariesbetween90and98%.

• OptimalRHrangefordryonionsandpumpkinsis70to75%.Somerootvegetables,suchascarrot,parsnip,andradish,canbestbeheldat95to100%RH.

RelativeHumidity(RH)considerations

• Freshproducecontinuestotranspireandlosewaterafterharvest• HighRHinthestorageatmospherereduceswaterloss

• canbedifficulttoachievedependingonairexchangerates

• MostrefrigerationsystemsoperateatlowRH(arapiddryingeffect)• FreshproducecoolingfacilitiesneedtobeespeciallydesignedtoprovidewatervapormanagementatahighRH

ConsiderationsforSuccessful

Cooling:• Timebetweenharvestandpre-cooling

• Typeofcarton,pallet;ventilation• Coolingmethodandtimeallowed• Initialproducttemperature• Finalproducttemperature• Sanitationofcoolingmethod• Maintainproducttemperature

Coldstorage:• Expectedstoragelifeordegreeofperishability

• Temperature• Relativehumidity• Sensitivitytochillinginjury• Sensitivitytoethylene

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ColdChain

• Allthecriticalstepsandprocessesthatperishableproductsmustundergoinordertomaintaintheirquality

• Itisonlyasstrongasitsweakestlink

• Issuesexperiencedbythecold-chain:poortemperaturemanagementduetoeitherthelackof,orlimitationsin,refrigeration,handling,storage,andhumiditycontrol

MaintainingTheColdChainForPerishablesHarvest • Minimize delays before cooling

• Cool the product thoroughly as soon as possibleCooling • StoretheproductatoptimumtemperatureTemporaryStorage • Practice first in first out rotation

• Ship to market as soon as possible

TransporttoMarket • Use refrigerated loading area• Cool truck before loading• Avoid delays during transport• Load pallets towards the center of the truck• Putinsulatingplasticstripsinsidedoorofreefer iftruckmakesmultiplestops• Monitorproducttemperatureduringtransport

Handlingatdestination • Use a refrigerated unloading area• Measure product temperature• Move product quickly to the proper storage area• Transport to retail markets or foodservice outlet• Operations in refrigerated trucks• Display at proper temperature range

Handlingathomeorfoodserviceoutlet

• Store product at proper temperature• Use the product as soon as possible

Temperaturemonitoringtools

• Dataloggers• Time/temperature labels• Active RFID

Innovationishere!

• Wirelesstemperaturesensorsforeasyinstallationandrelocation

• 7– 10yearbatterylife• Washable,NSF-certifiedsensorsforuseinfoodhandling

• Intuitivesoftwareforeasysystemmanagement

• AutomatedemailandSMSalertsforquicknotificationandresponse

• Intelligentmanagementofexpectedbehaviorssuchasdefrostcycles

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TemperatureandotherPostharvestRecommendations• http://postharvest.ucdavis.edu(variousdates)ProduceFacts.RecommendationsforMaintainingPostharvestQuality

• http://www.ars.usda.gov/is/np/CommercialStorage/CommercialStorage.pdf

USDAAgricultureHandbookNumber66;TheCommercialStorageofFruits,Vegetables,andFloristandNurseryStocksPrintedversion2016

Thanksforyour

attention