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1、ShelfLifeTesting:ProceduresandPredictionMethodsforFrozenFoodsBinFuKellogg'sBattleCreekMITheodoreP.LabuzaDept.ofFoodScience&Nutrition,UniversityofMinnesota1334EcklesAve.,St.Paul,MN55108219.1IntroductionTheshelflifeofafoodcanbedefinedasthetimeperiodwithi
2、nwhichthefoodissafetoconsumeand/orhasanacceptablequalitytoconsumers.Justlikeanyotherfood,frozenfoodsdeteriorateduringstoragebydifferentmodesormechanisms,assummarizedinTable1.Microbesusuallyarenotaproblemsincetheycannotgrowatfreezingtemperaturesunlesssu
3、bjectedtoextensivetemperatureabuseabovethefreezingpoint.Enzymesareabigconcernforfrozenfoods,whichcancauseflavorchange(lipoxygenase)innon-blanchedfruitsandvegetablesandaccelerateddeteriorationreactionsinmeatandpoultry(enzymesreleasedfromdisruptedmembran
4、esduringprecooking).Celldamageorproteinandstarchinteractionsduringfreezingcausedripandmushinessuponthawing.Discolorationcouldoccurbynon-enzymaticbrowning,bleaching,andfreezerburn.VitaminClossisoftenamajorconcernforfrozenvegetables.Physicalchanges,sucha
5、spackageiceformation,moistureloss,emulsiondestabilization,recrystallizationofsugarsandiceoffrozendessertsareoftenacceleratedbyfluctuatingtemperatures.Foranyspecificfrozenproduct,whichmodedeterminesitsshelflife,dependsontheproductcharacteristics(rawmate
6、rials,ingredients,formulation),pre-freezingtreatment,freezingprocess,packagingfilmandprocesses,andofcoursestorageconditions.Allofthequalitydeteriorationandpotentialhazardsareusuallyexaggeratedorcomplicatedbyafluctuatingtime-temperatureenvironment(e.g.f
7、reeze/thawcycle)duringstorage.Ontheotherhand,theshelflifeofafrozenfoodcanbeextendedthroughingredientselection,processmodificationandchangeofpackageorstorageconditions,asdiscussedinSection3ofthisbook.Thischapterwillfocusonshelflifetestingoffrozenfoodsfo
8、rproductdevelopmentandmarketpractices.Shelflifetestingconsistsbasicallyofselectingthequalitycharacteristicswhichdeterioratemostrapidlyintimeandthemathematicalmodelingofthechange.Table19.1canbeusedasareferencefortheselectionofqualitychar
