Use of Laboratory Data in Freeze Drying Process Design Heat and Mass Transfer Coefficients and the C

Freeze-dryingProcessDesignCristinaRatti22IntroductionFreeze-dryingorlyophilizationisoftenregardedasthebestmethodofwaterremovaltoobtainfinalproductsofthehighestquality.Becauseoftheabsenceofliquidwaterandthelowtemperaturesrequiredfortheprocess,mostofthedeteriorationreactionsandmicrobiologicalactivitiesareprevented,whichgivesafinalproductofexcellentquality.Thesolidstateofwaterduringfreeze-dryingprotectstheprimarystructureandtheshapeoftheproduct,withminimalreductioninvolume.Freeze-driedproductshavealongshelf-lifewithoutrefrigeration,2yearsforaproductwitha2%residualmoisturecontentbeingusual(Williams-Gardner,1971).Thistech-niquehasbeenappliedwithsuccesstodiversebiologicalmaterial,suchasmeat,coffee,juices,dairyproducts,cellsandbacteriaandisnowstandardpracticeintheproductionofpenicillin,proteinhydrolysates,hormones,bloodplasmaandvitaminpreparations.Theapplicationoffreeze-dryingtofoodproductshastraditionallybeenconfinedtotheproductionofheat-oroxygen-sensitivefoodstuffs,orthosefoodshavingaspecialend-usesuchasspacefoods,militaryorextreme-sportfoodstuffsandinstantcoffee(Ratti,2001).Recently,however,themarketfor“natural”and“organic”productshasbeenincreasingstrongly,alongwithconsumerdemandforfoodswithminimalprocess-ingandhighqualitybutwithoutthepresenceofpreservatives.ThemarketforhigherHandbookofFoodProcessDesign,FirstEdition.EditedbyJasimAhmedandMohammadShafiurRahman.©2012BlackwellPublishingLtd.Published2012byBlackwellPublishingLtd.