Freeze Drying

Sanjana BhattacharyyaChemical EngineeringB. Tech. 3rd YearRoll: 115537Freeze DryingTechnique to dry materials better than conventional methodsRemoves up to 99% of moistureUsed extensively in food, pharmaceutical and chemical industriesTechnique developed during WWII to transport serumINTRODUCTIONWater frozen below 0CReheated at pressure below 0.6 atmDirect sublimation occursBASIC PRINCIPLE

Consists of 4 parts:PretreatmentFreezingSub-coolingIce nucleationCrystallizationMECHANISM OF FREEZE DRYING-I

Primary dryingIce crystals sublimate, ice front moves back7-8% moisture remainsPartial vacuum maintained

MECHANISM OF FREEZE DRYING-II

Secondary dryingBound moisture removed by desorption2-1.5% moisture remains

MECHANISM OF FREEZE DRYING-III

WORKING OF A FREEZE DRYER

Arose in late 1970s due to economic crisisPopularized by freeze-dried ice creamLight and convenient as emergency food supplyFreeze-dried fruits sold as popular snacksHealthier alternative of processed pet food

APPLICATIONS: FOOD INDUSTRY-I

Fresh look and flavours remain intactNutrients are frozen intactShelf life 25+ yearsNo additivesEasier to rehydrate because of tiny pores

APPLICATIONS: FOOD INDUSTRY-II

Shelf life of life saving medicines increasedHeat sensitive drugs and biologics can be destroyed on drying at high temperatureFreeze dried products can be restored quickly and easily in emergenciesUsed in vaccines, antibodies, penicillin, enzymes, hormones etc.Freeze dried blood has great potentialAPPLICATIONS: PHARMACEUTICALS-IUsed in restoring paper based documents damaged by waterWater logged artifacts can be recovered for museumsUsed in taxidermy for pets and hunting trophiesUsed to preserve flowers and petals for decorations

OTHER APPLICATIONSCan be made more time and energy efficientCan be economized for commercial usesDevelopment of better anti-freeze materials will reduce mechanical injury to cellBetter stability can be provided in final product, especially biologics

POSSIBLE IMPROVEMENTSCONCLUSIONTHANK YOU!