Freeze drying ppt

FREEZE DRYING

1. -: Presented by :-
Monika K. Tambakhe
Dr. P.A. Pawar
University Department of Chemical Technology, Sant Gadge baba
Amravati University ,Amravati. Maaharashtra,INDIA.444602.
Email [email protected]
[email protected]

2. INTRODUCTION
Freezedryingisarelativelyrecentmethodofpreservingfood.
Althoughitisnotwidelyusedinthefoodindustryduetohigh
operationcosts,newimprovementssuchasadsorption,
fluidization,andmicrowavehavebeenresearchedinorderto
reducecosts.
Itisthemostimportanttechniquetodrycoffee,enzymes,food
ingredients,highvaluefoods.
Thisprocesscouldbeconsideredasavaluablealternativeto
preservefoods.

3. INTRODUCTION
Stabilizationofenzymaticsystems,newingredientsinthe
fieldoffunctionalfoods,andexoticfoodsareexamplesofnew
applicationsofthistechnology.
Inageneralway,freeze-dryingorlyophilization,istheprocess
ofremovingwaterfromaproductbysublimationand
desorption.
Sublimationisthetransformationoficedirectlyintoagas
withoutpassingthroughaliquidphase.Sublimationoccurs
whenthevaporpressureandthetemperatureoftheice
surfacearebelowthoseofthetriplepoint(4.58mmHg,0ºC),
asshowninthepressure-temperaturephasediagramofpure
water(Figure1).

4. INTRODUCTION
FigureNo.1-Pressure-temperaturephasediagramofpure
waterandzonesofprocessesforphasechanges

5. INTRODUCTION
Inshort,freezedryingisamultipleoperationinwhichthe
materialtobestabilizedis-
1.Frozenhardbylow-temperaturecooling
2.Driedbydirectsublimationofthefrozensolventandby
desorptionofthesorbedorboundsolvent,generallyunder
reducedpressure.
3.Storedinthedrystateundercontrolledconditions.

6. INTRODUCTION
However,freezedryingisanexpensiveformofdehydration
forfoodsbecauseoftheslowdryingrateandtheuseof
vacuum.Thecostofprocessingisoffsettosomeextentby
theabsenceofanyneedforrefrigeratedhandlingand
storage.
Increasingly,freezedryingisusedfordehydratingfoods
otherwisedifficulttodry,suchascoffee,onions,soups,and
certainseafoodsandfruits.Freezedryingisalsoincreasingly
employedinthedryingofpharmaceuticalproducts.

7. INTRODUCTION
Difference between Conventional drying and freeze drying

8. HISTORY-
ThehistoryoffreezedryinggoesbacktotheancientInca’s,
whopreservedtheirfoodstuffbyfreezingitinthemountains
inwintertime.Atthesametimethefrozenwaterisremoved
throughthelowvaporpressureofthewaterinthe
surroundingairatthosehighaltitudes.
Ofcoursethisprocesswasratherslow,butduringthedrying
processthequalityofthefoodwasmaintainedduetoits
frozenstate.Oncedriedthefoodmaterialslikepotatoesand
vegetablesshowedaremarkablyincreasedqualityovertime.

9. HISTORY-
Especiallytheneedforimprovingshelflifeof
pharmaceuticalslikepenicillinandthepreservationofblood
plasmainwartimewasadriveforthedevelopmentofthe
moderntray-typeLyophilizerasitisstillusedinmany
industriestoday.
Anothercatalystforthedevelopmentofthefreezedry
technologywasthesurplusofcoffeeincountrieslikeBrazilin
thelate30’softhepreviouscentury.

10. HISTORY-
Alsoherethetray-typefreezedryerwasusedforthe
sublimationofthewaterfromthefrozencoffeegranules.
BrandnameslikeNescafewerefoundedatthattime.Instant
coffeeisnowthemostwell-knownfreezedriedproduct.
Afterthewarperiodthetechnologyemergedintoitscurrent
popularityforthedryingofmanydifferenttemperature
sensitivematerialslikepharmaceuticalsandfoodmaterials.
Thereexistalready400differentfreezedriedfoodmaterials
alone.

11. FREEZE DRYING PROCESS -
Freezedryingisaprocessbywhichasolvent(usually
water)isremovedfromafrozenfoodstufforafrozen
solutionbysublimationofthesolventandbydesorptionof
thesorbedsolvent(nonfrozensolvent),generallyunder
reducedpressure.Thefreezedryingseparationmethod
(process)involvesthefollowingthreestages:
(a)thefreezingstage,
(b)theprimarydryingstage,and
(c)thesecondarydryingstage.

12. FREEZE DRYING PROCESS -
FigureNo.2–Diagramofamaterialonatrayduringfreeze
drying.
The variable X denotes the position of the sublimation

13. FREEZINGSTAGE-
Thefreezingstagerepresentsthefirstseparationstep
inthefreezedryingprocess,andtheperformanceofthe
overallfreezedryingprocessdependssignificantlyon
thisstage.Thematerialsystemtobeprocessed(e.g.,gel
suspension,liquidsolution,orfoodstuff)iscooleddown
toatemperature(thistemperaturedependsonthe
natureoftheproduct)thatisalwaysbelowthe
solidificationtemperatureofthematerialsystem.
Theobjectiveofthefreezingstageistofreezemostof
thewateroriginallypresentintheproductforits
posteriorsublimation.

14. PRIMARYDRYINGSTAGE
Afterthefreezingstage,thedryingchamberwheretheproduct
isplacedisevacuatedandthechamberpressureisreducedtoa
valuethatwouldallowthesublimationofsolvent(water)totake
placeintheprimarydryingstage.
Whenthewatermoleculessublimeandenterthevaporphase,
theyalsokeepwiththemasignificantamountofthelatentheat
ofsublimation(2840kJ/kgice)andthusthetemperatureofthe
frozenproductisagainreduced.
Ifthereisnoheatsuppliedtotheproductbyaheatsource,then
thevaporpressureofthewateratthetemperatureoftheproduct
reachesthesamevalueasthatofthepartialpressureofthewater
vaporinthedryingchamber;therefore,thesystemreaches
equilibriumandnoadditionalwatersublimationfromtheproduct
wouldoccur.

15. PRIMARYDRYINGSTAGE
Thewatervaporproducedbythesublimationofthefrozen
waterinthefrozenlayerandbythedesorptionofsorbed(non
frozen)waterinthedriedlayerduringtheprimarydrying
stagetravelsbydiffusionandconvectiveflowthroughthe
porousstructureofthedriedlayerandentersthedrying
chamberofthefreezedryer.(Itshouldbenotedthatmostof
thewaterremovedduringtheprimarydryingstageis
producedbysublimationofthefrozenwaterinthefrozen
layer.)
Thetimeatwhichthereisnomorefrozenlayeristakento
representtheendoftheprimarydryingstage.

16. SECONDARY DRYINGSTAGE
Thesecondarydryingstageinvolvestheremovalofwaterthat
didnotfreeze(sorbedorboundwater).Inanidealfreezedrying
process,thesecondarydryingstagestartsattheendoftheprimary
dryingstage.
Inthesecondarydryingstage,theboundwaterisremovedby
heatingtheproductundervacuum;theheatissuppliedtothe
productusuallybyconduction,convection,orradiation.The
followingproducttemperaturesareusuallyemployed:(a)between
10and35Cforheatsensitiveproductsand(b)50Cormorefor
less-heat-sensitiveproducts.
Theresidualmoisturecontentinthedriedmaterialatthe
endofthesecondarydryingstage,aswellasthetemperature
atwhichthedriedmaterialiskeptinstorage,arecritical
factorsindeterminingproductstabilityduringitsstoragelife.

17. HEAT AND MASS TRANSFER IN FREEZE-DRYING -
Rateofheattransfer-
Therearethreemethodsoftransferringheattothe
sublimationfront.
1.Heattransferthroughthefrozenlayer
2.Heattransferthroughthedriedlayer
3.Heatingbymicrowaves
Heat Source
Condenser
Mass
Transfer
Heat
Transfer
Frozen
Portion
part
Dry
Portion
part

18. Rate of mass transfer-
Whenheatreachesthesublimationfront,itraisesthe
temperatureandthewatervapourpressureoftheice.
Vapourthenmovesthroughthedriedfoodtoaregionof
lowvapourpressureinthedryingchamber.
Thefactorsthatcontrolthewatervapourpressuregradient
are:
thepressureinthedryingchamber
thetemperatureofthevapourcondenser,bothof
whichshouldbeaslowaseconomicallypossible.
thetemperatureoficeatthesublimationfront,which
shouldbeashighaspossible,withoutmelting.

19. (a)Heat transfer through frozen layer
(b)Heat transfer from hot surfaces through dry layer
(c)Heat generated in ice by microwaves

20. COMPONENTS OF A FREEZE -DRYER -
Figure: Components of freeze dryer

21. COMPONENTS OF A FREEZE -DRYER -
Thedryingchamber,inwhichthesampleisplacedand
heating/coolingtakesplace,mustbevacuumtightandwith
temperaturecontrolledshelves.
Thecondensermusthavesufficientcondensingsurfaceand
coolingcapacitytocollectwatervaporreleasedbythe
product.Asvaporscontactthecondensingsurface,theygive
uptheirheatenergyandturnintoicecrystalsthatwillbe
removedfromthesystem.Acondensertemperatureof-65ºC
istypicalformostcommercialfreezedryers.
Thevacuumpumpremovesnon-condensablegasestoachieve
highvacuumlevels(below4mmHg)inthechamberand
condenser.
Theheatsourceprovidesthelatentheatofsublimation,and
itstemperaturemayvaryfrom–30to150ºC.

22. In the freeze drying plant, three process sections are
especially energy consuming.
Processsection1involvesthefreezingofthewetproduct.As
thisisnormallyconsideredoneofthepreparatorysteps
beforethefreezedryingproper,wewillconcentrateonthe
othertwothattakeplaceinthefreezedryingcabinet.
Processsection2involvesthecontrolledsupplyofheatto
theproducttocoverrequirementsforthesublimationand
desorptionprocesses.
Processsection3involvestheremovalfromthefreeze
dryingchamberofthevastvolumesofwatervaporreleased
dryingthesublimationanddesorptionprocesses.Ofthese
threeprocesssections,removalofthewatervapouralways
consumesthelargestamountofenergy.Theefficiencyof
watervaporremoval,thevaportrapsystem,thereforehasa
decisiveeffectonthetotalenergyconsumptionofthefreeze
dryingplant.
FREEZE DRYING PLANTS AND EQUIPMENT
-

23. 1.Pilotfreezedrying
2.Industrialfreezedrying
a.TrayandPharmaceuticalFreezeDryers
b.MultibatchFreezeDryers
c.ContinuousFreezeDryers
d.TunnelFreezeDryers
e.Vacuum-SprayFreezeDryers
FREEZE DRYING PLANTS AND
EQUIPMENT -

24. 1. PILOTFREEZEDRYING
Freezedryingpilotunitsappropriateforuseinthe
pharmaceuticalandfoodindustries,aswellasinthe
laboratory,areinhighdemandbecausetheyareusedto
explorepossibilitiesforthepreservationoflabileproducts,
especiallywiththoseofbiologicalorigin.
Theycanfreeze-drybatchesconsistingoffrom2to20kgof
frozenproduct.
Theunitconsistsof
(a)afreezingfluidsystemthatcanbesenttotheheat
exchangerinthesectionofthecondenserorintothe
refrigerationcoilsforproductfreezing,
(b)aheatingcircuit(siliconoilistheheatingfluid)forplate
heatinganddefrostingofthecondenser,and
(c)avacuumsystemforevacuatingairfromtheapparatus
beforeandduringdrying.

25. 1. PILOTFREEZEDRYING
Figure : Pilot Freeze dryer

26. 2. INDUSTRIALFREEZEDRYING-
(a)Tray and Pharmaceutical Freeze Dryers:
Byfarthelargestnumberoftheindustrialfreezedryers
inoperationisofthevacuumbatchtypewithfreezedryingof
theproductintrays.Therearetwomaintypes,dependingon
thetypeofcondenserused.Inthefirsttype,thecondenser
platesarealongsidethetrayheaterassemblyandinthesame
chamber;inthesecondtypethecondenserisinaseparate
chamberjoinedtothefirstbyawide,ingeneral,butterfly
valve.Thislattertypeofplantisalwaysusedinpharmaceutical
industries,butitcanalsobeusedforthefreezedryingoffoods.

27. (b)Multibatch Freeze Dryers :
Thefreezedryingprocessinabatchplantisnormally
programcontrolledtominimizethedryingtimeandto
maximizetheproductionoftheplant.Withasingle-batch
planttheloadonthevarioussystemswillbeveryvariable
throughoutthedryingcycle.
Theoptimalutilizationofresourceswillnotbepossibleina
single-cabinetbatchplant.
Theextentofthisdisadvantagecanbeeliminatedwhenan
industrialfreezedryingplantisbuiltwithanumberofbatch
cabinets.Thismakespossiblethesimultaneousproductionof
differentproducts,whichincreasestheoperationflexibilityof
theplant.
Alargenumberofindustrialfreezedryingplantsoperate
todayinthiswayasmulti-cabinetbatchplants.

28. Batch freeze dryer

29. (c)Continuous Freeze Dryers :
Recentyearshaveshownagrowinginterestinfreeze
dryingplantsoperatingwithacontinuousflowofmaterial
throughtheprocess.Particularlyinindustriesworkingwitha
singlestandardizedproductandthepreparationofthe
productisbyacontinuousprocess,suchplantsarereally
profitable.
Theygivecontinuityinprocessingthroughoutandconstant
operatingconditionsthatareeasilycontrolled,andthey
requirelessmanualoperationandsupervision.
Continuousfreezedryersareusedforfreezedryingof
productintraysandforfreezedryingofagitatedbulk
materials.

30. Continuous freeze dryer

31. (d)Tunnel Freeze Dryers :
Largecommercialplantsforprocessingcottagecheeseandcoffee
havebeenbuiltupinthisway.Thetunnelfreezedryershavethe
sameadvantagesofplantcapacityutilizationthatcanbeachievedas
inmulti-batchplants,buttheflexibilityforsimultaneousproduction
ofdifferentproductsorinswitchingfromoneproducttoanotheris
lacking.
Inthetunneltypeoffreezedryer,
theprocesstakesplaceinalarge
vacuumcabinetintowhichthe
tray-carryingtrolleysareloadedat
intervalsthroughalargevacuum
lockatoneendofthetunneland
dischargedsimilarlyattheother
end.

32. (d)Tunnel Freeze Dryers :

33. (e)Vacuum-Spray Freeze Dryers:
Thisdryerhasbeendevelopedforcoffeeextract,tea
infusion,ormilk.Theproductissprayedfromasinglejet
upwardordownwardinacylindricaltowerof3.7mdiameter
by5.5mhigh.Theliquidssolidifyintosmallparticlesby
evaporativefreezingThewholeplantoperatesundera
vacuumofabout67Pa.Frozenparticlesobtainedbyspraying
intoavacuumareabout150mmindiameterandloseabout
15%moistureintheinitialevaporation.Thereisnostickingof
theseparticles.

34. Vacuum spray freeze dryer

35. THE MANUFACTURING PROCES -

36. THE MANUFACTURING PROCES -
Raw Materials :
•Somefoodsareextremelywell-suitedtothefreeze-
dryingprocess;othersdonotfaresowell.Liquids,thin
portionsofmeat,andsmallfruitsandvegetablescanbe
freeze-driedeasily.Coffeeisthemostcommonfreeze-
driedliquid.
• Thickportionsofmeatandlarger,wholevegetables
andfruitscannotbefreezedriedwithanysuccess
Testingandpreparation:
•Thefoodisfirstcheckedforcontaminationandpurity.
•Somekindsoffood,likeseafoodandmeats,mustbe
cookedbeforefreezedrying.

37. THE MANUFACTURING PROCES -
Freezing:Temperatureisaslowas-40F(-40C).Inthis
extremelycoldtemperature,thefoodisquicklyfrozen.
Drying:Thecartsarewheeledoutofthecoldroomandintoa
vacuumdryingchamber.Inalargeplant,theremaybe20to30
dryingchambersinoperationatanytime.Thedryingprocedure
involvesasublimationprocess.
Sizingandblending:Somefoodpiecesmaybegroundtoa
smallersizeormaybereducedtoapowder.Othersmaybe
screenedtoseparatethembysize.Twoormoredifferent
productsmayalsobeblendedtogethertomeetacustomer's
specificspecifications.
Packing:Freeze-driedfoodsmustbesealedinairtight
containerstopreventthemfromabsorbingmoisturefromthe
air.Severaltypesofcontainersmaybeused:plasticlaminated
foilpouches,metalandplasticcans,ormetalandfiberdrumsfor
bulkpackaging.Somefreeze-driedfoodisvacuumpacked,in
whichtheairisevacuatedfromthecontainerbeforesealing.

38. QUALITY CONTROL -
Eachfoodhasdifferentprocessing,storage,and
rehydrationrequirements.
Atlargefreeze-dryingfacilities,electronic
microprocessorsregulatethetimes,temperatures,and
pressuresthroughouteachstepoftheprocess.
Acentralcomputercollectsthisdata,analyzesitusing
statisticalqualitycontrolmethods,andstoresitfor
laterreference.
Thisassuresthatthefoodsentouttothepublicfor
consumptionhasbeenthroughastrictlycontrolled
processthatmeetsgovernmentguidelinesandvaries
onlyslightlyfrombatchtobatch

39. Figure :Effect of freezing-rate and heating temperature on freeze-drying
rate of “guacamole”
INFLUENCE OF PARAMETERS -

40. INFLUENCE OF PARAMETERS -
1.Freezingrate:Influenceontheiceconfigurationandthuson
thefinalstructureofthefreeze-driedproduct
2.Heatflux:toreducedryingrate.However,ifthedrying
proceedstoorapidly(highheatflux),theproductmaymelt,
collapseorcanbeblownoutofthecontainerExcessiveheat
maycausethedrycaketocharorshrink.
3.Chamberpressure:Chamberpressureaffectsthetransport
properties,thermalconductivityandwatervapordiffusivity.
4.Temperature:affectingthequalityoffreeze-driedproducts.
Maintaininglowtemperaturesduringprimarydryingwill
reducearomalosses.Ifthetemperatureoficeinthecondenser
ishigherthanproduct’stemperature,watervaporwilltendto
movetowardtheproduct,anddryingwillstop.

41. Freezedryingiscostlybecauseofthelongdryingtimes
involved;thisfactorhashinderedtheapplicationofthe
techniquetodryingofmaterialsinbulk.
Fixedcost-Theaveragefixedcostisgivenbytheratioof
theannualfixedcosttotheannualcapacity.
Runningcost-Therunningcostconsistsoflaborand
utilitiescosts.Theutilitiescostcanbeestimatedfroma
heatandenergybalancefor1-kgwaterundergoing
freezing,sublimation,condensation,andmelting.
FREEZE DRYING COSTS -

42. MOST FREEZE DRIED FOODS -
Freeze dried coffee-
Typesoffreezedried
coffee:
•100%PureCoffee
•Decaffeinated
•Flavoured
•Organic
•FairtradeCoffee
•RainforestCoffee
•DualCertifiedCoffee
•TripleCertifiedCoffee

43. Freeze Dried Strawberries-
Freeze dried papaya- Freeze dried Banana-
Freeze dried black currants-
Freeze DriedApples-

44. Freeze Dried Blueberries- Freeze Dried Raspberries-
Freeze Dried Carrots-
Freeze Dried Cabbage-

45. Freeze dried Garlic- Freeze Dried Turmeric-
Freeze Dried Red Chilly and Green Chilly-

46. APPLICATIONS OF FREEZE DRYING -
Biggestmarketforfreeze-dryingisthefoodindustry.
Freeze-driedfoodisusedbyhikers,hunters,astronauts,the
military,aswellasbeingusedinthefoodindustryfor
dehydratedsoupsandmealsforconsumersinthe
supermarket.Thelargestapplicationisfreeze-driedcoffee.
freeze-driedmicroorganisms-frequentlyusedfor
fermentationreactions,usedinbioconversionreactionsand
storedforresearch.
Inthepharmaceuticalindustry–Forsaving
manymedicineslivesandforlifesavingsubstancethatis
blood.

47. Freezedriedfruitpowders/slicesdicesareoften
used:
formakingmanydeliciousfoodproductslikeFruit
drinks,icecreams,thickshakes,yogurtandother
dessertswhenfreshfruitsarenotavailable.
usedtomakesoftcandy,toffeeandhardcandy.
makinginstantjuicemixes,flavoringbaby/infant
foods,preparingfoodpremixes,andrangeofbakery
products.
useinrichcreamfillings,chocolateproductsand
bakedgoodsaswellasincerealsandfruitbars.
FREEZEDRIEDFOODPRODUCTAPPLICATIONS-

48. FREEZEDRIEDFOODPRODUCTAPPLICATIONS
Fruitgranulesareusedinproductswherethefruitcontent
desiredalsotextureandcrunchinessisrequired.
Freezedriedspicesandvegetableusedinmanufacturingof
instantvegetablenoodles,soups,snacksanddifferentkindsof
fastfood.
Freezedriedfoodisuseformakingpetfoods.
freeze dried soup

50. ADVANTAGES OF FREEZE DRYING -
1.Retaintaste,smellandtexture–
2.FewerlossofNutrient–
3.Reduceweight–
4.FewerPreservatives–
5.ExtendedShelfLife-
6.TheSafetyAdvantage-
7.RapidRehydrationAdvantage-
Rehydration

51. DISADVANTAGES OF FREEZE DRYING -
1.Expense-
2.Storing-
3.Select Foods-

52. convenientmethodfordryingthosedecomposable
products(mostlypharmaceuticals,e.g.,plasma,vaccines,
antibiotics,sera,andgrowthhormones)thatcannotbe
stabilizedinanyotherwayorthatshowmarkedlyimproved
qualityforaratherhighaveragecost(coffee,mushrooms,
dicedchicken,andothers)
suitableforhigh-valueproductswithspecificbiologicalor
phytochemicalproperties.
CONCLUSION-