Food Preservation, Cold storage and Refrigerators.pdf

Working of Domestic Refrigerators, WATER COOLERS, Methods of food preservations

1. Unit-5:
Food Preservation, Cold Storage,
Refrigerators & Water CoolersRefrigerators & Water Coolers
Prepared by
AnkurSachdeva
Assistant Professor, ME

2. Definition
•FoodPreservationmaybedefinedastheprocess
oftreatingandhandlingfoodinsuchawayasto
stop,control,orgreatlyslowdownspoilageand,
ofcourse,tominimizethepossibilityoffood-
borneillnesswhilemaintainingtheoptimum
nutritionalvalue,texture,andflavor.
borneillnesswhilemaintainingtheoptimum
nutritionalvalue,texture,andflavor.
•Shelf-lifemaybedefinedasthetimeittakesa
producttodeclinetoanunacceptablelevel.
Deteriorationoffoodswillresultinlossofquality
attributes,includingflavor,texture,color,and
othersensoryproperties.
Ankur Sachdeva, Assistant Professor, ME

3. Advantages of Food Preservation
•increased shelf-life
•decreased hazards from microbial pathogen
•decreased spoilage (microbial, enzymatic)
•inactivation of anti-nutritional factors
•ensured round the year availability of seasonal foods
•perishable foods that can be transported to far-off distances from
the site of productionthe site of production
•increased availability of convenience foods (e.g. Ready-to-serve
beverages, Instant mixes etc.)
•increased variety of foods, some with enhanced sensory properties
and nutritional attributes.
•preservation in some cases produces a different form of the
products which are of great importance in various cuisines. E.g.
raisins, squash and wines made from grapes.
Ankur Sachdeva, Assistant Professor, ME

4. Factors Leading to Food Spoilage
•Spoilage due to physical change
–Impact, bruising and squeezing
–desiccation or dehydration•Spoilage due to chemical change•Spoilage due to chemical change
–Internal spoiling agents : Enzymes
–External spoiling agents: bacteria, yeast, moulds
(fungus)
Ankur Sachdeva, Assistant Professor, ME

5. Methods of Food Preservation
•Heat processing
•Dehydration
•Chemical preservation
•Canning •Canning
•Pasteurization
•Freezing
Ankur Sachdeva, Assistant Professor, ME

6. Refrigeration in Food
Preservation
1. Food processing:
(i) Slow freezing
(ii) Quick freezing
-Indirect contact freezing
-Air blast freezers -Air blast freezers
-Immersion freezing
2. Food Preservation:
-Cold storages
3. Distribution:
-Refrigerated vehicles
Ankur Sachdeva, Assistant Professor, ME

7. Shelf Life Vs Temperature..
Ankur Sachdeva, Assistant Professor, ME

8. Recommended Storage Temps.
Product Storage Temperature
Milk 4°C
Butter, Sweets 2°C to 8°C
Ice-Cream -20°C to -22°C
Vegetables 2°C to 8°CVegetables 2°C to 8°C
Fruits 0°C to 4°C
Meat -20°C
Pharma Products 2°C to 8°C
Frozen Fish -18°C to -29°C
Cheese -18°C
Ankur Sachdeva, Assistant Professor, ME

9. Cold Storage
•Coldstorageistheonewidelypracticedmethodforbulk
handlingoftheperishablesbetweenproductionand
marketingprocessing.
•Itisoneofthemethodsofreservingperishable
commoditiesinfreshandwholesomestateforalonger
periodbycontrollingtemperatureandhumiditywithintheperiodbycontrollingtemperatureandhumiditywithinthe
storagesystem.
•Maintainingadequatelylowtemperatureiscritical,as
otherwiseitwillcausechillinginjurytotheproduce.Also,
relativehumidityofthestoreroomshouldbekeptashigh
as80-90%formostoftheperishables,below(or)above
whichhisdetrimentaleffectonthekeepingqualityofthe
product.
Ankur Sachdeva, Assistant Professor, ME

10. Working of Cold Storage plant
•Theworkingprincipleofthecold
storageisbaseduponthevapour
compressionrefrigerationcycle.
•Therefrigerant(ammonia)is
compressedbythecompressor
andisdeliveredtothecondenser
whichiscooledbyafan.
Thehighpressureliquidafter•Thehighpressureliquidafter
beingcooledbyacondenseris
collectedinareceiverfrom
whereitgoestotheexpansion
valve.
•Theexpansionvalvetakesthe
requiredquantityofthe
refrigerantdependinguponthe
loadontheevaporator.
Ankur Sachdeva, Assistant Professor, ME

11. Working of Cold Storage plant
•Evaporator:Itistheheat
exchangerwhereactualcooling
takesplace.Itevaporates
(vaporize)thelow-pressure,low-
temperatureliquidrefrigerant
(withlowboilingpoint)by
taking/utilizingheatfrom
atmosphere/storageatmosphere/storage
compartmenttobecooled,thus
heatcontentoffruitsor
vegetabledecreaseanditcool
duetothiscyclicprocess(Chilled
airisproducedduetoconvection
current)
•Blowers:Itcirculateschilledairin
therefrigeratedspacetocoolthe
fruitsandvegetablesby
convectionprocess.
Ankur Sachdeva, Assistant Professor, ME

12. Benefits of Cold Storage
•Mostfruitsandvegetableshaveaverylimitedlifeafter
harvestifheldatnormalharvestingtemperatures.
Postharvestcoolingrapidlyremovesfieldheat,
allowinglongerstorageperiods.
•Proper postharvest cooling can: •Proper postharvest cooling can:
–Reducerespiratoryactivityanddegradationbyenzymes;
–Reduceinternalwaterlossandwilting;
–Sloworinhibitthegrowthofdecay-producing
microorganisms;
–Reducetheproductionofthenaturalripeningagent,
ethylene.
Ankur Sachdeva, Assistant Professor, ME

13. Types of Cold Storage
•Basedonthepurposethepresentdaycoldstoresareclassifiedinto
followinggroups:
1.Bulkcoldstores:Generally,forstorageofasinglecommodity
whichmostlyoperatesonaseasonalbasisE.g.:storesforpotatoes,
chilies,applesetc.
2.Multipurposecoldstores:Itisdesignedforstorageofvarietyof
commodities,whichoperatepractically,throughouttheyear.commodities,whichoperatepractically,throughouttheyear.
3.Smallcoldstores:Itisdesignedwithprecoolingfacilities.For
freshfruitsandvegetables,mainlyforexportorienteditemslike
grapesetc.
4.Frozenfoodstores:Itisdesignedforwith(or)withoutprocessing
andfreezingfacilitiesforfish,meat,poultry,dairyproductsand
processedfruitsandvegetables.
5.Miniunits/walkincoldstores:Itislocatedatdistributioncenter
etc.
6.Controlledatmosphere(CA)stores:Itismainlydesignedfor
certainfruitsandvegetables
Ankur Sachdeva, Assistant Professor, ME

14. Cold Storage Rooms..
Fruits
Dairy Products
Frozen Fish
Ankur Sachdeva, Assistant Professor, ME

15. Domestic Refrigerator
Ankur Sachdeva, Assistant Professor, ME

16. Internal Parts of a Refrigerator
•Compressor
•Condenser
•Expansion Valve/Capillary
Tube
•Evaporator/Chiller/Freezer•Evaporator/Chiller/Freezer
•Thermostat
•Defrost System
Ankur Sachdeva, Assistant Professor, ME

17. Internal Parts of a Refrigerator
•Compressor:Thecompressorislocatedatthebackof
therefrigeratorandinthebottomarea.The
compressorsuckstherefrigerantfromtheevaporator
anddischargesitathighpressureandtemperature.
Thecompressorisdrivenbytheelectricmotoranditis
themajorpowerconsumingdeviceoftherefrigerator.themajorpowerconsumingdeviceoftherefrigerator.
•Condenser:Thecondenseristhethincoilofcopper
tubinglocatedatthebackoftherefrigerator.The
refrigerantfromthecompressorentersthecondenser
whereitiscooledbytheatmosphericairthuslosing
heatabsorbedbyitintheevaporatorandthe
compressor.Toincreasetheheattransferrateofthe
condenser,itisfinnedexternally.
Ankur Sachdeva, Assistant Professor, ME

18. Internal Parts of a Refrigerator
•Expansionvalve/Capillarytube:Therefrigerantleavingthe
condenserenterstheexpansiondevise,whichisthe
capillarytubeincaseofthedomesticrefrigerators.The
capillaryisthethincoppertubingmadeupofnumberof
turnsofthecoppercoil.Whentherefrigerantispassed
throughthecapillaryitspressureandtemperaturedrops
downsuddenly.downsuddenly.
•Evaporator/Chiller/Freezer:Therefrigerantatverylow
pressureandtemperatureenterstheevaporatororthe
freezer.Theevaporatoristheheatexchangermadeupof
severalturnsofcopperoraluminumtubing.Indomestic
refrigeratorstheplatetypesofevaporatorisusedasshown
inthefigureabove.Therefrigerantabsorbstheheatfrom
thesubstancetobecooledintheevaporator,gets
evaporatedanditthensuckedbythecompressor.This
cyclekeepsonrepeating.
Ankur Sachdeva, Assistant Professor, ME

19. Internal Parts of a Refrigerator
•Temperaturecontroldeviceorthermostat:Tocontrolthe
temperatureinsidetherefrigeratorthereisthethermostat,
whosesensorisconnectedtotheevaporator.The
thermostatsettingcanbedonebytheroundknobinside
therefrigeratorcompartment.Whenthesettemperatureis
reachedinsidetherefrigeratorthethermostatstopsthe
electricsupplytothecompressorandcompressorstops
reachedinsidetherefrigeratorthethermostatstopsthe
electricsupplytothecompressorandcompressorstops
andwhenthetemperaturefallsbelowcertainlevelit
restartsthesupplytothecompressor.
•Defrostsystem:Thedefrostsystemoftherefrigerator
helpsremovingtheexcessicefromthesurfaceofthe
evaporator.Thedefrostsystemcanbeoperatedmanually
bythethermostatbuttonorthereisautomaticsystem
comprisingoftheelectricheaterandthetimer.
Ankur Sachdeva, Assistant Professor, ME

20. External Visible
Parts of a Refrigerator
•Freezer Compartment
•Thermostat Control
•Refrigerator
CompartmentCompartment
•Crisper
•Refrigerator Door
Compartment
•Switch
Ankur Sachdeva, Assistant Professor, ME

21. External Visible
Parts of a Refrigerator
•Freezercompartment:Thefooditemsthataretobe
keptatthefreezingtemperaturearestoredinthe
freezercompartment.Thetemperaturehereisbelow
zerodegreeCelsiussothewaterandmanyotherfluids
freezeinthiscompartment.Ifyouwanttomake
cream,freezethefoodetc.theyhavetobekeptinthecream,freezethefoodetc.theyhavetobekeptinthe
freezercompartment.
•Thermostatcontrol:Thethermostatcontrolcomprises
oftheroundknobwiththetemperaturescalethathelp
settingtherequiredtemperatureinsidethe
refrigerator.Propersettingofthethermostatasperthe
requirementscanhelpsavinglotsofrefrigerator
electricitybills
Ankur Sachdeva, Assistant Professor, ME

22. External Visible
Parts of a Refrigerator
•Refrigeratorcompartment:Therefrigerator
compartmentisthebiggestpartoftherefrigerator.
Hereallthefooditemsthataretobemaintainedat
temperatureabovezerodegreeCelsiusbutincooled
conditionarekept.Therefrigeratorcompartmentcanconditionarekept.Therefrigeratorcompartmentcan
bedividedintonumberofsmallershelveslikemeat
keeper,andothersaspertherequirement.
•Crisper:Thehighesttemperatureintherefrigerator
compartmentismaintainedinthecrisper.Hereone
cankeepthefooditemsthatcanremainfreshevenat
themediumtemperaturelikefruits,vegetables,etc.
Ankur Sachdeva, Assistant Professor, ME

23. External Visible Parts of a
Refrigerator (Contd..)
•Refrigeratordoorcompartment:Thereare
numberofsmallersubsectionsintherefrigerator
maindoorcompartment.Someoftheseareegg
compartment,butter,dairy,etc.
•Switch:Thisisthesmallbuttonthatoperatesthe•Switch:Thisisthesmallbuttonthatoperatesthe
smalllightinsidetherefrigerator.Assoonthe
dooroftherefrigeratoropens,thisswitch
supplieselectricitytothebulbanditstarts,while
whenthedoorisclosedthelightfromthebulb
stops.Thishelpsinstartingtheinternalbulbonly
whenrequired.
Ankur Sachdeva, Assistant Professor, ME

24. Working of Domestic Refrigerator
Ankur Sachdeva, Assistant Professor, ME

25. Water Coolers
Parts of a Water Cooler:
1. Compressor
2. Motor
3. Receiver
4. Condenser4. Condenser
5. Expansion Valve
6. Evaporating coils
surrounding water tank
7. Water Tank
8. Cover
9 & 10. Pressure gauges
Ankur Sachdeva, Assistant Professor, ME

26. Working of Water Cooler
•Theworkingprincipleofthe
watercoolerisbaseduponthe
vapourcompressionrefrigeration
cycle.
•Therefrigerantiscompressedby
thecompressorandisdelivered
tothecondenserwhichiscooled
byafan.byafan.
•Thehighpressureliquidafter
beingcooledbyacondenseris
collectedinareceiverfrom
whereitgoestotheexpansion
valve.
•Theexpansionvalvetakesthe
requiredquantityofthe
refrigerantdependinguponthe
loadontheevaporator.
Ankur Sachdeva, Assistant Professor, ME

27. Working of Water Cooler
•Astherefrigerantpassedthroughthe
expansionvalve,itstemperaturefalls
downconsiderably(upto–10°C).Its
pressurealsofallsdown.
•Thenthisliquidrefrigerantpasses
throughtheevaporatorcoils,which
surroundthewatertank(watermay
bestoredinit).Theliquidrefrigerant
inthecoilsabsorbsitslatentheat
bestoredinit).Theliquidrefrigerant
inthecoilsabsorbsitslatentheat
fromthewater,leavingitcooled.
•Theliquidrefrigerantasitflows
throughtheevaporatorcoilsis
convertedintovapourandbythe
timeitleavesthecoils,itisalmost
convertedintodryvapour.This
vapourisagaincompressedthrough
thecompressor.
•Thiswaythiscycleisrepeatedagain
andagain.Thecooledwatermaybe
drainedoutandthefreshwatermay
beaddedtothetankforcooling
Ankur Sachdeva, Assistant Professor, ME