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Cold Preservation and Processing

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1920's - Clarence Birdseye initiated frozen food packaging. Storage Temperatures ... Some growth at sub-freezing temps as long as water is available ... – PowerPoint PPT presentation

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Title: Cold Preservation and Processing


1
Cold Preservationand Processing
  • Chapter 9

2
Historical Perspective
  • 1875 - first mechanical ammonia refrigeration
    system invented
  • 1920s - Clarence Birdseye initiated frozen food
    packaging

3
Storage Temperatures
  • Cool storage 16 to -2oC (60 to 28oF)
  • Refrigerators 4.5 to 7oC (40 to 45oF)
  • Frozen storage 0 to -18oC (32 to 0oF)

4
Microbial Growth
  • Best above 10oC (50oF)
  • Some growth at sub-freezing temps as long as
    water is available
  • Little growth below -9.5oC (15 oF)

5
RefrigeratedStorage
6
Cool Storage Is
  • Gentlest method of food preservation
  • Few adverse effects on
  • Taste
  • Texture
  • Nutritive value
  • Color
  • Short time preservation

7
Timeliness of Refrigeration
  • ASAP after harvest/slaughter
  • Remove heat rapidly through use of
  • Moving air
  • Hydrocooling
  • Vacuum cooling
  • Liquid nitrogen

8
Requirement ofRefrigerated Storage
  • Low temperatures
  • Air circulation
  • Humidity control (80 to 95)
  • Modified gas atmospheres

9
Factors AffectingCooling Requirements
  • Cold storage room insulation
  • Frequency of door opening
  • Heat load of food product
  • Quantity of hot product loaded daily
  • Respiration rate of food product
  • C6H12O66O2 Þ 6CO26H2Oheat

10
Controlled Atmosphere Storage
  • Standard cold storage temperatures humidity
  • Reduced O2 levels
  • Elevated CO2 levels
  • Why?

11
C6H12O66O2 Þ6CO26H2Oheat
12
Types of ControlledAtmosphere Storage
  • Drive-in cold storage rooms
  • Packaged
  • Fruits
  • Vegetables
  • Meats
  • Hypobaric (reduced pressure) storage
  • Reduces air (and O2) availability

13
Changes in Food During Refrigerated Storage
  • Chill injury
  • Flavor/odor absorption
  • Loss of
  • Firmness
  • Color
  • Flavor
  • Sugar/acid

14
FrozenStorage
15
Initial Freezing Point
  • Pure water freezes at 0oC (32oF)
  • With dissolved salt, sugar or other components,
    water would freeze at
  • higher temperatures?
  • or
  • lower temperatures?

16
Initial Freezing Point
  • Pure water freezes at 0oC (32oF)
  • With dissolved salt, sugar or other components,
    water would freeze at
  • higher temperatures?
  • or
  • lower temperatures?

17
TRIVIA
  • Why is salt added to ice in a ice cream freezer?
  • How cold is ice when it begins to freeze?
  • How cold will ice get?

18
Freezing Curve
19
Changes During Freezing
  • Concentration effects
  • precipitation, salting-out, dehydration
  • Ice crystal damage
  • cell rupture, emulsion disruption
  • Slow freeze large ice crystals
  • Want a rapid freeze to -18oC (0oF)

20
Intermittent Thawing
  • Increases ice crystal size
  • Damaged cell very susceptible to enzymatic
    degradation

21
Freezing Methods
  • Freezing in air
  • Still-air sharp freezer
  • Blast freezer
  • Fluidized-bed freezer

22
Tunnel Freezer
23
(No Transcript)
24
Freezing Methods
  • Indirect contact freezing
  • Single plate
  • Double plate
  • Pressure plate
  • Slush freezer
  • (In all cases, food or food packages are in
    direct contact with a surface that is cooled by a
    refrigerant)

25
Freezing Methods
  • Immersion freezing
  • Heat exchange fluid
  • Compressed gas
  • Refrigerant spray
  • Very fast freezing using liquid nitrogen
  • IQF Individually Quick Frozen

26
Liquid Nitrogen Spray Freezing Unit
27
Packaging
  • Protect against dehydration
  • Strong flexible
  • Protect against light air
  • Liquid tight
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