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FN 132 - LE #2 > Low Temp Preservation > Flashcards

Low Temp Preservation Flashcards

1
Q

T or F

Poor maintenance and equipment care of freezers lead to formation of small ice crystals

A

F.

Small -> large ice crystals

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2
Q

How do people used to store food?

A
  • In cold cellars
  • holes in the ground
  • Natural Caves
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3
Q

Post____ metabolic activities of intact plant tissues and post____ metabolic activities of animal tissues

A

plant: postharvest
animal: post slaughter

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4
Q

What happens in Freeze concentration effect?

A

-Loss of consistency
-syneresis
-chemical reaction

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5
Q

T or F: fungicide is used in hydro coolers

A

True but sometimes only

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6
Q

When was mechanical refrigeration introduced

A

Later 1800s

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7
Q

Major disadvantage of chest freezer

A

Slow freezing

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8
Q

Cook-chill process

A
  1. Cook
  2. Chill
  3. Store
  4. Regeneration & service
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9
Q

Produces small crystals, necessary for high quality products such as ice cream

A

Fast freezing

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10
Q

Applied mainly for prepacked vegetables with large surface area

A

Vacuum coolers

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11
Q

Chest freezers are relatively ____, ____, and _____.

A

Simple, versatile, cheap

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12
Q

Why is chilling vital in sous vide

A

Induce thermal shock to microorganism

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13
Q

T or F

Refreezing is microbiologically okay if temperature is high.

A

F. High -> Low

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14
Q

Requirements for growth of microorganism

A
  • prefer water
  • cannot tolerate high sugar/salt
  • cannot tolerate alcohol
  • optimum temperature
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15
Q

Use of chill water, either by spraying or immersion

A

Hydro coolers

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16
Q

On what food is hydro cooler used

A

Produce with thick skin so water cannot penetrate

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17
Q

Types of Chest freezers and difference between the two

A

Chest Freezer retain cold air
Cabinet System lose cold air when door is opened

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18
Q

T or F

Blast Freezing facility can freeze food items within 30 minutes.

A

F. Blast Freezing -> Individually Quick Freezing (IQF)

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19
Q

Freezing is the unit operation in which the temperature of a food is reduced below the __________ and a proportion of the water undergoes a _________ to form ______.

A

-freezing point
-phase change
-ice

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20
Q

T or F

Thawing is usually less controlled than freezing (or accidental).

A

True

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21
Q

Chilling temperature

A

Above freezing and below 15 C

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22
Q

Steps in Refreezing

A

-remanufacture
-cook and refreeze
-test for microorganisms if not sure

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23
Q

Application of heat until the ice present has reverted to water

A

Thawing

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24
Q

True or False

Thawing could be more damaging than freezing

A

True

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25
Q

Pressure when using vacuum cooler

A

0.5 kPa

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26
Q

Two ways of freezing fruits

A
  1. Sugar pack
  2. Syrup pack
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27
Q

Raw materials are cooked under controlled conditions of temp and time inside heat-stable vacuumized pouches

A

Sous vide

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28
Q

How are vegetables hydro cooled in wet markets in the philippines

A

Spraying with cold water (household method)

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29
Q

Deteriorative chemical reactions

A
  • chemical changes associated with color degradation
  • autolysis of fish
  • loss of nutritive value of foods in general
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30
Q

4 types of cooled air freezers

A

Chest freezers
Blast freezers
Belt freezers
Fluidized bed freezers

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31
Q

Main Goal of Preservation

A

prevent microoranism from growing

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32
Q

T or F: Microorganisms still grow at 15 C

A

True but activity is only slowed down

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33
Q

Why are tomatoes injured when refrigerated

A

Carotenoids are not fully developed

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34
Q

How do hydro coolers work

A

Produce on conveyor belt and showered with cold water

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35
Q

Blast freezers utilizes _____ which are slower than ______.

A

-fast freezing
-plate freezer

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36
Q

T or F: Potharvest metabolic activities are still present during refrigeration

A

True but activities are only slowed down

37
Q

Problems in Blast freezers

A

-Moisture loss
-High capital cost

38
Q

What do wrinkles in food indicate

A

Moisture loss

39
Q

Causes shrunk cells and destructed tissue, not good for industry use.

A

Slow Freezing

40
Q

What happens in large ice crystal damage and recrystallization?

A

-Physical rupture of cell walls and membranes & separation of plant & animal cells

-Disruption of emulsion, foams, and gels

41
Q

Means under vacuum

A

Sous vide

42
Q

Chest freezers is used as

A

storage after freezing

43
Q

Maximum chilling storage time and temp in sous vide

A

Up to 21 days, 0-3 C

44
Q

The ______ component of a food freezes first and leaves the _____ in a more concentrated solution, which requires a ________to freeze.

A

-water
-dissolved solids
-lower temperature

45
Q

Optimum temperature of eggplant

A

10 C

46
Q

Air conditions in blast freezers

A

-400m/min→ rapid heat transfer
-Temperature: -25 to -36°C

47
Q

What are the 2 principles of freezing food?

A

-Lowering of temperature by removal of heat in food
-change of phase from liquid to solid (water to ice)

48
Q

__________ pattern of thawing potentially more detrimental than freezing.

A

Time-temperature

49
Q

Keri pa ba mag review sis? :((

A

Wala kang choice :)

50
Q

_______ during thawing is less than in freezing.

A

Temperature differential

51
Q

T or F

In order for a product to freeze, the product must be cooled above its freezing point.

A

F. Above -> Below

52
Q

What is an ice box

A

Closed, wooden box that contained a block of ice in a chamber above the food to keep it cold

53
Q

Cold storage facility provides __- __ yrs shelf life

A

2-3 yrs

54
Q

T or F: fruits and vegetables have optimum storage temperature like microbes

A

True

55
Q

Cold loving microorganisms that will eventually spoil food

A

Psychrophile

56
Q

added in storing food items to occupy headspace and prevent freezer burn

A

Parchment paper or plastic (cling wrap) or Freezer wrap

57
Q

Optimum temperature of eggplant

A

10 C

58
Q

2 Quality changes in Fast Freezing

A

-Freeze concentration effect
-Large ice crystal damage and recrystallization

59
Q

Difference between Chest Freezer and Blast Freezers

A

Chest freezer uses still air, Blast freezer has super cooled air

60
Q

T or F: Foods will never spoil under refrigeration

A

False, just a slower process

61
Q

Do you think refreezing is encouraged? Yes or No? ^____^

A

NOOOOOOO!!!! >:((

As much as possible, do not refreeze

62
Q

Tips in preventing freezer burn

A

-Remove headspace in food packages through vacuum pack
-Repackage food items in plastic bas and remove air before storing
-Put plastic wrap/freezer wrap/parchment paper with food items inside the container to prevent moisture vapor

63
Q

What results after production of gases, slime, pigments and enzymes

A
  • Softening
  • rotting
  • off-flavors and odors
  • breakdown of food components
64
Q

Cold Storage System includes (VIDEO)

A

Cold storage facility
Blast freezer facility
Individually Quick Freezing (IQF) facility

65
Q

Results to less damaged tissue with maintained integrity, good for industry use.

A

Fast freezing

66
Q

Dangers of sous vide

A
  • Pasteurizing does not reduce pathogenic spores to a safe level
  • foods which are safe for sous vide are limited
  • if not chilled rapidly enough or refrigerated too long, pathogenic spores can outgrow and multiply to dangerous levels
67
Q

Difference of traditional cooking and sous vide

A

Traditional: cooked directly in a pot
Sous vide: packed and cooked using precisely controlled heating

68
Q

Main considerations in thawing

A

-avoid overheating
-minimize thawing times
-avoid excessive dehydration of the food

69
Q

Purpose of rapid chilling in sous vide

A

To stop the cooking process

70
Q

What was the means of cold preservation in the middle 1800s

A

Ice

71
Q

T or F

Change of water into ice will result in the increase of concentration of unfrozen matrix, leading to dehydration and lowering of water activity.

A

T

72
Q

______ must not suffer in refreezing because it is ______.

A

-Quality
-product dependent

73
Q

What type of container used in sous vide

A

Laminated plastic pouch or container

74
Q

T or F

Foods have different freezing point.

A

T

75
Q

In what type of food service is cook-chill process is applied

A

Quick-service restaurants and Commissary food service

76
Q

Air speed and temperature of blast chiller

A

4 m/s and 4 C

77
Q

Why is refrigeration good for preventing microorganism growth but unacceptable for food quality?

A

Microorganism growth: moisture loss
Food Quality: dries out produce

78
Q

Injury in frozen food which occurs when there is a headspace in the packaged food and the food is subjected to fluctuating storage temperatures

A

Freezer Burn

79
Q

T or F

Thawing is generally faster than freezing.

A

F. Faster -> slower

80
Q

Operate by passing cold air over foodstuffs at high speed

A

Blast chiller

81
Q

What type of environment is naturally cold

A

Environment with rocks

82
Q

Minimum recommended thermal process for sous vide

A

90 C for 10 min or it’s t-T equivalent (combination of time and temperature)

83
Q

Types of Blast Freezer

A

-Spiral
-Cabinet
-Belt

84
Q

How to prevent moisture loss

A

Wrap the food

85
Q

Process of sous vide

A
  1. Raw or parcooked food
  2. Vacuum sealing
  3. Heat treatment
  4. Rapid chilling
  5. Reheated for service
86
Q

Benefits of vacuum sealing

A
  • Inhibits off flavors from oxidation
  • prevents evaporative losses of flavor volatiles and moisture
  • reduce aerobic bacterial growth (results in especially flavorful and nutritious food)
87
Q

What happens to mangoes under refrigeration

A

Skin defects due to abnormal continuation of physiological growth

88
Q

what causes moisture loss in the refrigerator

A

relative humidity

89
Q

T or F: Using hydro coolers has the risk of freezing

A

False

FN 132 - LE #2 (8 decks)

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