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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
Pressure when using vacuum cooler
0.5 kPa
26
Two ways of freezing fruits
1. Sugar pack 2. Syrup pack
27
Raw materials are cooked under controlled conditions of temp and time inside heat-stable vacuumized pouches
Sous vide
28
How are vegetables hydro cooled in wet markets in the philippines
Spraying with cold water (household method)
29
Deteriorative chemical reactions
- chemical changes associated with color degradation - autolysis of fish - loss of nutritive value of foods in general
30
4 types of cooled air freezers
Chest freezers Blast freezers Belt freezers Fluidized bed freezers
31
Main Goal of Preservation
prevent microoranism from growing
32
T or F: Microorganisms still grow at 15 C
True but activity is only slowed down
33
Why are tomatoes injured when refrigerated
Carotenoids are not fully developed
34
How do hydro coolers work
Produce on conveyor belt and showered with cold water
35
Blast freezers utilizes _____ which are slower than ______.
-fast freezing -plate freezer
36
T or F: Potharvest metabolic activities are still present during refrigeration
True but activities are only slowed down
37
Problems in Blast freezers
-Moisture loss -High capital cost
38
What do wrinkles in food indicate
Moisture loss
39
Causes shrunk cells and destructed tissue, not good for industry use.
Slow Freezing
40
What happens in large ice crystal damage and recrystallization?
-Physical rupture of cell walls and membranes & separation of plant & animal cells -Disruption of emulsion, foams, and gels
41
Means under vacuum
Sous vide
42
Chest freezers is used as
storage after freezing
43
Maximum chilling storage time and temp in sous vide
Up to 21 days, 0-3 C
44
The ______ component of a food freezes first and leaves the _____ in a more concentrated solution, which requires a ________to freeze.
-water -dissolved solids -lower temperature
45
Optimum temperature of eggplant
10 C
46
Air conditions in blast freezers
-400m/min→ rapid heat transfer -Temperature: -25 to -36°C
47
What are the 2 principles of freezing food?
-Lowering of temperature by removal of heat in food -change of phase from liquid to solid (water to ice)
48
__________ pattern of thawing potentially more detrimental than freezing.
Time-temperature
49
Keri pa ba mag review sis? :((
Wala kang choice :)
50
_______ during thawing is less than in freezing.
Temperature differential
51
T or F In order for a product to freeze, the product must be cooled above its freezing point.
F. Above -> Below
52
What is an ice box
Closed, wooden box that contained a block of ice in a chamber above the food to keep it cold
53
Cold storage facility provides __- __ yrs shelf life
2-3 yrs
54
T or F: fruits and vegetables have optimum storage temperature like microbes
True
55
Cold loving microorganisms that will eventually spoil food
Psychrophile
56
added in storing food items to occupy headspace and prevent freezer burn
Parchment paper or plastic (cling wrap) or Freezer wrap
57
Optimum temperature of eggplant
10 C
58
2 Quality changes in Fast Freezing
-Freeze concentration effect -Large ice crystal damage and recrystallization
59
Difference between Chest Freezer and Blast Freezers
Chest freezer uses still air, Blast freezer has super cooled air
60
T or F: Foods will never spoil under refrigeration
False, just a slower process
61
Do you think refreezing is encouraged? Yes or No? ^____^
NOOOOOOO!!!! >:(( As much as possible, do not refreeze
62
Tips in preventing freezer burn
-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
What results after production of gases, slime, pigments and enzymes
- Softening - rotting - off-flavors and odors - breakdown of food components
64
Cold Storage System includes (VIDEO)
Cold storage facility Blast freezer facility Individually Quick Freezing (IQF) facility
65
Results to less damaged tissue with maintained integrity, good for industry use.
Fast freezing
66
Dangers of sous vide
- 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
Difference of traditional cooking and sous vide
Traditional: cooked directly in a pot Sous vide: packed and cooked using precisely controlled heating
68
Main considerations in thawing
-avoid overheating -minimize thawing times -avoid excessive dehydration of the food
69
Purpose of rapid chilling in sous vide
To stop the cooking process
70
What was the means of cold preservation in the middle 1800s
Ice
71
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.
T
72
______ must not suffer in refreezing because it is ______.
-Quality -product dependent
73
What type of container used in sous vide
Laminated plastic pouch or container
74
T or F Foods have different freezing point.
T
75
In what type of food service is cook-chill process is applied
Quick-service restaurants and Commissary food service
76
Air speed and temperature of blast chiller
4 m/s and 4 C
77
Why is refrigeration good for preventing microorganism growth but unacceptable for food quality?
Microorganism growth: moisture loss Food Quality: dries out produce
78
Injury in frozen food which occurs when there is a headspace in the packaged food and the food is subjected to fluctuating storage temperatures
Freezer Burn
79
T or F Thawing is generally faster than freezing.
F. Faster -> slower
80
Operate by passing cold air over foodstuffs at high speed
Blast chiller
81
What type of environment is naturally cold
Environment with rocks
82
Minimum recommended thermal process for sous vide
90 C for 10 min or it's t-T equivalent (combination of time and temperature)
83
Types of Blast Freezer
-Spiral -Cabinet -Belt
84
How to prevent moisture loss
Wrap the food
85
Process of sous vide
1. Raw or parcooked food 2. Vacuum sealing 3. Heat treatment 4. Rapid chilling 5. Reheated for service
86
Benefits of vacuum sealing
- 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
What happens to mangoes under refrigeration
Skin defects due to abnormal continuation of physiological growth
88
what causes moisture loss in the refrigerator
relative humidity
89
T or F: Using hydro coolers has the risk of freezing
False

FN 132 - LE #2 (8 decks)

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