L17 - Meat Freezing

Question 1

Benefits of freezing meat

Answer 1

prolongs the shelf-life and maintains acceptable quality of meats for months and even years

Question 2

At temperature below _____C, most deterioration due to ___________ is curtailed

Answer 2

below -18C, microbial and enzymatic activity is curtailed

Question 3

The optimum temperature for the frozen storage of meat is _____C

Answer 3

-40C

Question 4

Even at optimum temperature, there is still a small fraction of water unfrozen, what is this water?

Answer 4

bound water

Question 5

Primary vs Secondary lipid oxidation

Answer 5

Primary lipid oxidation: chemical reactions that occur during frozen storage

Secondary lipid oxidation: radical lipid oxidation that occur when thawed (changes color, odor, flavor, and healthfulness)

Question 6

Three periods of the freezing process

Answer 6

1. Pre-cooling or chilling
2. Phase change/transition
3. Sub-cooling or tempering

Question 7

Pre-cooling Phase

Answer 7

1. sensible heat is removed
2. ends right before crystallization

Question 8

Phase-change Phase

Answer 8

1. removes latent heat
2. myowater starts to crystallize

Question 9

Tc

Answer 9

amount of time taken to pass critical freezing point
(faster is better)

Question 10

Sub-cooling Phase

Answer 10

1. after most of the freezable water is converted to ice

Question 11

How do ice crystals grow larger?

Answer 11

difference in vapor pressure causes intracellular water to move and deposit on extracellular ice crystals

Question 12

Effects of ice crystals

Answer 12

1. Dehydrates the cells (looks shrunken)
2. Deform/rupture cells (if crystal large enough)
3. Cause drip loss when thawed

Question 13

What effects shelf life of frozen meat?

Answer 13

1. Packaging/wrapping condition
2. Freezing temperature (freezing rate)
3. Constant storage temperature

Question 14

Freezer burn

Answer 14

myowater undergoes sublimation which leads to surface dehydration

1. lipid oxidation
2. protein denaturation
3. reduced juiciness
4. reduced tenderness
5. off-flavor
6. corklike texture
7. gray to tan color

Question 15

Does freezing kill microbes?

Answer 15

No, it just makes them dormant so spoilage cannot occur

Question 16

Why does defrosted meat spoil faster?

Answer 16

because of damage to tissue and exudate which enhances microbial growth

Question 17

Bacterial/fungal _____ and ______ are highly resistant to freezing

Answer 17

spores and toxins

Question 18

Slow freezing rate

Answer 18

1. frozen front moves 0.1-0.2 cm/hr
2. large extracellular ice crystals form
3. damage muscle protein and cell membranes
4. purge upon thawing

Question 19

Intermediate freezing rate

Answer 19

1. frozen front moves 0.2-1.0 cm/hr
2. medium ice crystals (intra/extra)
3. damage muscle protein and cell membrane
4. purge upon thawing

Question 20

Fast freezing rate

Answer 20

1. frozen front moves at 1.0-10.0 cm/hr
2. Small intracellular ice crystals
3. uniformly distributed
4. minimal damage

Question 21

Ultra-fast freezing rate

Answer 21

1. frozen front moves 10+ cm/hr
2. may cause freeze-cracking

Question 22

Freezing methods

Answer 22

1. Still air
2. Plate freezing
3. Blast freezing
4. Liquid immersion and liquid sprays
5. Cryogenic freezing

Question 23

Worst combination of freezing/thawing rates?

Answer 23

Slow freezing with fast thawing