Frozen food quality + stability

Question 1

What causes quality loss in frozen food during storage? (5)

Answer 1

enzyme/chem rxn still continue, but slower
ice crystals -> texture damage
moisture loss
pH change
protein instability

Question 2

The main problem with frozen food is: ____ due to _____

How can we prevent this?

Answer 2

physical defects: loss of texture; due to drip loss or freezer burn

fast freezing rate (smaller ice crystals)
stable storage temp (otherwise will melt/recrystallize)
glaze to prevent freezer burn

Question 3

What are the various storage temperatures for frozen food?

Answer 3

common: -18C
long term: -30 to -40C
retail/display: -10C
home: -5 to -10C

Question 4

How does frozen storage help preserve high quality? (3)

Answer 4

Aw almost zero
greatly reduce chem and enzyme rxn
no growth of pathogen/spoilage microbes

Question 5

How can enzymatic and chemical reactions be limited? (9)

Answer 5

low temp
antioxidants
chelators
blanching (inactivate enzymes)
vacuum package (fatty foods - prevent oxidation)
gas flush with N2 or CO2 - eliminate O2
barrier package
immerse in sugar
preservatives (SO2, ascorbic/citric/sorbic acid, benzoates, K metabisulfite)

Question 6

What is the “TTT?” What does it describe?

Answer 6

time-temperature-tolerance (establish by west regional research lab of USDA)

LONGER time -> lower quality
storage life prolonged by lower temp

Question 7

As storage temperature increases, storage life will ___.

As time increases, quality will ____.

Answer 7

decrease logarithmically; decrease

Question 8

What products have the shortest storage life at -18C?

Answer 8

pork brain/liver, deli meats, precooked bacon, ham, sausage
sponge cakes, spice cakes
(last 3 months)

Question 9

The 2 concepts of storage life:

Answer 9

1. PSL - practical storage life: max storage time that gives ACCEPTABLE product
2. HQL - high quality life - storage time that product cannot be JUST differentiated from control (product frozen at very low temp)

Question 10

The PSL is established by:

Answer 10

marketing people, based on consumer input

Question 11

How is HQL established?

Answer 11

determined under controlled conditions:
tasting panel use triangle test
frozen food is distinguished from frozen food at -40C or lower by 75% of panelists

Question 12

Why might PSL for the same product and conditions be variable?

Answer 12

depends on demographic consumer preferences

Question 13

What is the triangle test?

Answer 13

presented with 3 samples, need to identify odd one out (could be 2 control, 1 sample; or 2 sample, 1 control)

Question 14

What is higher, PSL or HQL?

Answer 14

PSL usually 2-6x higher

Question 15

PSL and HQL both also show a ____ relationship with time

Answer 15

semilog inverse

Question 16

What is the z value?

Answer 16

temp increase that will decrease HQL or PSL by 1 log cycle

Question 17

What is the concept of “residual HQL?”

Answer 17

quality deterioration continues at every stage of storage, cannot regain quality
important to determine how much of the HQL time is left when purchased by consumer - determines how long consumer can store

Question 18

Why does the residual HQL need to be calculated?

Answer 18

various stages of storage at different temp, different fractions of HQL lost at each stage
determine each loss -> find how much of HQL is left

Question 19

What is the cold chain the product moves through?

Answer 19

manufacturing -> distribution -> retail -> consumer