8. Flavor/Quality evaluation of fats/oils

Question 1

How to do flavor quality evaluation? (4 ways)

Answer 1

1. sensory evaluation
2. peroxide value
3. thiobarbituric acid test
4. gas chromatographic analysis of volatile compounds

Question 2

2 things needed for sensory eval?

Answer 2

• trained people
• controlled temp and environment

Question 3

Peroxide value:
- addition of ____A______ and _______B______ in an organic solvent to oil
1) A + B –> salt + _C__
2) ROOH + 2 C –> ____ + _____ + __D___
3) D (what color) + ____________ –> ____ + 2 _____ (color?)

Answer 3

A: potassium iodine
B: acetic acid
C: hydroiodic acid
ROOH + 2 HI –> ROH + I2 + H2O
I2 (purple) + sodium thiosulfate –> Na2S4O6 + 2 NaI (no color)

Question 4

what color is the we react TBA and malondialdehyde?

Answer 4

red!

Question 5

what is gas chromatographic analysis of volatile compounds?

Answer 5

gas syringe sucks gas from oil –> gas is put through gas chromatography –> generates figure with peaks!

Question 6

increase hours of light exposure = increase/decrease size of 2,4 decadienals in GC?

Answer 6

increase!

Question 7

Does soybean or corn oil have faster degradation?

Answer 7

soybean bc more omega 3!

Question 8

Flavor stability measurement: what is active oxygen method?
- more O2 sample takes = more _________ it makes –> measure weight!

Answer 8

O2 passing at controlled rate at 98°C into sample at 2.33 mL/sec until it becomes rancid
- more hydroperoxide it makes

Question 9

what is deep fat frying?

Answer 9

process of immersing food in hot oil

Question 10

Deep fat frying:
- combination of cooking and dehydrating of food produces unique fried foods by simultaneous ______ and _______ transfer
- flavor compounds are formed and retained in a ____________ on the food

Answer 10

• heat and mass
• crips crust

Question 11

4 physical changes of oil during deep-fat frying

Answer 11

• thickening of oil (increase in viscosity)
• decrease of interfacial tension
• increase in density
• increase of specific heat

Question 12

4 chemical changes during deep fat frying

Answer 12

• formation of flavor
• flavor stability and quality changes
• changes in color and texture of fried foods
• nutritional changes

Question 13

4 chemical reactions in frying oil

Answer 13

• hydrolysis of TG
• oxidation
• polymerization (FR from oxidation)
• pyrolysis

Question 14

2 noteworthy compounds formed in deep fat frying conditions

Answer 14

• hexyl benzene
• 2,4 decadienal

Question 15

high temp in deep fat frying can also cause _____________

Answer 15

isomerization!

Question 16

sticky stuff on your pan after frying = _____________
- btw what?

Answer 16

• dimerization
• 2 acyl groups of same TG or of 2 dif TG