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Ppt 3 Flashcards

1
Q

What enzyme causes browning?

A

PPO - Polyphenol Oxidase

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2
Q

What compound gives the brown color after enzymatic browning?

A

Melanin

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3
Q

Show enzymatic browning equation

A

-

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4
Q

What are 2 undesirable effects caused by enzymes in food?

A

Browning & Spoilage

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5
Q

What is spoilage

A

Texture, flavour, and safety change

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6
Q

What are 5 examples of enzymes that cause spoilage?

A
  1. Pectinase + glycosidase
  2. Lipoxygenase (lox)
  3. Protease
  4. Lipase
  5. Histadine Decarboxylase
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7
Q

Ex. of a reaction that Lipoxigenase catalyses?

A

Unsaturated fatty acids + O2 –(lox)–> fatty acid hydroperoxidase

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8
Q

What do Pectinase + glycosidase catalyze? What structure does this produce?

A

hydrolyze the pectin and starch – soft texture

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9
Q

What does Lipoxigenase cause? Example

A

causes oxidized odor in food “beany flavour in beans”

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10
Q

What do proteases form?

A

bitter peptides in protein foods

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11
Q

What process can be used to “de-bitter” foods affected by protease?

A

intensive hydrolysis

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12
Q

What does histidine decarboxylase catalyze?

A

Histidine –> histamine + CO2 - TOXIC/SAFETY ISSUE

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13
Q

PPO gives brown color to what 2 drinks?

A

coffee, black tea

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14
Q

What 3 enzymes affect flavour?

A

LOX, Lipases, Proteases

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15
Q

What enzyme affects color?

A

PPO

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16
Q

What are 3 sources of industrial enzymes? What % do they make up?

A
  1. Microorganisms (80-90%)
  2. Animal (6-8%)
  3. Plant (3-5%)
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17
Q

What 2 enzymes are used to make cheese?

A
  1. Rennet

2. Pepsin

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18
Q

What does rennet contain?

A

chymosin/rennin

19
Q

What enzymes are used in winemaking & brewing?

A

proteases, amylases

20
Q

What enzymes are used in baking?

A

amylases, proteases, lipoxigenases

21
Q

In the meat industry, what enzymes are used for tenderization and solubilization?

A

Proteases: papain & bromelain

22
Q

In the meat industry, what enzymes are used for texturization?

A

transglutaminase - firm texture

23
Q

What enzyme does high fructose corn syrup use?

A

glucose isomerase

24
Q

What are 5 important oxidoreductases in food processing?

A
  1. polyphenol oxidase
  2. peroxidase
  3. lipoxygenase
  4. glucose oxidase
  5. ascorbic acid oxidase
25
What oxidoreductase enzyme is heat stable?
Peroxidase
26
What should the peroxidase activity be in sterilized broccoli compared to normal? What would it mean if the peroxidase levels were the same?
- low because high heat used for long time | - most likely used sterilization or blanching, not high heat treatment
27
Peroxidase is used as an index for what?
High heat treatment
28
What reaction does glucose oxidase catalyze?
glucose + O2 --> gluconic acid + H2O2
29
What are3 results in foods after the application of glucose oxidase?
1. de-sugaring 2. pH decrease 3. O2 removal (reduce oxidation)
30
What oxidoreductase enzyme is very heat sensitive?
ascorbic acid oxidase
31
What reaction does ascorbic acid oxidase catalyze?
Ascorbic acid + O2 --> dehydroascrobic acid + O2
32
What is ascorbic acid?
Vitamin C
33
Are proteases highly specific?
Yes
34
What are the 2 major COHs found in foods?
starch and cellulose
35
Out of starch & cellulose, which one is much more resistant to enzymatic hydrolysis?
Cellulose
36
What 2 enzymes hydrolyze starch?
1. Amylase | 2. Glucoamylase
37
What enzyme hydrolyses cellulose?
Cellulase
38
What are 4 traditional methods for controlling enzymatic reactions in foods based on Temperature?
blanching, freezing, chilling, pasteurization
39
What are 2 traditional methods for controlling enzymatic reactions in foods based on Aw?
salting, dehydration
40
What are 4 traditional methods for controlling enzymatic reactions in foods based on Chemicals?
sulfites, acids, alkalis, antioxidants, chelating agents
41
What is a novel method for controlling enzymatic reactions in foods based on high pressure treatment?
ultra high pressure processing
42
What is a novel method for controlling enzymatic reactions in foods based on enzyme treatment?
killer enzymes/anti-enzyme enzymes
43
What are 3 other types of novel methods for controlling enzymatic reactions in foods?
Enzyme inhibitors, Microwave, Ultrasonic | + High pressure treatment, Enzyme treatment

Food Chemistry 2 (6 decks)

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