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Food Chemistry 2 > Ppt 3 > Flashcards

Ppt 3 Flashcards

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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
Q

What oxidoreductase enzyme is heat stable?

A

Peroxidase

26
Q

What should the peroxidase activity be in sterilized broccoli compared to normal? What would it mean if the peroxidase levels were the same?

A
  • low because high heat used for long time

- most likely used sterilization or blanching, not high heat treatment

27
Q

Peroxidase is used as an index for what?

A

High heat treatment

28
Q

What reaction does glucose oxidase catalyze?

A

glucose + O2 –> gluconic acid + H2O2

29
Q

What are3 results in foods after the application of glucose oxidase?

A
  1. de-sugaring
  2. pH decrease
  3. O2 removal (reduce oxidation)
30
Q

What oxidoreductase enzyme is very heat sensitive?

A

ascorbic acid oxidase

31
Q

What reaction does ascorbic acid oxidase catalyze?

A

Ascorbic acid + O2 –> dehydroascrobic acid + O2

32
Q

What is ascorbic acid?

A

Vitamin C

33
Q

Are proteases highly specific?

A

Yes

34
Q

What are the 2 major COHs found in foods?

A

starch and cellulose

35
Q

Out of starch & cellulose, which one is much more resistant to enzymatic hydrolysis?

A

Cellulose

36
Q

What 2 enzymes hydrolyze starch?

A
  1. Amylase

2. Glucoamylase

37
Q

What enzyme hydrolyses cellulose?

A

Cellulase

38
Q

What are 4 traditional methods for controlling enzymatic reactions in foods based on Temperature?

A

blanching, freezing, chilling, pasteurization

39
Q

What are 2 traditional methods for controlling enzymatic reactions in foods based on Aw?

A

salting, dehydration

40
Q

What are 4 traditional methods for controlling enzymatic reactions in foods based on Chemicals?

A

sulfites, acids, alkalis, antioxidants, chelating agents

41
Q

What is a novel method for controlling enzymatic reactions in foods based on high pressure treatment?

A

ultra high pressure processing

42
Q

What is a novel method for controlling enzymatic reactions in foods based on enzyme treatment?

A

killer enzymes/anti-enzyme enzymes

43
Q

What are 3 other types of novel methods for controlling enzymatic reactions in foods?

A

Enzyme inhibitors, Microwave, Ultrasonic

+ High pressure treatment, Enzyme treatment

Food Chemistry 2 (6 decks)

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