Ppt 3 Flashcards
What enzyme causes browning?
PPO - Polyphenol Oxidase
What compound gives the brown color after enzymatic browning?
Melanin
Show enzymatic browning equation
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What are 2 undesirable effects caused by enzymes in food?
Browning & Spoilage
What is spoilage
Texture, flavour, and safety change
What are 5 examples of enzymes that cause spoilage?
- Pectinase + glycosidase
- Lipoxygenase (lox)
- Protease
- Lipase
- Histadine Decarboxylase
Ex. of a reaction that Lipoxigenase catalyses?
Unsaturated fatty acids + O2 –(lox)–> fatty acid hydroperoxidase
What do Pectinase + glycosidase catalyze? What structure does this produce?
hydrolyze the pectin and starch – soft texture
What does Lipoxigenase cause? Example
causes oxidized odor in food “beany flavour in beans”
What do proteases form?
bitter peptides in protein foods
What process can be used to “de-bitter” foods affected by protease?
intensive hydrolysis
What does histidine decarboxylase catalyze?
Histidine –> histamine + CO2 - TOXIC/SAFETY ISSUE
PPO gives brown color to what 2 drinks?
coffee, black tea
What 3 enzymes affect flavour?
LOX, Lipases, Proteases
What enzyme affects color?
PPO
What are 3 sources of industrial enzymes? What % do they make up?
- Microorganisms (80-90%)
- Animal (6-8%)
- Plant (3-5%)
What 2 enzymes are used to make cheese?
- Rennet
2. Pepsin
What does rennet contain?
chymosin/rennin
What enzymes are used in winemaking & brewing?
proteases, amylases
What enzymes are used in baking?
amylases, proteases, lipoxigenases
In the meat industry, what enzymes are used for tenderization and solubilization?
Proteases: papain & bromelain
In the meat industry, what enzymes are used for texturization?
transglutaminase - firm texture
What enzyme does high fructose corn syrup use?
glucose isomerase
What are 5 important oxidoreductases in food processing?
- polyphenol oxidase
- peroxidase
- lipoxygenase
- glucose oxidase
- ascorbic acid oxidase
What oxidoreductase enzyme is heat stable?
Peroxidase
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
Peroxidase is used as an index for what?
High heat treatment
What reaction does glucose oxidase catalyze?
glucose + O2 –> gluconic acid + H2O2
What are3 results in foods after the application of glucose oxidase?
- de-sugaring
- pH decrease
- O2 removal (reduce oxidation)
What oxidoreductase enzyme is very heat sensitive?
ascorbic acid oxidase
What reaction does ascorbic acid oxidase catalyze?
Ascorbic acid + O2 –> dehydroascrobic acid + O2
What is ascorbic acid?
Vitamin C
Are proteases highly specific?
Yes
What are the 2 major COHs found in foods?
starch and cellulose
Out of starch & cellulose, which one is much more resistant to enzymatic hydrolysis?
Cellulose
What 2 enzymes hydrolyze starch?
- Amylase
2. Glucoamylase
What enzyme hydrolyses cellulose?
Cellulase
What are 4 traditional methods for controlling enzymatic reactions in foods based on Temperature?
blanching, freezing, chilling, pasteurization
What are 2 traditional methods for controlling enzymatic reactions in foods based on Aw?
salting, dehydration
What are 4 traditional methods for controlling enzymatic reactions in foods based on Chemicals?
sulfites, acids, alkalis, antioxidants, chelating agents
What is a novel method for controlling enzymatic reactions in foods based on high pressure treatment?
ultra high pressure processing
What is a novel method for controlling enzymatic reactions in foods based on enzyme treatment?
killer enzymes/anti-enzyme enzymes
What are 3 other types of novel methods for controlling enzymatic reactions in foods?
Enzyme inhibitors, Microwave, Ultrasonic
+ High pressure treatment, Enzyme treatment
