Enzymes III Flashcards
Beneficial aspects of using enzymes in food industry
- Natural, non-toxic
- Specificity uniform products
- Efficient small amount under mild reaction conditions
- Enzymes can be inactivated by heating or pH. Treatment after desired catalysis achieved.
- Enzyme can be recovered and reused.
∇ “immobilized enzyme” – protein is hydrolyzed by trypsin. So the enzymes are immobilized on resin or on some other material. We want to hydrolyze the protein by trypsin to get protein hydrolytes. For hydrolysis we need to inactivate trypsin bc otherwise we will get amino acids. So we kill trypsin. But if we want to recover trypsin, we immobilize it by resin or some other material so that we use centrifugation to separate them and reuse the enzyme.
What is an immobilized enzyme?
- provide increased resistance to changes in conditions such as pH or temperature.
- It also lets enzymes be held in place throughout the reaction, following which they are easily separated from the products and may be used again
- a far more efficient process and so is widely used in industry for enzyme catalysed reactions.
Give an example for an immobilized enzyme
∇ protein is hydrolyzed by trypsin. So the enzymes are immobilized on resin or on some other material.
We want to hydrolyze the protein by trypsin to get protein hydrolytes.
For hydrolysis we need to inactivate trypsin bc otherwise we will get amino acids. So we kill trypsin. But if we want to recover trypsin, we immobilize it by resin or some other material so that we use centrifugation to separate them and reuse the enzyme.
Deleterious aspects of using enzymes in food industry
- Enzymatic browning by PPO
- Spoilage
- Safety issue
Reaction of Enzymatic browning by PPO
MONOPHENOL/DIPHENOL+ 02 –PPO O-quinone –polymerization melanin
Give an example for an enzyme that changes the texture in food spoilage
pectinase and glycosidases hydrolyze the pectin and starch - soft texture
EX: banana
Give 3 example for an enzyme that changes the flavour in food spoilage
lipoxygenase (LOX) catalyzes the oxidation of unsaturated fatty acids causing odor in foods.
EX: beans – beany flavor
Unsaturated fatty acids + O2 -LOX fatty acid hydroperoxide
lipase: cause rancid odor
triglycerides + O2 –lipase glycerol + fatty acids
fatty acids are not stable molecules so they can easily get oxidized and give rancid odor.
Protease: may form bitter peptides in protein foods. If we add more protease it breaks down the molecule to amino acids giving more flavor the food. So in this case you add more protease. However, intensive hydrolysis using protease for de-bitterness,
Which enzyme gives rancid odour?
lipase: cause rancid odor
triglycerides + O2 –lipase glycerol + fatty acids
fatty acids are not stable molecules so they can easily get oxidized and give rancid odor.
Which enzymes causes bitter taste in food?
Protease: may form bitter peptides in protein foods. If we add more protease it breaks down the molecule to amino acids giving more flavor the food. So in this case you add more protease. However, intensive hydrolysis using protease for de-bitterness,
Why is using enzymes a safety issue?
♣ Histidine —histidine decarboxylase histamine + CO2
Histamine is toxic and gives an off-odor.
How are desirable effects and undesirable effects relative? Give examples for some undesirable effects used as desirable effects
- PPO –> black tea, coffee
- LOX –> blanching flour by degrading pigments
- Lipase –> flavor
- Protease –> flavor
Sources of industrial enzymes
- Plant
- Animal
- Microbial
Plant sources of enzymes
∇ (3-5%) ∇ protease ∇ papain – papaya ∇ ficin – fig ∇ bromelain – pineapple
What is the percentage of plant sourced enzymes used in food industry?
3-5%
______ comes from papayas
papain
______ comes from figs
ficin
______ comes from pineapples
bromelain
Animal sources of enzymes
∇ (6-7%) ∇ digestive protease ∇ trypsin ∇ chymotrypsin ∇ rennet
What is the percentage of animal sourced enzymes used in food industry?
6-7%
Give examples for animal sourced of enzymes
∇ digestive protease
∇ trypsin
∇ chymotrypsin
∇ rennet
Microbial sources of enzymes
∇ It is the most common source of enzymes (80-90%)
∇ They grow fast
∇ They need only limited spaces and nutrients
∇ Cheap to grow
∇ Protease cocktail
∇ Transglutamniase
∇ Amylase
What is the percentage of microbial sourced enzymes used in food industry?
80-90%
Benefits of using microbial enzymes
∇ They grow fast
∇ They need only limited spaces and nutrients
∇ Cheap to grow
Give examples for microbial enzymes
∇ Protease cocktail
∇ Transglutamniase
∇ Amylase
Give examples for some uses of enzymes in food industry
- cheesemaking
- winemaking and brewing
- baking
- meat industry
- High fructose concentration syrup production with glucose isomerase
Give examples of enzymes that are used for cheesemaking
- rennet (contains chymosin/rennin)
- pepsin
Give examples of enzymes that are used for winemaking and brewing
- proteases
- amylases
Give examples of enzymes that are used for baking
- amylases
- proteases
- lipoxygenase
Give examples of enzymes that are used in meat industry
proteases (tenderization, solubilization)
papain
bromelain
Transglutamniase - catalyze the cross-linking of proteins to form firm texture. (meat recombination, meat restructuring)
How does Transglutaminase affect the meat?
catalyze the cross-linking of proteins to form firm texture. (meat recombination, meat restructuring)
How does protease affect the meat?
(tenderization, solubilization)
High fructose concentration syrup production with _________ (name of the enzyme)
glucose isomerase
Chemical reactions of oxidoreductases in foods (5)
- PPO
- Peroxidase
- Lipoxygenase (LOX)
- Glucose oxidase
- Ascorbic acid oxidase
Peroxidase activity in food (oxidoreductase)
∇ Index of high temperature treatment in foods.
∇ Heat stable
∇ Fresh broccoli – sterilization –> ready to eat broccoli salad
There is no obvious difference, fresh, juicy etc.
In order to test the food sterilization, you take both kinds of broccoli and you check the peroxidase activity, the first possibility is that you found the ready to eat peroxidase activity is low – this means they used high temperature for sterilization.
If you get a result, the peroxidase activity is the same one as the fresh one, this means that they didn’t do any treatment on the broccoli. By using peroxidase, you can determine whether the food was treated with heat.
How do you test the food sterilization?
In order to test the food sterilization, you take both kinds of broccoli and you check the peroxidase activity, the first possibility is that you found the ready to eat peroxidase activity is low – this means they used high temperature for sterilization.
If you get a result, the peroxidase activity is the same one as the fresh one, this means that they didn’t do any treatment on the broccoli. By using peroxidase, you can determine whether the food was treated with heat.
Glucose oxidase activity in food (oxidoreductase)
∇ Oxidize glucose into gluconic acid
Glucose + O2 –GOD gluconic acid + H202
♣ De-sugaring
♣ Decreases pH.
♣ O2 removal
Ascorbic acid oxidase activity in food (oxidoreductase)
∇ Vitamin C + O2 – ascorbic acid oxidase dehydroascorbic acid
Chemical reactions of hydrolases in foods (3)
- Chemical Reaction of Proteases
- Chemical Reactions of Carbohydrases
- Chemical Reactions of Lipases
Important oxidoreductases in food processing
- polyphenol oxidase
- peroxidase
- lipoxygenase
- glucose oxidase
- ascorbic acid oxidase
Protease activity
protease (also called a peptidase or proteinase) is any enzyme that performs proteolysis; protein catabolism by hydrolysis of peptide bonds. Proteases have evolved multiple times, and different classes of protease can perform the same reaction by completely different catalytic mechanisms.
Protease specificity (trypsin)
These enzymes contain a catalytic triad consisting of histidine-57, aspartate-102, and serine-195. These three residues form a charge relay that increases nucleophilicity of the active site serine.
Carbohydrase Activity
- Starch & cellulose - the 2 major carbohydrates found in foods
- Cellulose much more resistant to enzymatic hydrolysis than starch
- Amylase, glucoamylase, etc. hydrolyze starch
- Cellulase hydrolyzes cellulose
True/False
Cellulose much more resistant to enzymatic hydrolysis than starch
true
Enzymes that can hydrolyze starch
Amylase, glucoamylase, etc. hydrolyze starch
Cellulose is hydrolyzed by _______
cellulose
2 ways of controlling enzymatic activity in food.
Traditional method
Novel method
Traditional method of controlling enzymatic activity based on temperature
(e.g., blanching, freezing, chilling, pasteurization)
Traditional method of controlling enzymatic activity based on Aw (water activity)
e.g., salting; dehydration
Traditional method of controlling enzymatic activity based on chemicals
(e.g., sulfites, acids, alkalis, antioxidants, chelating agents)
Novel method of controlling enzymatic activity based on high pressure treatment
(e.g., ultra high pressure processing)
Novel method of controlling enzymatic activity based on enzyme treatment
(killer enzymes / anti-enzyme enzymes)
Traditional ways of controlling enzymatic activity
temperature
water activity
based on chemicals
Novel ways of controlling enzymatic activity
high pressure treatment enzyme treatment enzyme inhibitors microwave ultrasonic
