Transcript Food Enzymes: Friend or Foe? A Great Teaching Topic

Food Enzymes:
Friend or Foe?
A Great Teaching Topic
Dr. S. Suzanne Nielsen, Purdue University,
Dept. Food Science, [email protected]
Enzymes in the Food Industry - Friend or Foe?
 What are enzymes?
 What controls the action of enzymes?
 Why are enzymes important in the
food industry?
 Examples of enzymes used in the food
industry.
What are enzymes?
 Enzymes are highly specialized proteins
that catalyze specific biochemical
reactions
 Proteins are chains of individual amino
acids
Enzymes catalyze reactions
such as these:
Starch


-----



Sucrose


Proteins

Glucose
   

Glucose

+
Fructose

Amino Acids

What controls the action of
enzymes?
 Temperature
 Water Content
 pH
 Chemicals
 Alteration of Substrates
 Alteration of Products
Why are enzymes important in
the food industry?
 Added or used to cause particular reaction

Advantages






Natural, Nontoxic
Catalyze specific reactions
Active under mild conditions
Active at low concentrations
Can control rate of reaction
Can be inactivated
Why are enzymes important in
the food industry?
 Naturally present – may want to
inactivate them
 Naturally present – may want them to
act
 Used as indicators of proper
processing
 Used to measure another compound
in the food
Experiments with Food Enzymes
 Enzymatic Browning of Fruits and
Vegetables
 Coagulation of Milk by Rennet Addition
Enzymatic Browning of Fruits
and Vegetables
 Apple (or potato, banana, etc.) slice is put
in each of the following solutions. The
browning is observed at 5, 10 , and 20
minutes.





Control (no solution; open to air)
Water Only
0.1% acetic acid
0.1% citric acid
0.1% ascorbic acid
Samples at 5 minutes
Control
Samples at 10 minutes
Control
Samples at 20 minutes
Control
Control
Water
0.1% Acetic Acid
0.1% Citric Acid
0.1% Ascorbic Acid
Why?
 Ascorbic acid – Acts as antioxidant; Oxygen
preferentially oxidized the ascorbate and not the
phenolic compounds
 Citric acid – Acts as a chelating agent;
Complexes copper ions that are necessary for
enzyme activity
 Acetic acid – a strong organic acid; Reduces the
pH below 3.0 and irreversibly inactivates the
enzyme
 H2O – Oxygen is necessary for the browning
reaction; Immersion in H2O restricts the available
oxygen
Experiments with Food Enzymes
 Enzymatic Browning of Fruits and
Vegetables
 Coagulation of Milk by Rennet Addition
Coagulation of Milk by Rennet
Addition
 Pipette 10 ml of milk into each of 3 test
tubes.
 To two of the tubes, add ~1.5 ml of a 1%
rennet solution.
 Mix. (The 3rd tube will serve as a control.
It contains no rennet).
 Place one of the two tubes with rennet into
water at ~37C
 Observe the coagulation.
Coagulation of Sample
 Control
Coagulation of Sample
 1% Rennet Solution, No Heat
5 minutes
10 minutes
20 minutes
Coagulation of Sample
 1% Rennet Solution, 37C
5 minutes
10 minutes
20 minutes
Why?
 Rennet




An enzyme obtained from fourth stomach of
ruminant animals, and from some microorganisms
Cleaves particular bond in K-casein of milk to
initiate milk coagulation
Coagulates milk protein in cheese making
Aids in development of flavor and texture in
ripened cheese.
 Mild heat speeds up the enzyme reaction.
Other Examples of Enzymes in Foods
 Milk
 Lactase
 Alkaline phosphatase
 Lipases
 Plasmin
 Fresh vs. canned pineapple
 Bromelain breaks down gelatin in “Jello”
 Meat tenderizer – uses bromelain, ficin, or papain
 Blanching of vegetables – catalase and peroxidase
 Cloudy vs. clear apple juice
 Mandarin oranges
 Onions – enzyme alliinase acts on sulfur cmpds.
Enzymes in the Food Industry - Friend or Foe?
 What are enzymes?
 What controls the action of enzymes?
 Why are enzymes important in the
food industry?
 Examples of enzymes used in the food
industry.
Food Enzymes:
Friend or Foe?
A Great Teaching Topic
Dr. S. Suzanne Nielsen, Purdue University,
Dept. Food Science, [email protected]
Questions?