Food%20Enzymes:%20Friend%20or%20Foe?%20A%20Great%20Teaching%20Topic

1
Food Enzymes Friend or Foe? A Great Teaching
Topic

• Dr. S. Suzanne Nielsen, Purdue University,
• Dept. Food Science, nielsens_at_purdue.edu

2
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.

3
What are enzymes?

• Enzymes are highly specialized proteins that
  catalyze specific biochemical reactions
• Proteins are chains of individual amino acids

4
Enzymes catalyze reactions such as these
Starch ? Glucose
? ?
?-?-?-?-?-? ? ? ? ?
? ? Sucrose
? Glucose Fructose
??? ? ?
Proteins ?
Amino Acids ??????????? ? ?
? ? ? ?
5
What controls the action of enzymes?

• Temperature
• Water Content
• pH
• Chemicals
• Alteration of Substrates
• Alteration of Products

6
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

7
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

8
Experiments with Food Enzymes

• Enzymatic Browning of Fruits and Vegetables
• Coagulation of Milk by Rennet Addition

9
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

10
Samples at 5 minutes

• Control

11
Samples at 10 minutes

• Control

12
Samples at 20 minutes

• Control

13
Control
14
Water
15
0.1 Acetic Acid
16
0.1 Citric Acid
17
0.1 Ascorbic Acid
18
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

19
Experiments with Food Enzymes

• Enzymatic Browning of Fruits and Vegetables
• Coagulation of Milk by Rennet Addition

20
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.

21
Coagulation of Sample

• Control

22
Coagulation of Sample

• 1 Rennet Solution, No Heat

5 minutes 10 minutes 20 minutes
23
Coagulation of Sample

• 1 Rennet Solution, 37?C

5 minutes 10 minutes 20 minutes
24
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.

25
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.

26
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.

27
Food Enzymes Friend or Foe? A Great Teaching
Topic

• Dr. S. Suzanne Nielsen, Purdue University,
• Dept. Food Science, nielsens_at_purdue.edu

28

• Questions?