1. Food Enzymes: Friend or Foe? A Great Teaching Topic
Dr. S. Suzanne Nielsen, Purdue University,
Dept. Food Science,

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 Mild heat speeds up the enzyme reaction.
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,

28. Questions?