Food Enzymes: Friend or Foe? A Great Teaching Topic

Food Enzymes: Friend or Foe?

A Great Teaching TopicDr. S. Suzanne Nielsen, Purdue University, Dept. Food Science, nielsens@purdue.edu

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 Glucose

-----

Sucrose Glucose + Fructose

Proteins Amino Acids

What controls the action of enzymes?TemperatureWater ContentpHChemicalsAlteration of SubstratesAlteration 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 minutesControl

Samples at 10 minutesControl

Samples at 20 minutesControl

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 ~37C Observe the coagulation.

Coagulation of Sample Control

Coagulation of Sample 1% Rennet Solution, No Heat5 minutes 10 minutes 20 minutes

Coagulation of Sample 1% Rennet Solution, 37C5 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 TopicDr. S. Suzanne Nielsen, Purdue University, Dept. Food Science, nielsens@purdue.edu

Questions?