Food Enzymes: Friend or Foe? A Great Teaching Topic Dr. 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? 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 ~37C 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, 37C 5 minutes 10 minutes 20 minutes
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.
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, nielsens@purdue.edu
Questions?