Food Enzymes Friend or Foe A Great Teaching

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? n What are enzymes? n What controls the action of enzymes? n Why are enzymes important in the food industry? n Examples of enzymes used in the food industry.

What are enzymes? n Enzymes are highly specialized proteins that catalyze specific biochemical reactions n 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? n Temperature n Water Content n p. H n Chemicals n Alteration of Substrates n Alteration of Products

Why are enzymes important in the food industry? n Added or used to cause particular reaction n Advantages n n n 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? n Naturally present – may want to inactivate them n Naturally present – may want them to act n Used as indicators of proper processing n Used to measure another compound in the food

Experiments with Food Enzymes n Enzymatic Browning of Fruits and Vegetables n Coagulation of Milk by Rennet Addition

Enzymatic Browning of Fruits and Vegetables n 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) n Water Only n 0. 1% acetic acid n 0. 1% citric acid n 0. 1% ascorbic acid n

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? n Ascorbic acid – Acts as antioxidant; Oxygen preferentially oxidized the ascorbate and not the phenolic compounds n Citric acid – Acts as a chelating agent; Complexes copper ions that are necessary for enzyme activity n Acetic acid – a strong organic acid; Reduces the p. H below 3. 0 and irreversibly inactivates the enzyme n H 2 O – Oxygen is necessary for the browning reaction; Immersion in H 2 O restricts the available oxygen

Experiments with Food Enzymes n Enzymatic Browning of Fruits and Vegetables n Coagulation of Milk by Rennet Addition

Coagulation of Milk by Rennet Addition n Pipette 10 ml of milk into each of 3 test tubes. n To two of the tubes, add ~1. 5 ml of a 1% rennet solution. n Mix. (The 3 rd tube will serve as a control. It contains no rennet). n Place one of the two tubes with rennet into water at ~37 C n Observe the coagulation.

Coagulation of Sample n Control

Coagulation of Sample n 1% Rennet Solution, No Heat 5 minutes 10 minutes 20 minutes

Coagulation of Sample n 1% Rennet Solution, 37 C 5 minutes 10 minutes 20 minutes

Why? n Rennet n n 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. n Mild heat speeds up the enzyme reaction.

Other Examples of Enzymes in Foods n Milk n Lactase n Alkaline phosphatase n Lipases n Plasmin n Fresh vs. canned pineapple n Bromelain breaks down gelatin in “Jello” n Meat tenderizer – uses bromelain, ficin, or papain n Blanching of vegetables – catalase and peroxidase n Cloudy vs. clear apple juice n Mandarin oranges n Onions – enzyme alliinase acts on sulfur cmpds.

Enzymes in the Food Industry - Friend or Foe? n What are enzymes? n What controls the action of enzymes? n Why are enzymes important in the food industry? n 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?