Enzymatic Browning Experiment
Experiment: Coat each of seven 3/4-inch banana and/or 3/4-inch apple slices with one of the following:
1. A solution of I Tbsp. sugar or corn syrup and 1/4 c. water.
2. A solution of I tsp. lemon juice and 1/4 c. water.
3. A solution of I tsp. cream of tartar and 1/4 c. water.
4. A solution of 1 Tbsp. ascorbic acid and 1/4 c. water.
5. A solution of 1/8 tsp. sodium bisulfite and 2/3 c. water. (Note: sodium bisulfite can be purchased through a pharmacy.)
6. 1/4 c. water.
7. Put in petri dishes and expose to the open air.
NOTE TO TEACHER: Background information on enzymatic browning.
Enzymes are organic catalysts (proteins) produced by living cells which can be destroyed by heat. They are responsible for some of the changes that take place in the flavor, color, and texture of foods.
Browning results from the fresh fruit being exposed to air. This browning takes place IMMEDIATELY after the cut fruit is exposed to air and is a process called oxidation. Browning is not a reversible process. Fruit which has browned cannot be restored to its original color by placing it into a solution.
High-acid fruits do not brown when exposed to air. Fruits such as bananas deteriorate in texture as they sit in a liquid solution.
Prevent browning by covering the fruit immediately after peeling or slicing with a juice containing Vitamin C or a citric acid solution, salt water, or anything that covers the surface of the fruit and slows the oxidation process.
Placing peeled fruit in water to prevent it from turning dark causes loss of water-soluble vitamins, minerals, and natural sugars.
When air comes in contact with a fruit which is low in Vitamin C (ascorbic acid), the air oxidizes or browns the surface of the fruit.
Because oxidation or browning takes place during the first few minutes that fruit is exposed to air, it is important that we cover fruit as soon as it is peeled.
Procedure for Obtaining a Standard Product:
Prevent browning (or oxidation) by covering the fruit immediately after peeling it with a juice containing a high Vitamin C content, water, salad dressing, etc.