Catalase Enzyme Test

Introduction:

All living matter is composed of enzymes that take part in metabolic processes of living plants. These enzymes are still functioning and affect the quality of fruits and vegetables after they are harvested. Additionally, these enzymes act as organic catalysts and are capable of causing many undesirable changes in foods. Thus, the enzymes should be inactivated as soon as possible.

One way of inactivating the enzyme is by blanching the product. Blanching is a short heat treatment (steam or water) that inactivates the enzyme that causes food to change in color, texture, or flavor.

A simple test that can be done to determine if catalase has been inactivated is to apply hydrogen peroxide (H ₂ O ₂ ) to the food product. The only catalytic action possessed by catalase is the decomposition of hydrogen peroxide. This is detected by monitoring the end products of the reaction, water and gaseous oxygen.

2H ₂ O ₂ --> 2H ₂ O + O ₂

The range for optimum catalase activity is 0 degrees C to 10 degrees C. Thus, as the temperature exceeds the limit catalase is rapidly destroyed due to thermal breakdown.

Materials:

3% Hydrogen Peroxide
2 500 ml beakers
Lab Squirt bottle - 250 ml
Knife to cut the food product
2 small plastic plates
Timer
Hot plate
Tongs
Tap water
Raw vegetables or fruits

Products that work well are: bing cherry, Brussel sprouts, sweet potatoes, kiwi, mushroom. You may want to try others. However, fruits and vegetables with white flesh make it difficult for students to see the reaction.

Reference:

Burns, E.E. "Laboratory Manual for FSTC/HORT 311 - Principles in Food Processing." Texas A&M University. College Station, TX.

Procedures:

1. Prepare vegetables into sizes that would be desirable for freezing. (They should be small enough to fit in a beaker).
2. Place one piece of a raw vegetable on a small plate. Cut a piece off and apply 2ml of hydrogen peroxide to the cut surface of the vegetable. If the piece of vegetable is large you may have to apply more hydrogen peroxide. Make sure the vegetable surface is covered with hydrogen peroxide.
3. Prepare a 500 ml beaker with tap water. Bring to a boil on a hot plate.
4. Place a piece of raw vegetable in the boiling water for 1 minute.
5. Remove the vegetable from the boiling water with tongs. Place the vegetable in a beaker of cold water until it is cooled. (About 3-5 minutes)
6. Repeat step #2. However, at this point the vegetable is not raw it will be cooked for 1 minute.
7. If foaming occurs again then repeat steps #4 and #5.
8. Continue with this boil 1 minute followed by the H ₂ O ₂ test until no foaming occurs when H ₂ O ₂ is applied. Make sure to record your data in the table.
9. Repeat the procedures with the next vegetable.

Results:

Blanch	Vegetable #1	Vegetable #2	Vegetable #3
Fresh vegetable
1 minute
2 minute
3 minute
4 minute
5 minute

Questions:

1. What is the purpose of blanching?
   
   
   
   
2. What should be your primary consideration in selecting a blanching time for any vegetable or fruit product?
   
   
   
   
3. Write the chemical equation for the break down of hydrogen peroxide catalyzed by catalase.
   
   
   
   

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