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Brown Bananas

based on 21 ratings
Author: Janice VanCleave

So You Want to Do a Project about Oxidation!

Let's Explore

Purpose

To determine if vitamin C can inhibit oxidation.

Materials

  • banana
  • dinner knife
  • 2 saucers
  • 2 sheets of white copy paper
  • pen
  • 3 vitamin C tablets (IOO-mg work well)
  • cutting board
  • rolling pin
  • timer

Procedure

  1. Peel the banana, and then slice it into eight pleces.
  2. Place four slices of banana in each saucer.
  3. Set each saucer on a sheet of paper. Label one of the papers ''Without Vitamin C." Label the other paper ''With Vitamin C."
  4. Place the vitamin C tablets on the cutting board and crush them with the rolling pin.
  5. Use the dinner knife to scoop up the vitamin C powder and sprinkle the powder over the cut surface of the banana slices in the With Vitamin C saucer.
  6. Every 15 minutes for 2 hours or more, observe the color of each sample's surface. Record your observation in an Oxidation Data table like the one shown.

Results

The untreated banana slices slowly turn brown, but those covered with vitamin Care unchanged.

Brown Banana

Why?

Bananas discolor when bruised or peeled and exposed to air. This discoloration is caused by changes that occur when the cells are broken. The chemicals released by the damaged cells are oxidized (combined with oxygen), resulting in changes in the fruit. This process of change due to a combination with oxygen is called oxidation. Vitamin C is an antioxidant, a substance that inhibits (decreases or stops) oxidation. Covering the surface of the banana with Vitamin C inhibits the discoloration caused by oxidation.

For Further Investigation

Lemons contain vitamin C. Would lemon juice stop the bananas from turning brown? A project question might be, How effective is lemon juice as an antioxidant?

Clues for your Investigation

  1. Repeat the investigation, adding a third test set of banana slices. Label the paper under the saucer ''With Lemon Juice."
  2. Use lemon juice squeezed from a fresh lemon.
  3. Photographs of the banana slices at the start, periodically during the test, and at the end of the test can be displayed to represent the progression of any changes. The photographs also help to compare the effectiveness of the antioxidants.

Brown Banana

References and Project Books

Church, Jok. You Can with Beakman: Science Stuff You Can Do. Kansas City, Kans.: Andrews & McMeel, 1993.

Kenda, Margaret, and Phyllis S. Williams. Science Wizardry for Kids. Hauppauge, N.Y.: Barron's, 1992.

Strauss, Michael. Where Puddles Go. Portsmouth, N.H.: Heinemann, 1995.

VanCleave, Janice.]anice VanCleave's Chemistry for Every Kid. New York: Wiley, 1989.

Wollard, Kathy. How Come? New York: Workman, 1993.

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