- An apple
- A round orange slice (Try a fruit store!)
- A fruit knife (Can be obtained from a general store or a convenience store)
- At first cut the apple in half using a knife.
- Now place the round slice of the orange over the white part of one half of the apple.
- Leave the other half of the apple uncovered.
- Now leave them like this for about two hours.
- Record any kind of difference in their appearance.
- The uncovered half of the apple should turn brown.
- The apple half which is covered with the orange slice should not turn brown.
Each apple cell contains a special chemical which is called polyphenol oxidase or PPO. When an apple is cut or sliced, some of the cells are opened in the environment and the PPO is to the air surrounding it. This allows PPO to react with the oxygen in the air. The process in which it reacts is called oxidation. This chemical reaction is what causes the apple slice turn brown.
One way to prevent the oxidation reaction is to prevent the oxygen from reaching PPO inside the apple cells. Normally it is done by submerging the apples in the water or by wrapping them tightly in a plastic wrapper. In another way we can add ascorbic acid to the apples to prevent the oxidation reaction from taking place. The ascorbic acid is also known as vitamin c.
Orange juice contains a lot of vitamin c or ascorbic acid. Placing the apple half in contact with the orange slice makes the ascorbic acid to reach the apple cells which prevents oxidation from happening. In addition, the orange slice placed over the white part of the apple half also acts as a barrier preventing oxygen from reaching the PPO. So this way orange can prevent apples from browning.
An alternative way to prevent the apples from browning is to cook them. Heat from the cooking makes the polyphenol oxidase or PPO molecules to break. Since this chemical is what causes the oxidation reaction or browning reaction, breaking it up will prevent the reaction. It’s that simple!
MORE EXPERIMENTS FOR YOU:
- Instead using the whole orange slice try using only the orange juice.
- Try using other fruits containing vitamin c or ascorbic acid such as – lemon, lime, pineapple etc.
- Try to compare which is best for preventing browning of the apple.