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Why do apples turn brown when you cut them? Why does it help if you put them in the refrigerator?
Question Date: 2002-02-16
Answer 1:

Brown apples are just as good. Remember these yummy apple pies with brown apples on top?

Apples turn brown when exposed to air because of the oxidation process that goes on when the inside of the apple gets exposed to the ambient air which contains oxygen and water molecules. The skin of the apple protects it from this process. This oxidation process is very sensitive to the ambient temperature.

For example if you place the peeled apple in the refrigerator the process is greatly slowed down and it will take several days before it turns brown. If you place it in the hot oven it will turn brown very quickly . Faster than if you left it exposed to air at room temperature.

Question to you: What would happen if you place the apple in a jar of oil? Would it turn brown?. Ask your teacher or try the experiment.

Good luck with your science class and your wise questions!

Answer 2:

The oxygen in the air (which makes up about 20% of the gas in air) is an extremely reactive gas. The outer skin of an apple acts to protect the inner pulp against injury. But if this layer is damaged, the cells in the pulp release enzymes which react with oxygen to oxidize the damaged cells and form a protective layer against infection. Thus, the brown coloration in an apple occurs in response to damage caused to the apple (similar to blood clotting in humans).

The reason a refrigerator helps to slow this down is because those enzymes responsible for causing the oxidation slow down when they get cold, so the colder it gets, the slower the browning occurs.

Answer 3:

Apples turn brown because of a chemical reaction called "oxidation", which is caused by oxygen from the air. Oxygen is one of the most reactive chemicals known, and there are many kinds of oxidation reactions. Others include burning, rusting, and the human body combining food with oxygen to produce the energy which runs essential functions (this is why you must eat and breathe in order to live).

All chemical reactions run slower at low temperatures, so putting apples in the fridge slows the browning despite the presence of oxygen. The fridge also slows the metabolic reactions of bacteria, thus making food take much longer to go spoil. The fridge does not stop chemical reactions, so bacteria will still rot the food eventually.

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