Why do apples turn brown?

You cut a juicy apple, take a few bites, and run off to play. When you come back, the white part has turned a yucky brown! The apple isn’t dirty or bad. Something invisible has been at work.

The inside meets the air

When an apple is whole, its skin keeps the soft inside safe. But the moment you cut it, the white inside is suddenly out in the open. Now it touches the air all around us.

The air has a gas in it called oxygen. Oxygen is great for breathing, but it does something funny to a cut apple.

A colour-changing reaction

Inside the apple are special tiny helpers. When they meet oxygen, they start a reaction — a sort of mix that makes a new brown colour. This is called browning.

It is a bit like how a bike left in the rain can go rusty. The apple isn’t broken; it has just changed colour because of the oxygen. It is still safe to eat.

A squeeze to slow it down

Want to keep your apple white for longer? Squeeze a little lemon juice on the cut part. Lemon juice gets in the way of the oxygen, so the browning happens much more slowly. Clever trick!

Wonder fact: Bananas, pears, and potatoes turn brown for the same reason — they all react with oxygen in the air.