Why does a cut apple turn brown on the table?
Look… a juicy apple, cut wide open. The air all around us is full of tiny invisible bits. Here are two slices waiting together — this one is bare, and this one we rubbed with a little lemon. The air will touch them both. So tell me… which slice do you think will turn brown?
After you watchWhy does a cut apple turn brown on the table?
The short answer
A cut apple turns brown because the air touches the wet inside that was hidden until you cut it. Tiny bits in the air, called oxygen, meet the apple's own juice and slowly make a brown color, a bit like how metal can go rusty. Rubbing lemon on the cut makes a sour shield that stops the air, so the apple stays white.
The whole story
How it works
Cutting the apple opens up its juicy inside, which used to be sealed under the skin. Now oxygen from the air can touch the apple's juice, and together they make a new brown color on the cut. Lemon juice is sour and helps grab the air bits first, so the browning can't get going and the apple stays pale.
What people get wrong
It is easy to think the apple is going bad or drying out, but it is not rotting at all. Even a fresh, juicy apple goes brown in a few minutes. It is just the air meeting the cut, and lemon can keep it white.
Questions kids ask
Is a brown apple okay to eat?
Usually yes. A brown apple is not rotten, it has just met the air. It may look less pretty but it is still fine to eat. Truly spoiled food smells bad or feels mushy, which is different.
Why does lemon keep it white?
Lemon is sour, and that sourness makes a little shield on the cut apple. It grabs the air bits before they can touch the apple's juice, so the brown color never gets to start.
Keep going
What else makes you wonder?
- If the air makes a cut apple brown, why doesn't a whole apple in the bowl go brown?
- What other foods turn brown after you cut or peel them?