Kitchen Science 2-minute video · ages 4-8 · free coloring page
Why do apples turn brown after we cut them?
You cut an apple, and the inside is white and fresh. But leave it on the plate for a while, and it turns brown! Why?
2 min
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Free coloring page
The scene from the video as a coloring page, plus the three-sentence answer, the experiment, and a QR code back to this page. One sheet, US Letter, black and white.
The answer in three parts
Why?
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An apple is made of millions of tiny rooms, called cells.
They are much too small to see. Each one is like a little bag, full of juice. When a knife cuts through, it breaks open the cells, and their juice spills out onto the cut side.
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The juice meets the air.
Air has a gas in it called oxygen. It is the same gas that you breathe in. Some things in the juice meet the oxygen, and they join together. When they join, they make something new, and it is brown.
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A tiny helper makes it happen fast.
The helper in the juice is called an enzyme. In just a few minutes, the brown starts to show.
For grown-ups: As long as an apple is whole, its inside stays white: the skin wraps it up tight and keeps the air out. To keep a cut slice white, lemon juice works because the sour juice slows the enzyme way down. Another trick is to keep the air away: wrap the slices up tight, or put them in a box with a lid. Less air means less brown.
Who else turns brown?
- Bananas
- Pears
- Avocados
- Potatoes
They all turn brown the same way as apples.
A tiny experiment
Try it!
The lemon test
You need: an apple, a little lemon juice, and a grown-up to cut the slices
- Ask a grown-up to cut an apple into slices.
- Rub lemon juice on one slice, and leave another slice plain.
- Put them side by side, wait half an hour, and look. Which one is browner?
What happened? Lemon juice is sour, and that sour juice slows the little helper way down.
Did you know?
Is a brown apple bad? No! It is still safe to eat. It just looks different, and it may feel a little softer.
Your guide in this video
I'm Pip, a little red apple. Today we will solve a fruity mystery!
Pip is a little red apple. As long as Pip is whole, Pip's skin keeps the air out, so the inside stays white.
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