Book 1, Question 128
Why Do Apples Turn Brown? A Chemical Suntan!
Cut an apple and it starts to brown. The cut lets oxygen in, and an enzyme in the apple cells meets natural compounds and browns them. Acids in lemon juice slow the enzyme and help protect the apple. The page says the brown is a chemical suntan, not rot yet, and that the apple is safe to eat, just not as pretty. Try one plain slice and one with lemon juice and check in 15 minutes.
From the book
Page from A Million Whys Book 1
More fun facts
- The browning is called enzymatic browning, and it is one of the biggest causes of fruit and vegetable spoilage.
- The enzyme that does it is called polyphenol oxidase, or PPO for short.
- The brown color is melanin, the same pigment that colors human hair, skin and eyes.
- In a whole apple, the enzyme and the chemicals it acts on are kept apart in different parts of the cells.
- Bananas, peaches, pears, mushrooms and lettuce can turn brown too.
- Browned fruit is safe to eat. It just looks less appealing and loses some crunch.
- Juices with lots of vitamin C, like orange, pineapple, lemon and lime, can slow down browning.
Sources: Science News Explores, Illinois
Questions kids ask
Is a brown apple safe to eat?
Yes. Browning is harmless, but the apple may be less crisp.
How can I keep apple slices from browning?
Dip them in a juice with lots of vitamin C, like orange, pineapple or lemon juice.