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Why do apples bruise? © Getty Images

Why do apples bruise?

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A chemical reaction occurs once the apple's cells are opened up and mixed with oxygen causing the delicious flesh to go brown.

Asked by: Faye Lynch Williams (15 years old)

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Cutting or dropping an apple causes compartments inside the cells, including the central storage sacs (vacuoles), to burst open, allowing chemicals to mix and oxygen to flood in and catalyse reactions.

In particular, chemicals in the vacuole called polyphenols come into contact with an enzyme called polyphenol oxidase, which is present in every cell in the apple. It’s this reaction that leads to the brown, unappetising ‘melanin’ chemicals that we see on a sliced or bruised apple.

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Authors

Dr Emma Davies is a science writer and editor with a PhD in food chemistry from the University of Leeds. She writes about all aspects of chemistry, from food and the environment to toxicology and regulatory science.

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