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Why Do Apples Turn Brown?

Updated: Jul 11, 2023

Apples turning brown

One of my go-to afternoon snacks is a juicy apple. I’ll slice it up and bring the plate to my

workspace where I can take my time and enjoy it with some peanut butter. But just 3 minutes after cutting, all the apple slices have started to brown. Why does this happen?

When an apple is sliced or bruised, apple cells break apart and an enzyme called polyphenol oxidase gets exposed to the oxygen.[1] This enzyme induces a reaction between polyphenols (plant compounds) and oxygen, which generates dark pigments that turn the apple brown.[2] The whole process is known as “enzymatic browning” and is common in other foods such as bananas, pears, and avocados.

Apples are still safe to eat after they turn brown, but the flavor will change slightly. It’s simply a personal preference.

How can browning be prevented?

If you would rather not eat an apple that is turning brown, here are a few ways to help prevent or slow the browning process:

1. Immediately store the apples in an airtight container after slicing to reduce their exposure to oxygen.

2. Squeeze some lemon, lime, or orange juice on the slices – the citric acid slows the chemical reaction that leads to browning.

3. Stir 2 tablespoons of honey into 1 cup of water and soak the slices in the water for 30 seconds. A compound in honey not only slows the reaction, but also adds extra sweetness to the fruit. [3]

[1] (Scientific American, 2007) [2] (Holderbaum, Kon, Kudo, & Guerra, 2010) [3] (Prakash, 2019)

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