Food Science: Why Sliced Fruit Turns Brown

published May 20, 2008
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(Image credit: Apartment Therapy)

One of the things we love more than anything else this time of year is a big bowl of fresh fruit, especially with a generous dollop of yogurt or creme fraiche on top!

Unfortunately, in the time between cutting and serving, these salads can go from a pretty mix of crisp fruits to a slimy brown mess. Apples and pears are particularly prone to this phenomenon, caused by a reaction between enzymes in the fruits and the air in your kitchen.

When you cut into a piece of fruit, cells within the fruit are microscopically bruised and release an enzyme called polyphenol oxidases. This enzyme reacts with both the air and other enzymes in the fruit to cause that brown discoloration and, sometimes, off flavors.

Avocados, bananas, artichokes, and potatoes are also prone to this browning process.

Once a fruit is cut, nothing can completely stop the oxidization process from happening. But there are several things we can do to slow it down.

  • Prepare your salad as close as possible to when you’re planning to serve it.
  • Use a sharp knife. This minimizes the microscopic bruising.
  • Toss the salad with lemon or lime juice. This is one trick we learned from our mothers that is based in good science! The acid in citrus fruits inhibits and slows the chemical reaction causing oxidization.

There are also some powders available on the market that you can sprinkle over fruit to stop browning. Most of these are made of asorbic acid (Vitamin C) and sugar.

Related: Are Bananas Going Extinct?

(Image: Flickr member 46137 licensed under Creative Commons)