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Aug 24, 2009

Keep a Cut Apple from Turning Brown

When you cut open an apple, an enzyme (tyrosinase) in the flesh reacts with oxygen to turn polyphenols into melanin (the same pigment that makes you tan). Here's how to halt the process so your apples stay bright and white.

Choose apples that are less prone to browning. A study found that Arangeh tend to brown the least. Granny Smith and Golden Smoty apples also showed minimal browning. Golden Delicious apples were in the middle, and Red Delicious apples browned the most.Cut the apple underwater. This keeps the enzyme from making contact with oxygen. Keep the cut apple in the water until ready to serve. Coat the exposed flesh in acid. By bringing the pH below 2, the enzyme that makes the apple flesh turn brown is deactivated.[3] Here are some acids you can use:
Ascorbic acid, better known as vitamin C. Look for it in the canning section or pharmacy as powder. Apply directly or dissolved in water (1/2 tsp. per 2 1/2 cups of water
Lemon or lime juice. It's not as effective as ascorbic acid, but it'll do in a pinch, and they're more readily available. The juice can be diluted up to 3:1. Lemon juice will have a less obvious taste than lime juice. Blanch the apples. This will denature the enzyme. Let the apple sit in boiling water for one or two minutes, then rinse with cold water. They can then be eaten, frozen, or used for apple pie. Cover exposed apple flesh tightly in plastic wrap. This will work best if you have half an apple (as opposed to pieces). Try to keep the creases on the exposed side to a minimal. This technique has allow to keep the air away from the apple flesh to prevent the the apple flesh from oxidizing. Soak apple pieces in a slightly salty water solution for a few seconds. Remove and enjoy white apple pieces for a considerable time. Works well if you're adding apples to a fruit salad.

These techniques will also work for potatoes. It's the same underlying mechanism. Also, the sharper the knife you use, the better.If you coat the apple with an acid, the flavor can be affected, and picky eaters might notice. Try sprinkling apples with Jello powder or Kool-aid powder. Jello adds sweetness. None of these techniques last indefinitely, but all are useful to keep the apples from turning brown for a few hours, for instance, if you wanted to include them on a cheese or fruit tray.

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