The Science Behind Brown Potatoes

• Peeled potatoes turn brown for the same reason cut fruit turns brown. Enzymes and phenols in the potatoes become oxidized when exposed to oxygen. The peeled potatoes begin to turn pink or brown shortly after they're peeled and cut. You can safely eat potatoes that have begun to discolor, but they do not look particularly appetizing.

Why Lemon Juice Works

• Lemon juice prevents browning -- not only on potatoes, but on cut fruit -- by destroying the enzymes in the potatoes. Lemon juice is an acid and effectively deforms enzymes on contact. Even when exposed to oxygen, the enzymes won't turn brown once they've been treated with lemon juice. This is also why potatoes in potato salad don't turn brown. The acidic vinegar in the mayonnaise attacks the enzymes and prevents discoloring.

The Lemon Juice Cure

• If you plan to cook potatoes right away, you don't need to treat them with lemon juice, but if you want to prep them ahead, a few sprinkles of lemon juice will keep them looking fresh. Place the cut and peeled potatoes in a bowl and add fresh or bottled lemon juice. Stir so each piece is thoroughly coated. Rinse the potatoes under cold water before you cook them to remove any lemon taste.

Other Options

• Lemon juice isn't the only solution for browning potatoes. Start by using a sharp knife to cut the potatoes, which seems to slow the browning process. Cover the potatoes in cold water, rather than lemon juice. The cold water acts as a barrier, preventing oxygen from reaching the potatoes. To increase the effectiveness of a water bath, add a few spoonfuls of lemon juice to the water or add a bit of citric acid. Citric acid is a white powder found in health food stores and some markets. People often use it in canning to keep fruit from browning. It's inexpensive, simple to use and surprisingly effective.