A weeknight gratin or homemade mash is possible if you peel the potatoes in advance. Peeling potatoes a day ahead of a big party at which you're serving potato salad or fries can also help you minimize last-minute prep. But, once peeled, potatoes' color changes from white to an unpleasant pinkish gray. A bowl of water offers a quick fix for this problem.
When you cut into the flesh of a potato, you breaking down the vegetable's cell walls -- exposing phenols and enzymes to the air. These compounds react with oxygen to create a chemical reaction that causes them to change color. The result is the pink or grey discoloration of the potato. Potatoes that have changed color aren't dangerous to eat, they're just not too appetizing.
Soak the Taters
A simple way to prevent oxygen from turning your potatoes an unsightly color is to place the cut pieces into a bowl of cold water. The potatoes must be completely submerged, though -- any bit not covered may turn gray, so use a sufficiently deep dish and enough water to cover. The water reduces the cut potatoes' contact with oxygen, so discoloration takes place far more slowly. Place this bowl of submerged potatoes in a refrigerator for up to 24 hours. After this time, the potatoes' quality and color will start to deteriorate.
Add a Little Acid
Add a small amount of acid to the water to further discourage discoloration. For every gallon of water, just a tablespoon of lemon juice or vinegar is enough. This amount of acid won't affect the final taste of your potatoes, but it could make them extra crispy if you plan to roast or fry them.
Using Your Potatoes
Even if you're boiling the potatoes, drain them first. Starch accumulates in the soaking liquid overnight and it could contribute to gummy potatoes -- especially if you plan to mash them. For fried potatoes, hash browns or roast potatoes, dry soaked potatoes thoroughly before using to prevent them from steaming as they cook. Dry potatoes will form a delectable crunchy exterior with a soft, fluffy interior.