Only a few other foods are as nutritious, delicious, and versatile as the potato. Not only does a potato give you an energising supply of complex carbohydrates, but it also provides protein and important vitamins and minerals, including potassium, vitamins B6 and C, copper, and manganese. For a substantial helping of fibre, eat potatoes with the skin. The world of potatoes divides into so-called waxy potatoes, starchy potatoes, and all-purpose potatoes. Waxy potatoes are better for boiling, starchy for baking, and all-purpose falls somewhere between the two

In addition, potatoes can be differentiated according to age. They may be sold soon after they are dug ("new" potatoes) or kept in cold storage for up to a year before sale. Only potatoes that are freshly harvested may be called "new." Many consumers believe that "new" simply denotes a small, round red or white potato, but true new potatoes have thin "feathering" skins that can be brushed off with your fingers. Mature potatoes, by contrast, have thick skins. True new potatoes, which are freshly dug potatoes, may be as small as marbles or full-sized. They have a high moisture and sugar content, so they cook quickly and have a delicately sweet flavour.

Buying
If possible, choose individual potatoes from a bulk display. Buy a large bag only if you can check the condition of the potatoes through the packaging, and if you are going to use them before they spoil. Look for clean, smooth, well-shaped potatoes. Potatoes should feel firm, the "eyes" the buds from which sprouts can grow few and shallow, and the skins free of cracks, wrinkles, or dampness. Reject potatoes with black spots, bruises, or other discolorations. Reject potatoes with a green tinge to the skin: This is an indication that solanine a naturally occuring toxin is present, a result of a potato's exposure to the sun . Also reject potatoes that are sprouting a sprouting potato, though edible, has started to age and may contain increased amounts of solanine.

Storage
Few modern homes have cellars, but a cool (45ºF to 50ºF), dark, dry place makes the best storage area, as warmth and moisture encourage sprouting, and direct sunlight can cause the potato skin to form a toxin called solanine. Don't put potatoes in the refrigerator, or store them at temperatures below 45°F. Their starch will turn to sugar, giving them an undesirable sweet taste (although leaving them at room temperature for a few days allows the sugar to turn back into starch). Keep the potatoes in a brown paper, or perforated plastic bag. Check them occasionally and remove any that have sprouted, softened, or shriveled; a bad one can adversely affect the condition of the others.

Mature potatoes will keep for up to two months under optimum conditions; new potatoes are more perishable and should be used within a week of purchase. Don't wash potatoes before storing, or they will spoil more quickly. And don't store onions together with potatoes: The gases given off by onions accelerate the decay of potatoes, and vice versa. Neither raw nor most cooked potatoes freeze well; however, mashed potatoes may be packed into containers and frozen.

Preparation
Nutritionally speaking, the less you do to potatoes, the better. The skin is an excellent source of fibre , so try to leave it on. But if you decide to peel it because you don't like the taste of the skin, do so carefully. Use a swivel bladed vegetable peeler to remove the thinnest possible layer, and thus preserve the nutrients just below the skin. Better yet, simply scrub unpeeled potatoes under cold water before cooking; remove any sprouts, green spots, or deep eyes with a sharp paring knife.

Generally speaking, low-starch, high-moisture "waxy" potatoes, such as round reds, are best for boiling or steaming. They remain firm textured when sliced or diced (before or after cooking), and are therefore a good choice for stews, casseroles, or salads in which you want the potato pieces to hold their shape. Starchy potatoes have a drier flesh. They turn out fluffy when baked or mashed and may fall apart if cut into chunks or slices after cooking. They are best used in soups and stews in which the potatoes are meant to break up and thicken the cooking liquid. All purpose potatoes are sort of a compromise potato, neither too starchy nor too waxy.

Potatoes occasionally turn grey or dark after they are boiled; this colour change may be caused by the conditions under which they were grown or stored. It's impossible to tell which potatoes will turn dark, but the discoloration does not affect flavour, texture, or nutritional value. Contact with aluminum or iron will also discolour potatoes, so cook them in stainless steel pots. For the same reason, raw potatoes should not be cut with a carbon steel (non stainless) knife. If exposed to air, peeled raw potatoes will also discolour. Cook the potatoes immediately in a pan of water that has already been brought to a boil. And if you are interrupted while preparing them, place them in a bowl of cold water, then add a few drops of lemon juice or vinegar. This trick will help to keep the potatoes white.