The Science of Potatoes
So versatile, and such a perfect accompaniment to meat. Such comfortable food.
Despite what you might have heard, potatoes are not from Ireland. Scientists believe they come from the Lake Titicaca, Peru, area, at about 12,500 feet above sea level, where they were first cultivated by Inca Indians 8,000 years ago. The International Potato Center in Lima, founded in 1971, maintains the world's largest collection of potato seeds: More than 4,500. Spanish conquistadors brought them back to Europe in the 1500s and today they are the world's fouth most important food source, after wheat, corn, and rice, according to William Roca, a geneticist at the Center.
They grow underground, bulbous parts of the plant's roots called tubers. The flesh is usually white, but it can also be yellowish, purple, or even red. The skin is not only the familiar tan and brown, but red, purple, blue, pink with yellow spots, and yellow with pink spots, and it gets thicker with age. Loaded with starch and sugars, they get sweeter with age. The skin is usually edible if washed thoroughly, and it should be eaten because many of the nutrients are in the skins or just under them.
The three categories of potatoes
For cooking purposes, potatoes can be divided into three categories:
- Starchy potatoes. These are low in moisture and high in starch, and they are especially good for baking, mashing, frying, and roasting, but they are not very good for boiling because they can disintegrate if boiled too long. When they are cooked their texture is dry and floury. Most common is the Russet Burbank from Idaho. King Edward is another common variety.
- Waxy potatoes. These are good, all-purpose spuds because they have moderate moisture and starch. When boiled they get soft around the edges but hold their shape, making them especially good for potato salads and casseroles. Most red-skinned potatoes are waxy. Yukon Gold is a popular example.
- New potatoes. These are young spuds harvested in late winter and early spring. They are usually small, about golf ball size, thin skinned, and low in moisture and starch. They are best for boiling, skin and all. Use these in stews, soups, or boiled, buttered, and sprinkled with parsley or your favorite herb. Many of the fingerling potatoes are new potatoes.
The all-purpose potato. All this understood, there is one potato that comes close to being the all-purpose spud, good for practically any use, it's the Yukon Gold, developed in 1960s at University of Guelph in Canada and released to the public in 1980. In addition to its versatility under a variety of cooking conditions, it has a winning mild buttery flavor.
Buying and handling potatoes
Buying potatoes. Try to buy potatoes individually rather than by the bag so you can inspect them. When selecting potatoes, try to pick those that are firm, without sprouts, and with no bruises, scars, or green patches. Greenish potatoes can have a mild toxin, solanine, but in such minute amounts there is nothing to worry about. To be safe, discard any potatoes that have green patches.
Storing potatoes. Potatoes should be stored in the cool and dark, but not frozen. Ideal storage temp is 40-45°F at 95% humidity. Root cellars and crawl spaces are good. In the fridge the starches turn to sugar quicker, and the cold can also darken the meat. Potatoes and onions go together well on the dinner plate, but not in storage. They each emit a gas that can spoil the other. Put them in paper bags, not plastic bags. The need to breathe or they can rot.
Quality control. After you wash them or peel them, sniff them! If they smell moldy or musty, throw them out.
Cleaning potatoes. Potatoes grow underground and come out of the ground covered in dirt. They are cleaned before sold, but there can still be a bit of dirt and microbial contamination, so they need to be scrubbed vigorously. Most cookbooks recommend a brush, but I prefer a scrubby sponge that has no residual soap in it. If you plan to eat the skin, cut out the bad spots, but you can leave in the eyes. Sniff them carefully and discard any that smell musty.