Despite their resemblance to yams, sweet potatoes are entirely unrelated. The large, orange-fleshed roots are members of the morning glory family (Ipomoea batatas), and in fact, they're not potatoes at all.
In many parts of the United States, sweet potatoes are only served at holiday time, and even then, smothered with marshmallows. But in other cultures and cuisines, these modest-looking vegetables are a prominent part of the everyday diet. In Japan, South America and even the southern United States, they're a kitchen cupboard staple, adding vibrant color and nutrition to soups, salads, pies, fries, biscuits, tempura and sushi.
Native to Central America, the Incas and the Mayas called sweet potato vines cassiri. They grew many different varieties, including one used by artists as a coloring agent.
There are many varieties of sweet potatoes, but the two most commonly grown can be described as either pale-skinned or dark-skinned. Pale-skinned sweet potatoes have thin, light yellow skins and pale yellow flesh. They are not sweet after cooking and their texture is dry and crumbly, similar to a white baking potato. Dark-skinned sweet potatoes (often confused with yams) have thicker, dark orange skins and sweet, orange flesh that cooks to a much moister texture.
Though harvested in the late fall, modern cultivating and storage techniques are helping to make sweet potatoes available year-round. Canned and frozen potatoes are also available year-round and sometimes labeled as yams.
When buying, choose firm, evenly shaped sweet potatoes with no cracks, bruises or signs of decay. For the most nutrition value, always select those with the deepest orange color.
At home, store sweet potatoes in a cool, dry, well-ventilated container. Your basement in the summer, or your garage in the winter is best. Do not store uncooked sweet potatoes in the refrigerator. The too-cold temperature alters their flavor and produces hard, woody center cores.
For the best flavor and freshness, use your sweet potatoes within a week or two after purchase. Once cooked, sweet potatoes can be stored in the refrigerator for up to a week. Cooked sweet potatoes also freeze well in aluminum foil or freezer wrap.
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