Do you think of sweet potatoes only as a delicious and nutritious vegetable? George Washington Carver begged to differ. While most well known for his peanut research, the American botanist and inventor also developed over 100 products using sweet potatoes, including sizing for cotton fabrics and a glue for postage stamps.
The recent resurgence in popularity of the sweet potato is thanks to its taste and nutritive value, rather than its manufacturing uses. In 2000, each American ate an average of 4.2 pounds of sweet potatoes. In 2014, we increased consumption almost 80 percent, to 7.5 pounds that year. Still a far cry from the 1943 number of 21.7 pounds, but on the upswing nonetheless.
Sweet potato cultivation dates back to prehistoric Peru. In the United States, they were grown by Native Americans, followed by colonists throughout the southern states. The residents of Benton, Kentucky, are long-time fans; they've been honoring the sweet potato in their Tater Day Festival—complete with parade, carnival, canning and cooking competitions—since 1843.
Though the terms are often used interchangeably, the sweet potato and yam are two entirely different plants. Sweet potatoes, with their smooth, thin skin, are in the morning glory family while rough, scaly yams are related to lilies. The yam has drier, starchy flesh, while the sweet potato is, well, sweeter and moister. And sweet potatoes are generally grown in the U.S., while yams are imported from tropical areas.
Just to confuse matters, "yam" is also sometimes used for sweet potatoes that are grown in Louisiana, where growers dubbed the orange varieties they adopted from Puerto Rico "yams" to distinguish them from other sweet potatoes grown in the States. Take note to be in the know: The "yams" you see in the produce aisle are more likely sweet potatoes.
Rated by The Center for Science in the Public Interest as the most nutritious vegetable, sweet potatoes are high in vitamins A and C and antioxidants, an excellent source of potassium and a good source of dietary fiber.
The yellow/orange-fleshed varieties are highest in beta-carotene (an antioxidant that converts to vitamin A in the body), and the purple-fleshed varieties are high in anthocyanins (another antioxidant). By the way, the deeper the orange flesh color, the richer the beta-carotene content. Despite its name, the sweet potato has a low glycemic index.
For maximum nutrition, eat the skin as well as the flesh, unless the potatoes have been waxed, in which case you may want to peel them. (Sweet potatoes and some other fruits and vegetables are sometimes waxed to improve shelf life and make them more "attractive." They should be labeled as such. These wax coatings meet FDA food additive regulations for safety, but you may prefer to avoid them.)
There are three types of common sweet potatoes: orange, white and purple. Orange varieties include Jewel (the most commonly sold commercial variety), Garnet, Beauregard, Covington, California Gold, Carolina Ruby, Evangeline and Hernandez. Those with purple flesh include Agena, Japanese Purple, Korean Purple and Mokuau. White flesh varieties include Murasake, Oriental and O'Henry. For a descriptive chart of sweet potato varieties, visit the North Carolina Sweet Potato Commission website.
There are also dry-fleshed or firm sweet potatoes, often used in Asian and East Indian cooking. Varieties of dry sweet potatoes include Kotobuki, Okinawa, Yellow Jersey and Hanna.
The nutty, creamy taste of sweet potatoes shines in both sweet and savory dishes. You'll find them in gratins and other casseroles, soups and stews, salads, curries, quick breads, pies, cookies and cakes.
Bake sweet potatoes whole (like baking potatoes), slice in half, and top with scallions, sour cream, crumbled bacon or sautéed mushrooms for a new version of an old favorite; or try Black Bean–Smothered Sweet Potatoes, seasoned with cumin and coriander.
Spicy Sweet Potato Wedges with Jalapeño Sour Cream make a perfect side for burgers or hefty sandwiches, and easy-to-prepare (but luscious and pretty) Maple-Cranberry Sweet Potatoes will wow as a side to turkey.
For updated comfort, combine sweet potatoes with coconut milk, maple syrup, nutmeg and pecans in this Sweet Potato Casserole. Instead of the usual scalloped potatoes, try Sweet Potato and Greens Gratin, featuring kale or Swiss chard, Parmesan and lively seasonings.
For an ethnic treat, Sweet Potato Maafe is a vegetarian version of a popular West African dish, with a robust peanut and tomato sauce that's traditionally served over rice or couscous.
Sweet Potato Bread is richly flavored and deeply colored. Serve it warm with honey cream cheese and your favorite tea. And the next time the occasion calls for pie, try this fun Sweet Potato Upside Down Pie with a pecan bottom. . . er, top.
Luckily, sweet potatoes are available year round, though peak season is September through December. Look for specimens with even coloration, free of cracks, bruises and soft spots. Note that small to medium specimens are often less starchy than larger ones. (Lower starch means lower carbohydrate content and also makes for better crispy potatoes, as for fries, hash browns or chips. Higher starch content results in a fluffier, softer texture, which you may prefer for mashing.)
Store sweet potatoes in a dry bin (not in the refrigerator) for up to two weeks. Before cooking, scrub the skin and trim any bruised or woody pieces. Use a stainless steel knife when cutting because carbon will darken the flesh.
Read chef and cookbook author Deborah Madison's take on Sweet Potatoes.