Plump yellow or orange tubers line the grocery aisle during the holidays, bearing the label of sweet potatoes and yams. You may be surprised to discover that sweet potatoes and yams found in the United States are all sweet potatoes (Ipomoea batatas), unless you are shopping at an ethnic store that carries true yams (Dioscorea sp.) imported from the Caribbean, says AgriLife Extension. The confusion arises from American’s need to distinguish between two types of sweet potato.
In Name Only
Sweet potatoes and true yams are entirely different plants, but the American term sweet potato and yam apply to two types of sweet potato. The white or yellow version of the sweet potato came first and carried the common name sweet potato. When producers introduced the orange sweet potato to the market, they needed a name to differentiate it from the standard sweet potato and coined it a yam. The USDA requires the additional label of sweet potato accompany these sweet tubers when labeled as yams.
Appearance and Flavor
It isn’t just the outer skin that differs when it comes to sweet potatoes. Light-skinned varieties contain yellow or white flesh, while orange sweet potatoes have deep orange flesh similar to squash. Texture also differs. The light-skinned sweet potato tends to be drier and crumbly while the orange-skinned sweet potato contains sweet, creamy flesh.
Sweet potatoes can be boiled, baked, pan fried or deep-fried to make sweet potato fries. They are also cooked in savory casseroles or made into sweet desserts, such as sweet potato pie. Because American sweet potatoes and yams are both sweet potatoes, they can be used interchangeably in recipes and require the same cooking time. Recipes that call for yams typically refer to orange sweet potatoes and may rely on their sweeter flavor and bright color.
True yams (Dioscorea Sp.) differ from sweet potatoes in several ways. They require nearly a year to mature, making them impractical for American farmers, can grow up to 5 feet in length and contain fewer vitamins and nutrients. The skin of true yams range in color from off-white to brown and the flesh may be pink, white, purple or yellow. True yams are starchier and drier than sweet potatoes.
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