Real Food Encyclopedia | Yams
That bright platter of sticky-sweet candied “yams” — a long-treasured part of the Thanksgiving meal — is often not. Sweet potatoes are often colloquially referred to as “yams,” and not just on Thanksgiving. True yams (Dioscorea alata) are biologically distant from sweet potatoes, although they are both tubers. Some people further insist that the redder, sweeter and more elongated Japanese varieties of sweet potatoes are “yams” while the paler, rounder, supermarket staple are sweet potatoes. In any case, you are unlikely to find yams in a conventional U.S. grocery.
What are yams, then? And what sets them apart from the familiar, orange-fleshed winter vegetable we so often confuse them with? Read below to learn more.
Fun facts about yams:
- Yams can vary in size from that of an average potato to over 100 pounds.
- In some West African languages, the word “yam” means “to eat.”
- African countries were responsible for 96 percent of worldwide yam production as of 2007.
- The interior flesh of yam varieties can range in color from white to yellow to bright purple (as can those of sweet potatoes, adding to the confusion).
- In Ghana, yams are traditionally served to celebrate the arrival of a new baby.
What to look for when buying yams
Yams are distinct from other tubers like potatoes for their hairy, rough surface. Most varieties have a more tube-like shape and they can grow quite long and fibrous if not harvested on time. Its flesh is typically starchier and less sweet than sweet potatoes, and can be ground into starches and flours. Yams are seldom eaten raw, except as grated fresh mountain yam, and have a mildly sweet flavor. They are extremely versatile and varied plants, having unique culinary associations throughout the world. However, like potatoes, they are most commonly eaten by boiling, baking or roasting.
Sustainability of yams
Requiring about one year and plenty of water to grow, yams are highly susceptible to pest, fungus and diseases. Infected plants have been known to wipe out entire crops in recent years. As a result, many studies have been undergone to understand and manage yam healthiness. Another contributing factor to crop failure lies in the storage of yams after harvest: Diseases like dry rot can easily destroy yams post-harvest if they are not properly stored and handled. To counteract these threats, yam crops have been treated to a number of chemical pesticides during propagation, growth and post-harvest. It can be difficult to locate or determine non-chemically treated yams in the market in the United States.
As a perennial plant, yams can be cultivated at any time of year, but they are often treated as an annual crop. In West Africa, yams are commonly planted at the beginning of the warm, rainy season and harvested in early autumn of the next one. Peoples such as the Ashanti and Igbo celebrate the harvest of yams with an annual celebration lasting days. Other yams like the mountain yam are winter crops that are planted at the beginning of the cold season and harvested the following autumn or winter.
Yams are a staple crop of West Africa, and have been grown there for 11,000 years. Anthropologists have dated grinding stones from Africa that may have been used to pound starchy yams back to over 100,000 years ago in the Middle Stone Age. Slave traders who arrived in West Africa may have brought yams back to the Americas during their journeys. But once African slaves were in North America, they found sweet potatoes, native to the New World, as apt substitutes for yams.
Conversely, types of yams referred to as “mountain yams” have been eaten in Asia for thousands of years as well. Often found in Chinese herbal medicine, today one of the most popular Asian mountain yams is called naga-imo in Japanese. Another popular variety is known as ubi or purple yam, the tubers of flowering water vines eaten throughout Southeast Asia.
Yams are traditionally stored in cool, dark earthen pits before being shipped to market. When you purchase yams, choose ones that are not bruised, visually blemished or discolored, and store for up to two weeks in a cool, airy dark place. If stored too long, they may begin to sprout (like other tubers). They are not recommended for refrigeration or for keeping covered in plastic to discourage rot or the growth of mold.
Yams can be prepared much like potatoes or sweet potatoes — even deep-fried in wedges like French fries. In addition to boiling, roasting or baking them, they can be mashed or pounded into thick soups or porridges, such as the traditional fufu or African porridge. They can be fried and served with a spicy dipping sauce, like the Nigerian dundu. When not used for medicine or for grating onto dishes, mountain yams can be sliced thinly and dressed for a salad. And of course, they can be baked in casseroles with a sweet glaze, such as with candied yams.
Yams are primarily eaten as a source of carbohydrates, but they provide many health benefits in addition to filling one’s belly. They are high in fiber, Vitamin C, Vitamin B complex and potassium. Unlike sweet potatoes, however, they are not a major source of Vitamin A. Yams are also associated with intestinal health thanks to their high fiber content. Traditional Chinese medicine has long used yams to treat stomach conditions such as indigestion and poor appetite, and for kidney and spleen health.