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All About the Noble Yam

Mmmmm.  Do you know everything there is to know about the noble yam, besides that it’s delicious? Check this out from Dianne Onstad‘s Whole Foods Companion: A Guide For Adventurous Cooks, Curious Shoppers, and Lovers of Natural Foods. It’s a great gift book for the holidays, too, for all your food-lovin’ friends and family.

(Dioscorea rotundata, D. cayenensis, D. composita)

The genus name Dioscorea was given in honor of Dioscorides, a Greek physician and naturalist of the first or second century A.D. The term rotundata means “rotund” or “portly”; cayenensis means “coming from Cayenne,” the island that is the capital of French Guiana; composita means “composite.” The English name yam is of African origin, coming from the Guinean verb nyami, meaning “to eat.”

General Information
Yams are large, tuberous roots largely confined to the tropics of West Africa and Asia, although they are found in a few
other tropical regions. In the United States, yams can be grown only in the Deep South. Not to be confused with the American “yam,” which is just another name for a moist-fleshed variety of sweet potato, true yams may grow to a remarkable size, up to six feet long and more than six hundred pounds. Instead of growing underground like potatoes,
yams grow on plants and hang from plant stems. Their weight causes the stems to bend to the soil, and the yams become partially embedded like an exposed underground tuber. Every country and district that grows yams has its own particular favorite that it cultivates, harvests, and cooks. In some Pacific Islands yams are venerated as nature’s pantry, for they can be left in the ground to grow to an enormous size. Their flesh may be white, yellow, red, or even purple. Of the more than six hundred species, those most commonly encountered are brown, black-brown, or rusty tan, and all are shaggy-coated. Common types are elephant’s foot or suram, taro or dasheen, and the cocoyam, all of which look similar to enormous potatoes. The boniato looks like a sweet potato with its ruddy pink skin but has white flesh; a bit tubbier than the American sweet potato, it has flesh that is drier—more like that of a regular white potato.

In 1936 Japanese chemists formulated by partial synthesis steroidal sapogenins, primarily diosgenin, from the glycoside saponins richly found in the barbasco, a wild yam native to Mexico. By 1940 diosgenin was able to be converted into progesterone, an intermediary in cortisone production. While progesterone can be derived from diosgenin, this can only be done by a chemist in the laboratory; humans cannot produce progesterone in their bodies from yams or their extracts. In 1956 Dr. Gregory Pincus announced that he had formulated a drug that would stop ovulation and hence prevent conception. Up to that time, steroids that prevented conception had to be taken by injection, whereas it now became possible to use oral administration. Although most birth-control pills are wholly synthetic today, dioscorea still figures in their origin. Other steroid drugs derived from diosgenin include anti-inflammatory compounds such as topical hormones and systemic corticosteroids, androgens, estrogens, progestogens, and other sex-hormone combinations.

Buying Tips
Choose yams that are regularly shaped and very hard, with no cracks or soft or shrunken spots. Although they are available in many sizes, those with the best flavor weigh less than two or three pounds. Sometimes the yams will be cut open to show how moist and creamy the interior is; if not, scrape one with your fingernail to see if it is juicy. Store as you would potatoes—never in the refrigerator but rather in the potato bin or any cool, dry, dark place. Yams are most often available in Latino and Asian markets. Frequently you can buy them by the piece, according to the weight you need.

Culinary Uses
Yams have a flavor and texture much like a mealy potato—loose, coarse, dry, and rather bland. The raw flesh is crisp,
slippery, and mucilaginous. As versatile as the potato, yams can be boiled, roasted, mashed, fried, or made into casseroles; they are a perfect foil for strong, spicy vegetable mixtures. They absorb other flavors well but are enhanced by a sprinkling of sweet spice such as cinnamon, nutmeg, ground cloves, or allspice. Unlike potatoes, the skin is not
edible so should be removed. Wash under running water and then peel thickly to remove both the skin and the layer beneath. All yams contain dioscorine, which is poisonous (although cooking completely destroys it); this lies near the
peel. Cut the yam into whatever size pieces you want. If not cooking at once, keep in salted water, because yam discolors
easily. Added to soups or stews, yam’s delicate nutty flavor will sweeten the pot. Frequently it is used in place of sweet
potatoes in stews, chilies, and soups. On the islands where the boniato is a common food, people are fond of turning
it into chips, much as we do with the common potato.

Lore and Legend: It may well be that yams are worshiped because they can become awesomely huge. In the Pacific
Island of Ponape, the size of yams is described as two-man, four-man, or six-man, designating the number of men needed to lift the tuber. Tubers up to six feet long and weighing six hundred pounds have been recorded. The Trobriand Islanders build intricately decorated wooden “yam houses” where the splendid tubers are ensconced to be viewed by neighbors. In Cuba, yams are considered festival food, to be saved for special occasions.

Health Benefits
pH 5.79–6.81 (cooked). Antiarthritic, antispasmodic, diuretic, emmenagogue. The yam is hailed as a medicinal tonic for many uses, working as an agent to prevent miscarriages and to treat asthma. It also contains simple peptide substances called phytochelatins that can bind heavy metals like cadmium, copper, mercury, and lead and thus help detoxify the body. Those species of yam containing diosgenin are medicinally efficacious for fatigue, inflammation, spasms, stress, colitis, Irritable Bowel Syndrome, PMS, and menopausal complaints. The yam’s plant estrogen (phytoestrogen) seems to act as a key to unlock and potentiate existing estrogen in the body, thus eliminating or easing many of the symptoms of low estrogen.

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