Yam (vegetable)

Yams are perennial herbaceous vines native to Africa, Asia, and the Americas and cultivated for the consumption of their starchy tubers in many temperate and tropical regions.

The tubers themselves, also called "yams", come in a variety of forms owing to numerous cultivars and related species.

The majority, or meat, of the vegetable is composed of a much softer substance ranging in color from white or yellow to purple or pink in mature yams.

[1] Three species were independently domesticated on those continents: D. rotundata (Africa), D. alata (Asia), and D. trifida (South America).

[1] Yams are cultivated for the consumption of their starchy tubers in many temperate and tropical regions, especially in West Africa, South America and the Caribbean, Asia, and Oceania.

Yam crops face pressure from a range of insect pests and fungal and viral diseases, as well as nematodes.

For maximum yield, the yams require a humid tropical environment, with an annual rainfall over 1,500 millimetres (59 in) distributed uniformly throughout the growing season.

White, yellow, and water yams typically produce a single large tuber per year, generally weighing 5 to 10 kilograms (11 to 22 pounds).

It looks similar to the white yam in outer appearance; its tuber skin is usually a bit firmer and less extensively grooved.

It was introduced to Europe in the 19th century, when the potato crop there was falling victim to disease, and is still grown in France for the Asian food market.

Because of the small size of the tubers, mechanical cultivation is possible, which along with its easy preparation and good flavor, could help the lesser yam to become more popular in the future.

In Asia, detoxification methods, involving water extraction, fermentation, and roasting of the grated tuber, are used for bitter cultivars of this yam.

The bitter compounds in yams also known locally as air potato include diosbulbin and possibly saponins, such as diosgenin.

[35] But raw yam has the highest potassium levels amongst the 10 major staple foods of the world (see nutritional chart).

Yam generally has a lower glycemic index, about 54% of glucose per 150 gram serving, compared to potato products.

Experts emphasize the need to supplement a yam-dominant diet with more protein-rich foods to support healthy growth in children.

When stored, they continue to respire, which results in the oxidation of the starch (a polymer of glucose) contained in the cells of the tuber, which converts it into water, carbon dioxide, and heat energy.

[44] Among the Akan of Ghana, boiled yam can be mashed with palm oil into eto in a similar manner to the plantain dish matoke, and is served with eggs.

The powder can be mixed with boiling water to create a thick starchy paste, a kind of pudding known as amala, which is then eaten with local soups and sauces.

Some varieties of these tubers can be stored up to six months without refrigeration, which makes them a valuable resource for the yearly period of food scarcity at the beginning of the wet season.

[1] Yam is the main staple crop of the Igbos in south eastern Nigeria where for centuries it played a dominant role in both their agricultural and cultural life.

[citation needed] Yams are particularly consumed in the coastal area of the Northeast region, although they can be found in other parts of the country.

In 2010, Colombia was among the 12 countries with the highest yam production worldwide, and ranked first in yield of tons per hectare planted.

White- and off-white-fleshed yams are cut in cubes, cooked, lightly fermented, and eaten as afternoon snacks.

[citation needed] An exception to the cooking rule is the mountain yam (Dioscorea polystachya), known as nagaimo and can be further classified into ichōimo (lit.

[citation needed] Mountain yam is eaten raw and grated, after only a relatively minimal preparation: the whole tubers are briefly soaked in a vinegar-water solution to neutralize irritant oxalate crystals found in their skin.

The raw vegetable is starchy and bland, mucilaginous when grated, and may be eaten plain as a side dish, or added to noodles.

[citation needed] In central parts of India, the yam is prepared by being finely sliced, seasoned with spices, and deep fried.

[citation needed] Yam is, along with cassava and taro, a staple food, and is consumed boiled, roasted in a lovo, or steamed with fish or meat in curry sauce or coconut milk and served with rice.

[citation needed] The New Yam Festival celebrates the main agricultural crop of the Igbos, Idomas, and Tivs.