Yam

The yam is a generic name applying to several Plante S pertaining to a score of S of the Dioscorea, Dioscoréacée S, cultivated in all the tropical areas of the sphere, with a food aim, for their tubers rich in Amidon. The term indicates also the tuber itself consumed like Légume. In North America and in Quebec, what is called yam is often makes a Sweet potato of it.

Yam, which says yam in English comes from a African root nyam which means “to eat” and which one finds in several African languages: nam in wolof, yamyam in Haoussa, nyama in Zulu. For example, Peuls say " wari nyami" to say " come manger".

Principal cultivated species

  • Dioscorea alata L., winged yam or large yam;
  • Dioscorea batatas Decne., yam of China;
  • Dioscorea will bulbifera L., yam bulbifère, apple in the air or masako;
  • Dioscorea cayenensis Lam. ; yellow yam of Guinea
  • Dioscorea convolvulacea Schltdl. & Cham., yam crawling
  • Dioscorea dumetorum (Kunth) Pax, bitter or wild yam;
  • Dioscorea esculenta (Lour.) Burkill, yam of the white or small yam;
  • Dioscorea hispida Dennst., bitter thorny yam;
  • Dioscorea japonica Thunb., yam of Japan;
  • Dioscorea nummularia Lam., flattened yam;
  • Dioscorea oppositifolia L., yam Khmer;
  • Dioscorea pentaphylla L., red yam;
  • Dioscorea rotundata Poir., yam of white Guinea, it is cultivated nowadays;
  • Dioscorea trifida L.F., yam layer-layer;

Description

They are climbing plants, voluble, often dioïques. The petiolate sheets , Cordiforme S, are according to the alternate or opposite species. With their armpit bulblets develop being able to be used for the multiplication of the plant, and sometimes consumable ( Dioscorea will bulbifera ).

The inflorescences axillaires are bunches or ears; the female flowers, trimères, to ovary infère triloculaire give samares to three wings.

The tubers of variable, ovoid form with oblong, sometimes flattened or in the shape of lengthened bludgeon, can reach 1 m length and their weight, generally from 3 to 5 kg, go up to 15 kg. It are furnished with eyes like potatoes. The skin is generally yellow, but can be almost white or darker of brownish with noirâtre. the flesh is generally white, sometimes yellowish.

Composition

The chemical composition of the tubers is close to that of potatoes with approximately 25% of Amidon, but a little more Protéine S (approximately 7%, four times more than the Manioc). They are very low in fat contents and minerals, and rather rich in Vitamine C.

Certain varieties, used by the drug company, contain rather toxic substances of three types:

  • of the Alkaloid S, of which the Dioscorine which causes the paralysis of the central Nervous system (SNC),
  • of the Tanin S,
  • of the Sapogénine S, of which the Diosgénine which allows the preparation of Stéroïde S, analogues in particular of the Cortisone and of the estrogen S.

Use

The yams are an important culture with the world plan. Annual harvest is of approximately 40 million tons on 4 million hectares distributed in 56 countries. This culture nevertheless regressed in front of that of the manioc (maniota, kassav, kassava…), easier to cultivate according to the varieties, the grounds… The principal producer countries are in West Africa:

Or in Oceania (food production)

The tubers rich in starch are consumed almost exclusively in the tropical areas.

The yams are consumed cooked, braised, or fried. According to the species and varieties, the taste very variable, very pleasant, tender and is sweetened in certain cases, farinaceous food, with sweet chestnut taste generally. Certain species are (in Africa), bitter or bitter, but not truly toxic.

Production

See too

Zh-min-nan: Soaⁿ-io̍h

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