The soybean (U.S.) or soya bean (UK) (Glycine max) is a species of legume native to East Asia. It is an annual plant that has been used in China for 5,000 years as a food and a component of drugs. Soy contains significant amounts of all the essential amino acids for humans, and so is a good source of protein. Soybeans are the primary ingredient in many processed foods, including dairy product substitutes.

Overview

Like some other crops of long domestication, the relationship of the modern soyabean to wild-growing species can no longer be traced with any degree of certainty. It is a cultural variety (a cultigen) with a very large number of cultivars.

The genus Glycine Willd. is divided into two subgenera (species), Glycine and Soja. The subgenus Soja(Moench) includes the cultivated soybean, G. max (L.) Merrill, and the wild soybean, G. soja Sieb.& Zucc. Both species are annual. The soybean grows only under cultivation while G. soja grows wild in China, Japan, Korea, Taiwan and Russia. Glycine soja is the wild ancestor of the soybean: the wild progenitor. At present, the subgenus Glycine consists of at least 16 wild perennial species: for example, Glycine canescens, and G. tomentella Hayata found in Australia, Europe, and Papua New Guinea.

Beans are classed as pulses whereas soybeans are classed as oilseeds. It is a versatile bean, having a diverse range of uses.

The English word soy is derived from the Japanese pronunciation of 醤油 (しょうゆ, shōyu), the Japanese word for Soya sauce; soya comes from the Dutch adaptation of the same word.

Description and physical characteristics

Soy varies in growth, habit, and height. It may grow prostrate, not higher than 20 cm (7.8 inches), or grow up to 2 meters (6.5 feet) high.

The pods, stems, and leaves are covered with fine brown or gray hairs. The leaves are trifoliolate, having 3 to 4 leaflets per leaf, and the leaflets are 615 cm (26 inches) long and 27 cm (13 inches) broad. The leaves fall before the seeds are mature. The big, inconspicuous, self-fertile flowers are borne in the axil of the leaf and are white, pink or purple.

The fruit is a hairy pod that grows in clusters of 35, each pod is 38 cm long(13 inches) and usually contains 24 (rarely more) seeds 511 mm in diameter.

Soybeans occur in various sizes, and in many hull or seed coat colors, including black, brown, blue, yellow, green and mottled. The hull of the mature bean is hard, water resistant, and protects the cotyledon and hypocotyl (or "germ") from damage. If the seed coat is cracked, the seed will not germinate. The scar, visible on the seed coat, is called the hilum (colors include black, brown, buff, gray and yellow) and at one end of the hilum is the micropyle, or small opening in the seed coat which can allow the absorption of oil.