soybean, (Glycine max), also called soja bean or soya bean, annual legume of the pea family (Fabaceae) and its edible seed. The soybean is economically the most important bean in the world, providing vegetable protein for millions of people and ingredients for hundreds of chemical products.

Domestication and history

The origins of the soybean plant are obscure, but many botanists believe it was first domesticated in central China as early as 7000 BCE. An ancient crop, the soybean has been used in China, Japan, and Korea for thousands of years as a food and a component of medicines. Soybeans were introduced into the United States in 1804 and became particularly important in the South and Midwest in the mid-20th century. Brazil and Argentina are also major producers.

Physical description and cultivation

The soybean is an erect branching plant and can reach more than 2 metres (6.5 feet) in height. The self-fertilizing flowers are white or a shade of purple. Seeds can be yellow, green, brown, black, or bicoloured, though most commercial varieties have brown or tan seeds, with one to four seeds per pod.

In the United States the majority of soybean crops are genetically modified for resistance to the herbicide glyphosate. The soybean may be cultivated in most types of soil, but it thrives in warm, fertile, well-drained, sandy loam. The crop is planted after all danger of frost is past. Soybeans are usually harvested mechanically, after the leaves have fallen off the plant and the moisture content of the seed has dropped to 13 percent, permitting safe storage. Like other legumes, the plant adds nitrogen to the soil by means of nitrogen-fixing bacteria and historically has been an important soil-enriching crop, though this practice is not common in most industrial agriculture systems.

Uses

The soybean is one of the richest and cheapest sources of protein and is a staple in the diets of people and animals in numerous parts of the world. The seed contains 17 percent oil and 63 percent meal, 50 percent of which is protein. Because soybeans contain no starch, they are a good source of protein for diabetics.

In East Asia and elsewhere, the bean is extensively consumed in the forms of soy milk, a whitish liquid suspension, and tofu, a curd somewhat resembling cottage cheese. Soy sauce, a salty brown liquid, is produced from crushed soybeans and wheat that undergo yeast fermentation in salt water for six months to a year or more; it is a ubiquitous ingredient in Asian cooking. Other fermented soy foods include tempeh, miso, and fermented bean paste.

Soybeans are also sprouted for use as a salad ingredient or as a vegetable and may be eaten roasted as a snack food. Young soybeans, known as edamame, are commonly steamed or boiled and eaten directly from the pod.

Modern research has led to a remarkable variety of uses for the soybean. Its oil can be processed into margarine, shortening, and vegetarian and vegan cheeses. Soybean meal serves as a high-protein meat substitute in many food products, including baby foods and vegetarian foods, and can be imparted with a meatlike texture for increasing the cooked yield of ground meats. Industrially, the oil is used as an ingredient in paints, adhesives, fertilizers, sizing for cloth, linoleum backing, and fire-extinguisher fluids, among other products.