Bean is a common name for large plant seeds of several genera of the family Fabaceae (formerly Leguminosae) used for human food or animal feed.
Although "beans" usually means the seeds of bean plants, it can also mean (especially in the US) the whole young pods of bean plants, which if picked before the pods ripen and dry, can be tender enough to eat whole, whether cooked or raw. Thus the word "green beans" means "green" in the sense of unripe (many are in fact, not green in color), as the beans inside the pods of green beans are too small to comprise a significant part of the cooked fruit
The term "bean" originally referred to the seed of the broad bean, but was later expanded to include members of the genus Phaseolus, such as the common bean and the runner bean, and the related genus Vigna. The term is now applied in a general way to many other related plants such as soybeans, peas, lentils, kidney beans, chickpeas (garbanzos), vetches and lupins.
"Bean" can be used as a near-synonym of "pulse", an edible legume, though the term "pulses" is usually reserved for leguminous crops harvested for their dry grain and usually excludes crops mainly used for oil extraction (like soybeans and peanuts) or those used exclusively for sowing purposes (such as clover and alfalfa). Leguminous crops harvested green for food, such as snap peas, snow peas, etc., are classified as vegetable crops.
In English usage, the word "beans" is also sometimes used to mean the seeds or pods of plants that are not in the family Leguminosae, but which bear a superficial resemblance to true beans, for example coffee beans, castor beans and cocoa beans (which resemble bean seeds), and vanilla beans (which resemble the pods).
Some kinds of raw beans and especially red and kidney beans, contain a harmful toxin (the lectin Phytohaemagglutinin) that must be destroyed by cooking. A recommended method is to boil the beans for at least ten minutes; undercooked beans may be more toxic than raw beans. Cooking beans in a slow cooker, because of the lower temperatures often used, may not destroy toxins even though the beans do not smell or taste 'bad' (though this should not be a problem if the food reaches boiling and stays there for some time).
Fermentation is used in some parts of Africa to improve the nutritional value of beans by removing toxins. Inexpensive fermentation improves the nutritional impact of flour from dry beans and improves digestibility.
Many edible beans, including broad beans and soybeans, contain oligosaccharides (particularly Raffinose and Stachyose), a type of sugar molecule also found in cabbage. An anti-oligosaccharide enzyme is necessary to properly digest these sugar molecules. As a normal human digestive tract does not contain any anti-oligosaccharide enzymes, consumed oligosaccharides are typically digested by bacteria in the large intestine. This digestion process produces flatulence-causing gases as a byproduct. This aspect of bean digestion is the basis for the children's rhyme "Beans, Beans, the Musical Fruit."
Some species of mold produce alpha-galactosidase, an anti-oligosaccharide enzyme, which humans can take to facilitate digestion of oligosaccharides in the small intestine. This enzyme, currently sold in the U.S. under the brand-name Beano, can be added to food or consumed separately. In many cuisines beans are cooked along with natural carminatives such as anise seeds, coriander seeds and cumin.
Other strategies include soaking beans in water for several hours before mixing them with other ingredients to remove the offending sugars. Sometimes vinegar is added, but only after the beans are cooked as vinegar interferes with the beans' softening.
Fermented beans will not produce most of the intestinal problems that unfermented beans will, since bacteria can consume the offending sugars.