Introduction
(Leguminosae or Fabaceae)
With some 700 genera and about 18,000 species, legumes are the third largest order of flowering plants. Despite the large number of species available, only about twenty-two are grown in any quantity for human consumption. Legumes are broadly classified as beans, peas, and lentils. However, legumes include such other foods as alfalfa, carob, and peanuts. Legumes are also characterized by seed-bearing pods, with the seeds themselves inside. If the fresh pods are eaten, they are known as legumes; but, if the seeds are removed from the pod and eaten, they become known as pulses. These pulses can be eaten fresh, dried, frozen, or canned.
Legumes are found in the temperate latitudes, humid tropics, dry regions, savannas, and mountain ranges. While the soybean needs warmth, pigeon peas prefer the heat and humidity of the tropic. The haricot bean thrives in Mediterranean climates, while the hardy butter bean tolerates colder latitudes. Legumes are extremely varied in appearance -- round, flat, winged, long, short, thick, thin, straight, curved, papery, leathery, woody, or fleshy. Their size can range from that of a pinhead to those over three feet long. Generally speaking, their pods burst open lengthwise at one or both ends when ripe, releasing the seeds, which are the actual fruits. The protein content of legumes is almost three times that found in grains.
Since legumes are low in methionine and high in lysine and essential amino acids, they make a perfect companion for grains, which are the opposite, high in methionine and low in lysine.
Well over 150 million tons of legumes are cultivated worldwide each year, with the majority grown in home gardens and on small commercial farms. Next to soybeans and peanuts, from which oil is commercially extracted, beans are in the forefront internationally. These legumes are the most important sources of protein for the poor rural populations of Africa, Asia, and South America, and should be for the more affluent as well.
Legumes in India are called dhal/dal, and are vital to some 600 million vegetarians in that country. Next to peas, many varieties of beans and lentils supply the inhabitants of this huge country with their desperately needed protein. Eaten together with rice or bread, spicy bean and lentil curries provide the ideal combinations of nutrients in the form of good-quality protein, carbohydrates, and dietary fiber. In India and South America, their way of preparing legumes with a variety of seasonings and spices is not only exemplary from a culinary standpoint, but also helps the body cope with the hard to digest seeds of the legume. Spices stimulate the flow of digestive juices, alleviating the unpleasant consequences of the indigestible carbohydrate stachyose that is found in beans and lentils. Both Indian and Western cooks are aware of a second way of reducing the undesireable side effect of gas after eating beans and lentils: that is hulling them. Although the starchy seeds disintegrate very quickly, their hulls do not.
Although legumes are an important staple for millions of people, several toxic substances occur in kidney beans, garbanzo beans, peas, lentils, among others. They can all be rendered harmless by soaking and vigorous boiling. Phytic acid is also found in such foods as legumes, seeds, and grains. Phytic acid, or inositol hexaphosphate, is a form of inositol, considered by many to be a B vitamin but has the tendency to bind minerals including calcium, magnesium, iron, and zinc preventing their absorption in the body. Thus in order to prevent this from happening, such foods must have this substance deactivated through leavening, baking, or sprouting. These are the reasons that legumes should never be eaten raw.
Legumes are divided into three main families, with a fourth that includes some unusual ones.
These are as follows:
Old World Legumes:
-- Beans which also include favas and chickpeas
-- Peas which include starchy peas and sweet peas, as well as lupini
-- Lentils
New World Legumes:
-- Phaseolus family, which consists of common and true beans of more than 4,000 varieties, some of which have now been assigned to the genus Vigna.
-- Peanuts
Asian and African Legumes:
-- Asian: many Vigna species and soybeans (more than 1000 varieties)
-- African: cowpeas, yardlong beans, black-eyed peas, pigeon peas (many varieties)
Unusual legumes include: winged beans, yam beans, purple hyacinths, goober peas.
