Legumes are members of the bean family, which includes all types of beans and peas as well as soybeans, peanuts, alfalfa, and clover. This diverse and widely distributed plant family also includes trees and ornamental such as black locust, wisteria, lupine, and the Texas bluebonnet.
The seeds of many legumes are an important food source worldwide. They are so rich in both oil and protein and so inexpensive that they are often called “poor man’s meat.” The high protein content of legumes is associated with nodules of nitrogen-fixing bacteria that form on their roots. These bacteria are able to convert free atmospheric nitrogen into a form that can be used by plants in the making of proteins and other nitrogen compounds.
Because of these nitrogen-fixing bacteria, the cultivation of legumes enriches the soil. For this reason, farmers often rotate legumes with crops that deplete soil nitrogen. Soybeans are often rotated with corn in the central United States.
Sometimes leguminous crops may be plowed under as a “green manure” instead of harvested. Such practice was more common before the advent of chemical fertilizers, but may gain renewed importance as chemical fertilizers have serious environmental drawbacks and many developing nations cannot afford the expense of these chemicals to begin with.
The agriculturally important legumes are: beans and peas, peanuts, and soybeans.
Beans and Peas – King of the Legumes
There is great diversity inherent in the term bean as there are hundreds of varieties of this old and common food crop. Beans come in all sizes, shapes, and colors: kidney beans, lima beans, pinto beans, navy beans, green beans, wax beans, and butter beans being the most familiar to us in the United States.
Beans are an excellent source of protein averaging 25% and while the dry seeds were considered the only edible part of thousands of years, today popular varieties such as green beans and wax beans are eaten pod and all.
The term pea also denotes dozens of different kinds of edible seeds and, in some cases, entire pods. Most familiar are green peas, split peas, black-eyed peas, lentils, chick-pea (or garbanzos), and snow peas. Nutritionally peas are also a good source of protein averaging around 21%.
Peanuts – Goobers Taste Great!
In the sixteenth century Spanish explorers discovered peanuts growing in South America and introduced the world to them. Whether you call them peanuts, goobers, or groundnuts, you are discussing one of nature’s most unusual plants. After pollination, the flower stalk elongates downward pushing the developing fruit into the soil. Underground the fruit matures into a dry pod with two seeds (peanuts) inside. Harvesting consists of digging up these pods.
The peanut is highly nutritious with 45%-50% oil and 25%-30% protein and without question one of the America’s favorite foods with over one billion pounds of whole peanuts, candy, and peanut butter consumed per year. Half of the U.S. crop is used to make just peanut butter. (Peanut butter was originally developed by a St. Louis physician in the 1890s as a nutritious and easily digested food for invalids who had trouble chewing.)
Peanut oil is found in margarine, shortening, salad dressing, cooking oil, in some soaps, and in a variety of cosmetics and industrial products such as plastics and paints.
Soybeans – Protein Galore
Highly regarded in the Orient for centuries, soybeans are relatively new to the West. When first introduced into North America in 1804, they were considered an oddity and not really planted as a crop until the 1920s. Since then, soybean production has increased dramatically, making the United States the world’s leading producer today.
Soybeans are among the most nutritious plant foods known, containing 13%-25% oil and more protein (30%-50%) than lean beef. Originally used only as animal food, soy protein is becoming increasingly important in the human diet. After the oil is extracted, the soy meal that remains can be mixed with wheat flour in a variety of breads, pasta, and breakfast foods.
Another use is in textured vegetable protein (TVP). By spinning the soy protein into long fibers and adding artificial flavors and colors, TVP can be made into cholesterol-free imitation meats. Imitation bacon bits are also made in this manner.
Soy oil is used so extensively as cooking oil, salad oil, and in margarine, shortening, and salad dressing that the average American consumes almost 6 gallons of it per year. Industrially, soy oil is used in the manufacture of paints, inks, soaps, insecticides, and cosmetics.
A fat called lecithin extracted from soybeans is added to cake mixes, instant beverages, whipped toppings, and salad dressing to stabilize them and to extend their shelf life.
Other less well known legumes are useful as animal forage, spices, fast-growing sources of wood, laxatives, charcoal and even jewelry.
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