Explore the fascinating world of peanuts! Learn about their unique characteristics, delightful features, and discover the countless ways peanuts are used in various culinary and industrial applications.
PEANUT, (also known as groundnut, earthnut, pistache de terre, goober, monkey nut, manilla nut, ground beans, pindars), is an annual plant grown widely in tropical and subtropical regions. The cultivated species of the peanut, Arachis hypogaea, is a member of the family Leguminosae. The peanut, a native of South America, was grown by the ancient civilizations of that continent at least 2,000 years ago. About 15 species of wild forms have been found growing in the southern areas of Paraguay and Brazil, in the northeastern area of Argentina, and throughout Uruguay.
Shortly after the discovery of South America, the peanut was introduced into Africa, Europe, and later Asia. During the 17th century of African trade, the peanut was introduced into the American colonies. The cultivation of peanuts was largely confined to Virginia until about 1865, when seeds were carried home by the soldiers of the Civil War, and the cultivation of peanuts spread throughout the southern area of the United States.
The peanut is a pea, not a nut. It belongs to the bean family, differing in that it matures its fruit or pod underground. The peanut plant may be a bush or a vine above ground which may grow to a length of 1 to 3 feet. Small yellow flowers form at the joints where the leaves are attached’ to the stems. After pollination takes place the flowers fade, and shoots are formed which elongate and enter the ground, where pods develop. The pod or shell which forms is cellulosic in nature and contains from 1 to 3 nuts or seeds when it has matured.
The shell comprises about 20 to 30 per cent of the weight of the mature peanut. The nuts or seeds are made up of three principal parts, the testa or skins, the heart or germ, and the nuts which separate into two fractions. The nuts are nutritious and contain 40 to 50 per cent of oil, 20 to 30 percent of protein, 5 to 15 per cent of carbohydrates, and other constituents.
Peanuts grow best where a loose surface of the soil can be maintained. The soil should be deeply plowed. The seeds of thick-shelled nuts should be sown about one inch deep, at intervals of about one foot, in rows about 30 to 36 inches apart, as soon as winter has passed. The whole pods of thin-shelled nuts may be sown. The surface of the soil should be kept loose and free of turf-forming grasses, until the plant is large enough to shade the ground. During harvesting, always before frost, several methods are used.
The peanut plants may be cut and dried and used for hay, and the nuts “harvested” by animals, particularly swine. Usually the whole peanut plant and root system with pods attached are “plowed out.” After a few hours, the soil is shaken off, and the plants are stacked or shocked by hand around poles about 6 to 7 feet high with crosspieces nailed to the poles about 6 to 10 inches above the ground. In warm weather, the peanuts will cure in 2 to 4 weeks. In areas of low rainfall,
the plants are “plowed out” into rows, allowed to cure, and then collected. After curing, the pods are removed from the plants by threshing. Under good cultural practice 800 to 1,000 pounds of nuts may be picked and threshed per acre, and about two tons of hay harvested per acre.
The Peanut Industry.
Peanuts are used for foods generally after processing. The oil is removed from the seeds and is used as cooking oil or in the manufacture of shortening and margarine. The residue, peanut meal or cake, is usually used for feeding livestock ; however, food-grade peanut meal may be made by special processing. Also, the protein, contained in the meal, may be isojated for food uses. After removing the cellulosic shells, oil is extracted from the seeds by one of three methods, namely, mechanical pressing (hydraulic, screw, or expeller), solvent extraction, or pressing followed by solvent extraction.
Mechanical pressing may leave more than 5 per cent of oil in the residue. In solvent extraction, the nuts are flaked, and oil is extracted by low-boiling hydrocarbons or organic solvents. Most modern processing plants use mechanical pressing to reduce the content of oil in the seeds to about 15 to 20 per cent and then solvent extraction to reduce the oil to about 1 per cent. Food-grade meals are prepared by removing the testa and hearts from the seeds and then by washing and drying the seeds. The oil is then removed from the seeds at a low temperature ; the meal is heated to improve its flavor and ground to a flour. Protein may be isolated from the meal, as follows: 1 part of meal is added to 10 parts of water. A caustic soda solution is added, until the water-meal mixture is slightly alkaline, dissolving the protein.
The insoluble fraction of the meal is separated by screening and centrifuging. The dissolved protein is recovered from the clarified solution by adding gaseous sulphur dioxide, until the solution is sufficiently acid to precipitate the greatest possible amount of peanut protein as a dense cheeselike curd. The protein curd is separated from the solution and dried at a low temperature and then used in food manufacture.
Food uses are, also, dependent on local conditions. In some countries, particularly the United States, whole roasted peanuts and salted, roasted nuts are consumed. Sizable quantities of roasted nuts are used in candies, such as chocolate and plain peanut bars, peanut brittle, and sugar-coated peanuts. Peanuts are used in some bakery products. The manufacture of peanut butter, a spread, has used as much as one third of the peanut production of the United States. When the peanuts are young and tender, they may be dug, washed, and boiled in salty water to prepare them for eating.
Feed uses for the peanut are numerous. In addition to use of the cut and dried plant as a hay, equal to soybean or cowpea hay in feeding value, peanuts may be fed as whole nuts or as processed peanut meal or cake relatively free of oil. In areas of the world where peanuts are processed for oil, the protein, contained in the meal, is a valuable source of dietary protein in mixed feeds for beef and dairy cattle, horses and mules, sheep, swine, poultry, and dogs.
Industrial uses for peanuts, particularly peanut meal and isolated protein, depend on many economic factors and are relatively small and localized. Technically, peanut-meal glues compare favorably with many commercial plywood adhesives. Peanut-meal glue is simply compounded by forming a paste of meal and water and then by adding lime, caustic soda, and other chemicals. Glues, easy to dissolve, are prepared by neutralizing the curds, formed during protein isolation, with caustic soda and then drying the. curds. These glues are suitable for making gummed tape and paper and for making flexible or nonwarping glues.
Peanut protein may also be used as the adhesive in paper coatings. Sizes for use in paper manufacture and in textile processing are prepared from peanut protein and alkaline extracts of peanut meal. A man-made fiber is made from peanut protein by dissolving the protein in a caustic soda solution forming a thick molasses-type liquid, by extruding this liquid into an acid and salt solution forming the fiber, and then by stretching, treating, and drying the fiber. The peanut protein fiber, which has been made in the United States and Great Britain, is light-cream colored in its natural state; has a soft-hand, luster, and warmth similar to that of wool.