Peanut
The peanut, also known as the groundnut, goober, goober pea, pindar or monkey nut, is a legume crop grown mainly for its edible seeds, contained in underground pods. It is widely grown in the tropics and subtropics by small and large commercial producers, both as a grain legume and as an oil crop. Geocarpy is atypical among legumes, which led botanist Carl Linnaeus to name the species hypogaea, from Greek 'under the earth'.
The peanut belongs to the botanical family Fabaceae, commonly known as the legume, bean, or pea family. Like most other legumes, peanuts harbor symbiotic nitrogen-fixing bacteria in root nodules, which improve soil fertility, making them valuable in crop rotations.
Despite not meeting the botanical definition of a nut as "a fruit whose ovary wall becomes hard at maturity", peanuts are usually categorized as nuts for culinary purposes and in common English. Some people are allergic to peanuts and can have a potentially fatal reaction; this is distinct from tree nut allergies.
Peanuts are similar in taste and nutritional profile to tree nuts such as walnuts and almonds, and, as a culinary nut, are often served in similar ways in Western cuisines.
Botanical description
The peanut is an annual herbaceous plant growing tall. As a legume, it belongs to the botanical family Fabaceae, also known as Leguminosae, and commonly known as the legume, bean, or pea family. Like most other legumes, peanuts harbor symbiotic nitrogen-fixing bacteria in their root nodules.The leaves are opposite and pinnate with four leaflets ; each leaflet is long and across. Like those of many other legumes, the leaves are nyctinastic; that is, they have "sleep" movements, closing at night.
The flowers are across, and yellowish orange with reddish veining. They are borne in axillary clusters on the stems above ground and last for just one day. The ovary is located at the base of what appears to be the flower stem but is a highly elongated floral cup.
Peanut fruits develop underground, an unusual feature known as geocarpy. After fertilization, a short stalk at the base of the ovary—often termed a gynophore, but which appears to be part of the ovary—elongates to form a thread-like structure known as a "peg". This peg grows into the soil, allowing the fruit to develop underground. These pods, technically called legumes, are long, normally containing one to four seeds. The shell of the peanut fruit consists primarily of a mesocarp with several large veins traversing its length.File:Peanut plumule and radicle.jpg|thumb|Peanut seed separated showing the cotyledon, plumule and radicle
Parts of the peanut include:
- Shell – outer covering, in contact with soil
- Cotyledons – the main edible part
- Seed coat – brown paper-like covering of the edible part
- Radicle – embryonic root at the bottom of the cotyledon, which can be snapped off
- Plumule – embryonic shoot emerging from the top of the radicle
Phytochemistry
History
The Arachis genus is native to South America, east of the Andes, around Peru, Bolivia, Argentina, and Brazil. Cultivated peanuts arose from a hybrid between two wild species of peanut, thought to be A. duranensis and A. ipaensis. The initial hybrid would have been sterile, but spontaneous chromosome doubling restored its fertility, forming what is termed an amphidiploid or allotetraploid. Genetic analysis suggests the hybridization may have occurred only once and gave rise to A. monticola, a wild form of peanut that occurs in a few limited locations in northwestern Argentina, or in southeastern Bolivia, where the peanut landraces with the most wild-like features are grown today, and by artificial selection to A. hypogaea.The process of domestication through artificial selection made A. hypogaea dramatically different from its wild relatives. The domesticated plants are bushier, more compact, and have a different pod structure and larger seeds. From this center of origin, cultivation spread and formed secondary and tertiary centers of diversity in Peru, Ecuador, Brazil, Paraguay, and Uruguay. Over time, thousands of peanut landraces evolved; these are classified into six botanical varieties and two subspecies. Subspecies A. h. fastigiata types are more upright in their growth habit and have shorter crop cycles. Subspecies A. h. hypogaea types spread more on the ground and have longer crop cycles.
The oldest known archeological remains of pods have been dated at about 7,600 years old, possibly a wild species that was in cultivation, or A. hypogaea in the early phase of domestication. They were found in Peru, where dry climatic conditions are favorable for the preservation of organic material. Almost certainly, peanut cultivation predated this at the center of origin where the climate is moister. Many pre-Columbian cultures, such as the Moche, depicted peanuts in their art. Cultivation was well-established in Mesoamerica before the Spanish arrived. There, the conquistadors found the offered for sale in the marketplace of Tenochtitlan. Its cultivation was introduced in Europe in the 19th century through Spain, particularly Valencia, where it is still produced, albeit marginally. European traders later spread the peanut worldwide, and cultivation is now widespread in tropical and subtropical regions. In West Africa, it substantially replaced a crop plant from the same family, the Bambara groundnut, whose seed pods also develop underground. In China and India, it became an agricultural mainstay, and these countries are the largest producers in the world.
Peanuts were introduced to the US during the colonial period and grown as a garden crop. Starting in 1870, they were used as an animal feedstock until human consumption grew in the 1930s. George Washington Carver championed the peanut as part of his efforts for agricultural extension in the American South, where soils were depleted after repeated plantings of cotton. He invented and promulgated hundreds of peanut-based products, including cosmetics, paints, plastics, gasoline and nitroglycerin.
Peanut butter was first manufactured in Canada by a process patented in the US in 1884 by Marcellus Gilmore Edson of Montreal. Peanut butter became well known in the United States after the Beech-Nut company began selling it at the St. Louis World's Fair in 1904. The US Department of Agriculture initiated a program to encourage agricultural production and human consumption of peanuts in the late 19th and early 20th centuries.
Varieties
Cultivars in the United States
There are many peanut cultivars grown around the world. The market classes grown in the United States are Spanish, Runner, Virginia, and Valencia. Peanuts are produced in three major areas of the US: the southeastern US region which includes Alabama, Georgia, and Florida; the southwestern US region which includes New Mexico, Oklahoma, and Texas; and in the general eastern US which includes Virginia, North Carolina, and South Carolina. In Georgia, Naomi Chapman Woodroof is responsible for developing the breeding program of peanuts, resulting in a harvest almost five times greater.Certain cultivar groups are preferred for particular characteristics, such as differences in flavor, oil content, size, shape, and disease resistance. Most peanuts marketed in the shell are of the Virginia type, along with some Valencias selected for large size and the attractive appearance of the shell. Spanish peanuts are used mostly for peanut candy, salted nuts, and peanut butter.
Spanish group
The small Spanish types are grown in South Africa and the southwestern and southeastern United States. Until 1940, 90% of the peanuts grown in the US state of Georgia were Spanish types, but the trend since then has been larger-seeded, higher-yielding, more disease-resistant cultivars. Spanish peanuts have a higher oil content than other types of peanuts. In the US, the Spanish group is primarily grown in New Mexico, Oklahoma, and Texas.Cultivars of the Spanish group include 'Dixie Spanish', 'Improved Spanish 2B', 'GFA Spanish', 'Argentine', 'Spantex', 'Spanette', 'Shaffers Spanish', 'Natal Common ', "White Kernel Varieties', 'Starr', 'Comet', 'Florispan', 'Spanhoma', 'Spancross', 'OLin', 'Tamspan 90', 'AT 9899–14', 'Spanco', 'Wilco I', 'GG 2', 'GG 4', 'TMV 2', and 'Tamnut 06'.
Runner group
Since 1940, the southeastern US region has seen a shift to producing Runner group peanuts. This shift is due to good flavor, better roasting characteristics, and higher yields than Spanish types, leading to food manufacturers' preference for the use in peanut butter and salted nuts. Georgia's production is now almost 100% Runner-type.Cultivars of Runners include 'Southeastern Runner 56-15', 'Dixie Runner', 'Early Runner', 'Virginia Bunch 67', 'Bradford Runner', 'Egyptian Giant', 'Rhodesian Spanish Bunch', 'North Carolina Runner 56-15', 'Florunner', 'Virugard', 'Georgia Green', 'Tamrun 96', 'Flavor Runner 458', 'Tamrun OL01', 'Tamrun OL02' 'AT-120', 'Andru-93', 'Southern Runner', 'AT1-1', 'Georgia Brown', 'GK-7', and 'AT-108'.
Virginia group
The large-seeded Virginia group peanuts are grown in the US states of Virginia, North Carolina, Tennessee, Texas, New Mexico, Oklahoma, and parts of Georgia. They are increasing in popularity due to the demand for large peanuts for processing, particularly for salting, confections, and roasting in shells.Virginia group peanuts are either bunch or running in growth habit. The bunch type is upright to spreading. It attains a height of, and a spread of, with rows that seldom cover the ground. The pods are borne within of the base of the plant.
Cultivars of Virginia-type peanuts include 'NC 7', 'NC 9', 'NC 10C', 'NC-V 11', 'VA 93B', 'NC 12C', 'VA-C 92R', 'Gregory', 'VA 98R', 'Perry', 'Wilson, 'Hull', 'AT VC-2' and 'Shulamit'.