CULINARY INFO
Corn

Corn : Maize
Native to Mexico, corn has been cultivated for thousands of years; both as a vegetable and a source of meal. The dried grains, when ground are known as cornmeal or cornflour. Bourbon whisky, originating in America, is a fermented corn and the grain is also used in the manufacture of corn syrup and corn oil.

Corn, Zea mays, is one of the world's most important human and stock food crops. Two colour types of sweet corn are yellow, the most common (center), and white (right).

The slender oat stalk grows up to 1.2 m (4 ft) high, it is an annual plant of the grass family, Gramineae. The largest of the cereals, it can reach heights of 4.5 m (15 ft). The stem, or cornstalk, is hard and jointed, resembling bamboo. The plant possesses both male and female flowers; the male flowers are borne in the tassel at the top of the stalk, and the female is a cluster, called a cob, at a joint of the stalk.<

The corn silks hanging from the husk of each cob are the pollen receptors; each thread of silk must receive a grain of pollen in order for its fruit, or kernel, to develop. A fertilised cob, or ear, contains eight or more rows of kernels. One to three or more cobs grow on each stalk.

Among the world's four most important crops (the others are wheat, rice, and potatoes), corn is one of the few economic plants native to America. The United States produces over 40 percent of the world output. Worldwide, more than 132 million ha (327 million acres) of land are planted in corn each year, with a grain production of more than 477 million metric tons (more than 526 million U.S. tons). Countries with large areas devoted to corn include the United States, China, Brazil, Russia, Mexico, Argentina, Romania, France, India, and South Africa.

Origin of corn
Archaeological and geological excavations, and measures of radioactive decay of old ears of corn found in caves, indicate that a type of primitive corn was used as a food in Mexico at least 7,000 years ago. No wild forms of corn have been found, and the origin of domesticated corn is a speculative and controversial issue.

In its present form, the corn plant is highly specialised, and is unsuited for efficient, natural reproduction. Although the ear is specially constructed for producing high seed yields, the plant has no mechanism for broadcasting its seeds without human intervention. The processes of mutation, natural selection, and mass selection by the American Indians gradually transformed certain varieties of wild corn into the cultivated plant called maize--a cultigen, or a product of human culture.

Corn was unknown outside the New World before 1492, but the plant was extensively cultivated, in all its present forms, by the Indians of North and South America. Seed grains of Indian maize, brought to Europe and Africa by 16th-century explorers, were planted and eventually thrived throughout most of the world. Since the 1930s, the development of hybrid varieties of corn has resulted in greatly increased yields and improved quality. Today, corn is considerably larger in cob size and in the number and weight of the kernels than the corn grown by the Indians.

Cultivation
Corn grows best in well-aerated, deep, warm loams containing an abundance of organic matter, nitrogen, phosphorus, and potassium. The crop thrives in areas with moderately high summer temperatures, warm nights, and adequate but not excessive rainfall that is well distributed during the growing season. Length of the growing season and length of day also influence production. The Corn Belt of the mid-western United States is ideally suited to these conditions.

In areas of intensive corn cultivation--especially in the Corn Belt where farms are large and the topography is relatively flat--mechanisation has resulted in higher corn yields and greater crop-labour productivity. Many specialised machines are used throughout the Corn Belt. Among the most important are wheel-track planters, which dig the furrows, plant the seed, and cover it in one operation; mechanical corn pickers, which harvest only the ears (some machines shell the ears as well); and field choppers, which cut and chop the stalks into silage.

Pest control is accomplished through the use of pest-resistant hybrid varieties, proper cultivation, and the judicious use of herbicides and pesticides (see HERBICIDE; PESTICIDES AND PEST CONTROL). Viral and other diseases have caused heavy crop losses during the past 2 decades, and plant geneticists are doing research in types of corn that are resistant to specific diseases and insects.

Yields from desirable corn hybrids are greatest when plants are grown in soils well supplied with balanced amounts of plant food and considerable soil moisture, especially in areas of low rainfall. Corn grown continuously for 100 years on the experimental Morrow Plots at the University of Illinois now ranges in yield from about 3,136 kg/ha (50 bu/acre) to 10,035 kg/ha (160 bu/acre), the disparity depending entirely on the treatment of the soil.

Use of adapted hybrids, increased nitrogen application, and heavy plant populations contributed to an annual increase of 157 kg/ha (2.5 bu/acre) of corn during each of the past 25 years in the Corn Belt of the United States. Other contributing factors were favourable soil and climatic conditions, efficient mechanisation, effective pest control, modern cultural practices, intelligent water management, and greater crop-labour productivity.

Before 1930, more than 30 minutes of labour were required to produce a bushel (25.4 kg) of corn in the United States; less than 3 minutes is now required.

Types and characteristics

Dent Corn
By far the most widely grown type, dent corn (so named because the seed has a depression, or dent, in the crown) furnishes millions of tons of grain for human and industrial use and for livestock feed. The soft starch extends to the summit of the seed, and the sides have a corneous starch. The characteristic denting is caused by rapid drying and shrinkage of the soft starch.

Flint Corn
The kernels of flint corn are hard and smooth and contain little soft starch. Columbus and those who followed him landed in countries where flint strains were widely grown. Consequently, flint corn was probably the type first seen by Europeans. Flint corn is more widely grown in Europe, Asia, Central America, and South America than in the United States. In temperate zones, flint corn often matures earlier, germinates better, and has earlier plant vigour than dent strains.

Popcorn
Popcorn, an extreme form of flint, contains only a small proportion of soft starch. A minor crop, it is grown primarily for human consumption as freshly popped corn and popcorn confections. The ability to pop seems to be conditioned by the quality of the horny endosperm, a tough, elastic material that resists the steam pressure generated within the heated kernel until it reaches explosive force.

Flour Corn
The kernels of flour corn are composed largely of soft starch and have little or no dent. Although it is now of little importance, flour corn has been widely grown in the drier sections of the United States and in the Andean region of South America. An old type of corn, it is frequently found in graves of the ancient Aztecs and Incas. Because of the softness of the kernels, American Indians were able to grind them for flour.

Sweet Corn
The kernels of sweet corn have a translucent, horny appearance when immature and are wrinkled when dry. The ears are eaten fresh or are canned. Sweet corn differs from dent corn by only one recessive gene, which prevents some sugar from being converted into starch. A considerable quantity is grown as a winter crop in the southern part of the United States.

Waxy Corn
The kernels of this corn are waxy in appearance. Its starch differs chemically from common corn starch. Corn having the recessive waxy gene was developed in China. Waxy mutations have since occurred in American dent strains. Waxy hybrids are grown on a small scale to produce a starch similar to tapioca starch.

Podcorn
Although not grown commercially, podcorn is of interest in studying the origin of corn, since it is thought to resemble varieties of primitive corn. Each kernel is enclosed in a pod or husk and the entire ear is also enclosed in a husk (as are the ears of other types of corn).

Development of hybrids
More is known about the genetics of corn than about any other economic plant or animal. The plant is well suited for genetic research, since it is easily grown and is adaptable to a wide range of environmental conditions. It has a large number of distinct hereditary variations. Inbreeding, or crossing, is simple and rapid, and hundreds of kernels may be obtained on one ear from a single pollination. Rates of mutation for specific genes can be measured, and the comparatively small number of relatively large chromosomes within the germ cell facilitates cytological studies.

Beginning in the 1920s, a method for breeding hybrid corn was developed, using crossbreeding between inbred lines. Normally, corn is cross-pollinated: pollen is carried from one plant to another by wind or insects. Inbred corn is self-fertilised; that is, pollen from the tassel is used to fertilise the plant's silks, which are protected from chance pollination by other plants. Inbreeding is often continued through several generations, using only those progeny that show desirable characteristics. Producing cross-strains, or hybrids, by cross-breeding different varieties of inbred corn involves complex techniques. Since the 1930s, the results from breeding and cultivating hybrid corn have been spectacular.

Corn and such other monocot grains as rice and wheat proved less amenable to the standard GENETIC ENGINEERING techniques than such broad-leaved dicots as tobacco and tomatoes. Scientists successfully introduced a foreign gene into corn for the first time in 1988, and researchers believe that this genetic manipulation will lead to the development of improved varieties of corn and other cereals.

Perennial Hybrid Corn
A perennial variety of teosinte, a wild grass closely related to corn, has been discovered in the mountains of the state of Jalisco in Mexico. The variety, Zea diploperennis, carries only 20 chromosomes, as does corn; it is hoped that when the plants are crossbred, the new hybrid will grow perennially and also have the ability to tolerate moist and even wet soils.

Production Increases from Corn Hybrids
Acreage of corn hybrids in the United States has increased from less than 0.1 percent in 1931 to practically 100 percent today. Grain yields increased from 1,538 kg/ha (24.5 bu/acre) in 1931 to 7,408 kg/ha (118.6 bu/acre) in 1985.

Commercial uses
Increased yields from the use of hybrids, as well as modern production practices, have made vast quantities of corn available for feeding livestock and for human consumption, as well as furnishing the raw materials for hundreds of industrial products. Corn is used primarily as a food in many areas of the world, although in the United States well over half of the crop is fed to livestock.