International Starch: Wheat

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Wheat, common name for cereal grasses of a genus of the grass family, cultivated for food, such as bread, since prehistoric times by the peoples of the temperate zones and now the most important grain crop of those regions. Wheat is a tall, annual plant attaining an average height of 1.2 m (4 ft). The leaves, which resemble those of other grasses, appear early and are followed by slender stalks terminating in spikes, or so-called ears, of grain.

Production of wheat starch is described in TM33-2e

The main use of wheat is in the manufacture of flour for bread and cakes. In general, hard varieties are used for bread flour and pasta, and soft varieties for cake flour. Wheat is used also in the production of breakfast foods and to a limited extent in the making of beer, whisky, and industrial alcohol. Low grades of wheat, and by-products of the flour-milling, brewing, and distilling industries, are used as feed for livestock. A minor amount of wheat is used as a coffee substitute, and wheat starch is employed as a sizing for textile fabrics and for glucose syrups.

Wheat starch
(Amylum Tritici)
Two distinct types of granules are simple lenticular large granules 20 mm to 25 mm or up to 50 mm in diameter, and small spherical granules 5 mm to 10 mm in diameter. Striations are faintly marked and concentric.

In Europe and Australia in particular wheat is an important raw material for starch. In Europe the driving force is large surplus of wheat. Wheat gluten contribute equally to starch to the total revenue and from time to time starch may be the actual by-product to the manufacture of vital wheat gluten.

Species of wheat are classified according to the number of chromosomes found in the vegetative cell. They are divided into three series: the diploid, or einkorn, containing 14 chromosomes; the tetraploid, or emmer, containing 28 chromosomes; and the hexaploid, or bread wheat, containing 42 chromosomes. Wheat species cross-breed relatively frequently in nature. Selection of the best varieties for domestication took place over many centuries in many regions. Today, the varieties of common, club, and durum wheats are of the most importance commercially, but other species are still grown to suit local conditions, and they provide essential stock for systematic plant breeding programmes.

According to the regions in which they are grown, certain types of wheat are chosen for their adaptability to altitude, climate, and yield. The common wheats grown in northern Europe, Russia, the United States, and Canada are spring and winter wheats, planted either in the spring for summer harvest or in autumn for spring harvest. The colour of the grain varies from one type to another; white wheats are mostly winter wheats, red are spring wheats. Closely related to the common wheats are the club wheats, which have especially compact spikes, and spelta, in which the glumes (reduced, scale-like bracts) tightly enclose the grains. Durum wheat (Latin, durum, "hard") is so called because of the hardness of the grain. It is grown in the Mediterranean region for making pasta and has a very high gluten content. New high-yielding wheats were developed in the 1960s for use in developing countries, and research on them continued in the 1970s. Experimental programmes have produced commercial wheat varieties for hardiness and disease resistance. In 1978 the identification of a drought-resistant, high-protein, ancestral species growing in the Middle East held promise of still more highly improved wheat varieties.

Diseases of wheat are connected with parasitic fungi. The principal diseases are rust and smut. Wheat is also liable to injury from several insect pests; a particularly important insect pest is the Hessian fly.

In most countries wheat is usually planted by sowing machines of the drill or broadcast type. Little cultivation is necessary beyond preparation of the land by ploughing, harrowing, and, sometimes, dusting to control pests. Wheat crops are generally rotated with maize, hay, and pasture in regions with moderate rainfall and are rotated with oats and barley, or bare fallowing in drier regions.

Remains of both emmer and einkorn wheats have been found by archaeologists working on sites in the Middle East dating from the 7th millennium BC. Emmer was grown in predynastic Egypt; in prehistoric Europe it was grown in association with barley, einkorn, and club wheats. Bread wheat was identified at a 6th-millennium BC site in southern Turkistan, and a hexaploid (bread) wheat was found at Knossos in Crete. The cultivation of wheat in the Americas was introduced by the Spaniards in Mexico and by the English in New England and Virginia.

Scientific classification: Wheat makes up the genus Triticum of the family Gramineae. Einkorn wheat is classified as Triticum monococcum, emmer and durum wheats as Triticum turgidum, and bread wheat as Triticum aestivum.