An agricultural crop grown for its grain and straw in most countries of the temperate zones of the world. In the major oat-growing states of the midwestern United States (Iowa, North Dakota, South Dakota, Minnesota, and Wisconsin) the crop is raised for grain, whereas in the Southern states (Texas, Oklahoma, and Georgia) it is used for pasture or a combination of pasture and grain. About 90% of the annual oat grain production is used for animal feeds, and about 10% is processed into food for humans, for example, oatmeal and other cereal products. In general, oats are a cool-season crop which requires a moist climate. They grow well on both light and heavy soils if sufficient moisture and fertility nutrients are available. See also Cereal.
The fifteen species of oats in the genus Avena are divided into three groups on the basis of chromosome number: 14, 28, or 42. Within the 42-chromosome cultivated species there is wide variation among varieties for all plant traits. Oats belong to the Graminae (grass) family; thus the oat plant forms a crown at the soil surface from which a fibrous root system penetrates the soil. Culms usually grow 2–5 ft (0.6–1.5 m) tall, and they are terminated with inflorescences called panicles. Each panicle usually bears 10–75 spikelets on its numerous branches. A spikelet is enclosed by two papery glumes and bears two or three florets, each with an ovary, two stigmas, and three anthers enclosed in a lemma and palea (see illustration). In most varieties the lemma and palea adhere to the oat seed after threshing. A trait used to determine market grade of oats is the color of the lemma, which may be white, yellow, gray, brown, red, or black. The major trait that distinguishes wild from cultivated oats is seed shattering. In cultivated species the seed attachment is persistent, and it can be separated from the panicle only by threshing. See also Cyperales; Flower; Grass crops;

An oat flower; two oat grains are shown at the lower right.
The world collection of oats, maintained by the U.S. Department of Agriculture, contains more than 14,000 lines of 42-chromosome types. These represent lines from wild species and from varieties produced at breeding stations. The collection represents a vast range of genetic types that can be used for varietal improvement.
The milling of oats is less complex than wheat milling and has many similarities to rice or barley milling operations because there is limited fractionation of the kernel. The oat grain is covered with a coarse, adhering hull which must be removed prior to production of ingredients or consumer foods. Oats as received at the mill house are termed green oats and must be cleaned to remove foreign seeds and trash. Clean, sound oats are heated slowly prior to hull removal. The green oats have active lipolytic enzymes (lipases) which will catalyze hydrolysis of triglycerides and yield free fatty acids. The heating, drying, or roasting procedures inactivate lipases, facilitate hull removal, and impart a distinctive roasted flavor to the oat product. Roasted oats are air-cooled and size-graded prior to dehulling. The products of the dehuller are primarily the whole kernel or groat and the fiber hull which are readily separated by air aspiration. The low-density oat hulls possess particularly high levels of fiber and pentosans which are suitable feedstock for industrial production of furfural (an important chemical nylon manufacturing) through high-temperature acid hydrolysis and dehydration. Whole, cleaned oat groats are not frequently available in the commercial food market. Selected large-sized groats are excellent for puffing into ready-to-eat cereals.
Oat cutting and flaking procedures provide more extensive utilization of groats in the form of rolled oats. Oat flour is obtained from further reduction and sieving or hammer milling of the whole groat or flaked product. This high-protein flour is frequently used in the formulations of ready-to-eat cereals and many prepared baby foods. Composite flours blended from oat flour and other cereals providing high protein content and extended shelf life have been proposed as suitable for world feeding programs. See also Food manufacturing.






