Oat
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? Oat |
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 Field of oats in Hemingway, South
Carolina
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| Avena
sativa Carolus Linnaeus (1753) |
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The Oat (Avena sativa) is a species of cereal grain, and the seeds of this plant. They are used for food for people and as fodder for animals, especially poultry and horses. Oat straw is used as animal bedding and sometimes as animal feed.
Oats are often served as a porridge made from rolled or crushed oats, oatmeal, and are also baked into cookies together with wheat flour. As oat flour or oatmeal, they are also used in a variety of other baked goods and cold cereals, and as an ingredient in muesli and granola. Oats may also be consumed raw, and cookies with raw oats are quickly becoming popular. Oats are also occasionally used in Britain for brewing beer. Oatmeal stout is one variety brewed using a percentage of oats for the wort.
Oat straw is also used in corn dolly making, and it is the favourite filling for home made lace pillows.
Oat extract can be used to soothe skin conditions, e.g. in baths, skin products, etc.
A now obsolete Middle English name for the plant was haver (which is still used in Dutch language however), surviving in the name of the livestock feeding bag haversack.
Distribution
Oats are native to Eurasia and appear to have been domesticated relatively late. They are now grown throughout the temperate zones. They have a lower summer heat requirement and greater tolerance of rain than other cereals like wheat, rye or barley, so are particularly important in areas with cool, wet summers such as northwest Europe, even being grown successfully in Iceland. Oats are an annual plant, and can be planted either in the fall (for late summer harvest) or in the spring (for early autumn harvest).
Historical attitudes towards oats vary. In England they were considered an inferior grain, while in Scotland they were, and still are, held in high esteem. A traditional saying in England is that "oats are only fit to be fed to horses and Scotsmen", to which the Scottish riposte is "and England has the finest horses, and Scotland the finest men". Samuel Johnson notoriously defined oats in his Dictionary as "a grain, which in England is generally given to horses, but in Scotland supports the people".
The discovery of the healthy cholesterol-lowering properties has led to wider appreciation of oats as human food. Oats grown in Scotland command a premium price throughout the United Kingdom as a result of these traditions.
Health
Oat bran is the outer casing of the oat. Its consumption is believed to lower LDL ("bad") cholesterol, and possibly to reduce the risk of heart disease. Oats are also a safe grain for people with celiac disease ( gluten intolerance). However, oats frequently get mixed up with small amounts of wheat during harvest and processing, so the EU officially lists them as a crop containing gluten. Oats from Ireland and Scotland, where less wheat is grown, are less likely to be contaminated in this way.
After reports found that oats can help lower cholesterol, an "oat bran craze" swept the U.S. in the late 1980s, peaking in 1989, when potato chips with added oat bran were marketed. The food fad was short-lived and faded by the early 1990s. The popularity of oatmeal and other oat products again increased after the January 1998 decision by the Food and Drug Administration (FDA) when it issued its final rule allowing a health claim to be made on the labels of foods containing "soluble fiber" from whole oats (oat bran, oat flour and rolled oats), noting that 3 grams of soluble fiber daily from these foods, in conjunction with a diet low in "saturated fat" and "cholesterol", and "low fat" may reduce the risk of heart disease. In order to qualify for the health claim, the whole oat-containing food must provide at least 0.75 grams of soluble fiber per serving. The soluble fiber in whole oats comprise a class of polysaccharides known as beta-D-glucans.
Beta-D-glucans, usually referred to as beta-glucans, comprise a class of non-digestible polysaccharides widely found in nature in such sources as oats, barley, yeast, bacteria, algae and mushrooms. In oats, barley and other cereal grains, they are located primarily in the endosperm cell wall.
Oat beta-glucan is a soluble fiber. It is a viscous polysaccharide made up of units of the sugar D-glucose. Oat beta-glucan is comprised of mixed-linkage polysaccharides. This means that the bonds between the D-glucose or D-glucopyranosyl units are either beta-1, 3 linkages or beta-1, 4 linkages. This type of beta-glucan is also referred to as a mixed-linkage (1→3), (1→4)-beta-D-glucan. The (1→3)-linkages break up the uniform structure of the beta-D-glucan molecule and make it soluble and flexible. In comparison, the nondigestible polysaccharide cellulose is also a beta-glucan but is non-soluble. The reason that it is non-soluble is that cellulose consists only of (1→4)-beta-D-linkages. The percentages of beta-glucan in the various whole oat products are: oat bran, greater than 5.5% and up to 23.0%; rolled oats, about 4%; whole oat flour about 4%.
Oats after corn(maize) has the highest lipid content of any cereal, e.g., >10 percent for oats and as high as 17 percent for some maize cultivars compared to about 2-3 percent for wheat and most other cereals. The polar lipid content of oats(about 8-17% glycolipid and 10-20% phospholipid or a total of about 33% ) is greater than that of other cereals since much of the lipid fraction is contained within the endosperm.
Protein
Oat is the only cereal containing a globulin or legume-like protein, avenalins, as the major (80%) storage protein. Globulins are characterized by water solubility and because of this property oats may be turned into milk but not into bread. The more typical cereal proteins, such as gluten are "prolamines." The minor protein of oat is a prolamine: avenin.
Oat protein is nearly equivalent in quality to soy protein which has been shown by the World Health Organization to be the equal of meat, milk and egg proteins. The protein content of the hull-less oat kernel -groat- ranges from 12-24%, the highest among cereals.
Agronomy
Oats are sown in the spring, as soon as the soil can be worked. An early start is crucial to good yields as oats will go dormant during the summer heat. Oats are cold-tolerant and will be unaffected by late frosts or snow. Typically about 100 kg/hectare (about 2 bushels per acre) are sown, either broadcast or drilled in 150 mm (6 inch) rows. Lower rates are used when underseeding with a legume. Somewhat higher rates can be used on the best soils. Excessive sowing rates will lead to problems with lodging and may reduce yields.
Winter oats may be grown as an off-season groundcover and plowed under in the spring as a green fertilizer.
Oats remove substantial amounts of nitrogen from the soil. If the straw is removed from the soil rather than being ploughed back, there will also be removal of large quantities of potash. Usually 50-100 kg/hectare (50-100 pounds per acre) of nitrogen in the form of urea or ammonium sulphate is sufficient. A sufficient amount of nitrogen is particularly important for plant height and hence straw quality and yield. When the prior-year crop was a legume, or where ample manure is applied, nitrogen rates can be reduced somewhat.
The vigorous growth habit of oats will tend to choke out most weeds. A few tall broadleaf weeds, such as ragweed, goosegrass and buttonweed (velvetleaf), can be a problem occasionally especially as they complicate harvest. These can be controlled with a modest application of a broadleaf herbicide such as 2,4-D while the weeds are still small.
Modern harvest technique is a matter of available equipment, local tradition, and priorities. Best yields are attained by swathing, cutting the plants at about 10 cm (4 inches) above ground and putting them into windrows with the grain all oriented the same way, just before the grain is completely ripe. The windrows are left to dry in the sun for several days before being combined using a dummy head. Then the straw is baled.
Oats can also be left standing until completely ripe and then combined with a grain head. This will lead to greater field losses as the grain falls from the heads and to harvesting losses as the grain is threshed out by the reel. Without a draper head, there will also be somewhat more damage to the straw since it will not be properly oriented as it enters the throat of the combine. Overall yield loss is 10-15% compared to proper swathing.
Late 19th and early 20th century harvesting was performed using a binder. Oats were gathered into shocks and then collected and run through a stationary threshing machine.
Earlier harvest involved cutting with a scythe or sickle, and threshing under the feet of cattle.
A good yield is typically about 3000 kg/hectare (100 bushels/acre) of grain and two tonnes of straw.