Classification of Wheat – Complete Guide
Wheat is the most widely cultivated plant in the world. The wheat that grows on Earth can even exceed the amount of all other seed-producing species, wild or domesticated. Each month of the year a mature wheat crop somewhere in the world. It is the most important crop in the United States and Canada and is growing in large areas in almost all countries in Latin America, Europe and Asia. Apparently, this cereal was one of the earliest cultivated plants. Recently the University archaeologist Robert Braidwood of Chicago has found charred wheat grains from 6700 years ago in the village of Jarmo, east of Iraq, the village is the oldest yet discovered and may have been one of where agriculture was born. When domesticated wheat, the man laid the foundations of Western civilization. No civilization has ever been founded with an agricultural base than that of cereals. The ancient cultures of Babylon and Egypt, Rome and Greece, and later the northern and western Europe, all were based on the cultivation of wheat, barley, rye and oats. The India, China and Japan had rice as the staple crop. The pre-Columbian peoples of America-Incas, Mayans and Aztecs grew corn for their daily bread.
What are the reasons for this close relationship between cereal and civilization? May be primarily a matter of nutrition. The cereal grain structure somewhat similar to a nut with a thin cover and the seed contains the embryo selo not a new plant but also a supply of food to feed. Cereal grains, like eggs and milk are foods that nature intended for the nutrition of young species. These are foods that contain the five nutrients: carbohydrates, proteins, fats, minerals and vitamins. A whole grain cereal, nutritional value if not destroyed because of modern methods of refining, it is better than any other plant product to provide an adequate ration. Perhaps the relationship between cereal and civilization is also a product of the discipline required of its grain growers. The only cereal grown from seed and should be planted and mowed in its proper season. This is different from root crops in mild climates can be planted and harvested at almost any time of year.
Both the Old and New World astronomy was invented by grain growers, and with it came a calendar and a system of arithmetic. Cereal farming to secure a stable food supply created the entertainment and leisure in turn protected the arts, crafts and sciences. It has been said that agriculture is the only cereal in the forms of food production that requires, rewards and encourages work and ingenuity in the same grade.
General Definition of Wheat
Plant annual grass, grass family, with spikes of the grains milled flour is removed. Its scientific name is the genus Triticum. One of the cereals used in food processing.
Source of wheat
It is thought that has been cultivated for over 9,000 years. Some believe that arose in the Nile River valley wheat enters Russian immigrants to America when he was brought to Kansas in 1873, called Turkey Red variety, which grows better than any other.
Distribution of wheat
Wheat is grown throughout the world, from the Arctic to near limits of Ecuador, although the harvest is most productive between 30 and 600 north latitude and between 27 and 400 south latitude. Altitudes range from sea level to 3,050 m in Kenya and 4572 m in Tibet. It is adaptable to different conditions, from the xerophytic, until the coast. The cultivars that are very different genealogy and grown under soil and climatic conditions varied, show very different characteristics.
The best crop of wheat field gets filled with loam and clay, although the performance is satisfactory in light terrain. The increase in harvest, offsets the strong nitrogen fertilization.
Weather conditions for growing wheat
Wheat thrives in subtropical climates, moderately warm and moderately cold. It is best annual rainfall of 229-762 mm, most abundant in spring than in summer. The average temperature in summer should be 13 ° C (56 ° F) or more.
Production of wheat
Topping the list by volume of world wheat production, are China, India, USA, Russia, France and Canada, in that order. Latin American countries appear even in the 14th with Argentina and Mexico at 25. The volume of China in 1992 was 3.733 million and Mexico in the same year was 115 million.
Supply of wheat
The sowing is done in late autumn (winter wheat) or spring (spring wheat). The times of sowing and harvesting of wheat in different Producers are naturally dependent upon special climatic conditions in some countries, wheat is harvested during all months of the year. Anyway possibilities silage most countries of wheat are enough to store most of the annual harvest, so that the British manufacturer of flour, you can buy wheat from any exporting country, almost any time year.
Classification of wheat - Sorted by vintage
Wheat has 2 growing seasons:
Winter Wheat: It is planted in autumn and harvested in spring. It can grow in places like northwestern Europe where it does not freeze over the floor. The seed germinates in autumn and grows slowly until spring. Frosts may adversely affect young plants, but a layer of snow protects them and leads to isolation.
Spring Wheat: It is planted in spring and harvested in early autumn. In places such as the Canadian prairies, or the Russian steppes who have winters too severe for sowing winter wheat is sown in spring, as soon as possible so that you can harvest the crop before the onset of autumn frosts. The climatic characteristics of the localities where wheat is grown high spring rainfall in spring and early summer and maximum temperature in the middle and end of summer favor the production of fast maturing grains with vitreous endosperm texture and high protein content suitable for making bread. The area of spring wheat production will gradually spread northward in the Northern Hemisphere, with the introduction of new varieties grown for their features of rapid maturation.
Winter wheat, grown in an atmosphere of constant temperature and more rainfall, crops ripen slowly producing higher performance and lower wealth protein more suitable for biscuits and pastry for baking.
Classification according to the endosperm texture
This feature of the grain is related to the shape of broken grain in the grinding, the glassy-mealy character can be changed with growing conditions. The development of mealy quality seem to be related to maturation.
The texture can be vitreous endosperm (steely, stony, glassy, cornea) The specific weight of vitreous grains is generally higher than the mealy grains: 1,422 the vitreous (Bailey, 1916). vitreous character is inherited, but is also affected by environmental conditions. The vitreous nature can be induced with nitrogen fertilizer or fertilizer and is positively correlated with high protein content, the floury character is positively correlated with obtaining high yields of grain. The grains are translucent and appear bright against the intense light. The vitreous endosperm lacks these fissures. Grains sometimes acquire a mealy appearance due to some treatments, for example by wetting and drying or repeatedly. heat treatment.
The wheat flour
Endosperm texture is floury (starchy, chalky). The specific weight of grain flour is 1.405 (Bailey, 1916). floury character is inherited and affected by environmental conditions. The mealy character is favored by heavy rain, light sandy soils and planting very dense and is more dependent on these conditions that the type of grain grown. The opacity of the mealy grains is an optical effect due to the presence of minute vacuoles or air-filled fissures between and perhaps within the endosperm cells. The cracks are internal reflective surfaces that prevent the transmission of light and give the endosperm appear white. Starchy grains are characteristic of varieties that grow slowly and have a long maturation period.
Classification according to the endosperm hardness
The 'toughness' and 'soft' are typical of milling, related to the way of fragmenting the endosperm. in durum wheat, the fracture tends to occur along the lines that limit the cells, while the endosperm of soft wheat is broken unexpectedly, at random. This phenomenon suggests areas of strengths and weaknesses mechanical durum wheat and fairly uniform weakness in wheat. One view is that the "hardness" is related to the degree of adhesion between starch and protein. Another way of putting it, that the hardness depends on the degree of continuity of protein matrix. The hardness affects the apparent ease with which the bran endosperm. In durum wheat, the endosperm cells are separated by more cleaning and tend to remain intact, while the wheat, the cells tend to fragment, shedding while another part remains attached to the bran.
Durum wheat flour produced thick, gritty, smooth and easy to sift, comprising regular shaped particles, many of which are full of endosperm cells.
Soft wheats produce very fine flour composed of irregular fragments of endosperm cells (including a proportion of very small cell fragments and loose grains of starch) and some crushed particles that stick together, hanging with difficulty and tends to seal off openings of the sieves. The injury that occurs in the starch grains on milling durum wheat, is higher than in wheat. According to Berg (1947), hardness is a characteristic that is transmitted in crosses and inherited according to Mendel's laws. The endosperm of durum wheat may look stony or floury, but always fragmentation is typical of durum wheat.
Classification by strength
Strong Wheat: Wheat that has the ability to produce flour for baking with pieces of great volume, good crumb texture and good storage properties, generally have high protein content. Wheat flour strong flour supports a proportion of loose, so the part will retain its large volume and good crumb structure while carrying a certain ratio of weak flour, it is also capable of absorbing and retaining a large amount of water.
Soft wheat: The wheat flour with which they can only get small loaves with thick, open crumb and characterized by its low protein content. Soft wheat flour is ideal for biscuits and cakes, but is unsuitable for baking unless it is mixed with flour stronger.
Its shape is oval with rounded ends, one of them excel in the germ and the other is a tuft of fine hairs known as the brush. Along the ventral surface is a depression (groove). In the bottom of the groove is an area heavily pigmented vascular
Plant of wheat
The height varies between 30 and 180 cm The stem is straight and cylindrical. Have some extent. The leaf is lancelet, with a width from .5 to 1 m and a length of 15 to 25 cm. Each plant is 4 to 6 leaves. The roots of wheat are similar to those of barley oats. Common wheat grains may be soft or hard.
Chemical Composition of wheat
The mature wheat grain is composed of: carbohydrates (crude fiber, starch, maltose, sucrose, glucose, melibiose, pentosans, galactose, raffinose), nitrogen compounds (mainly proteins: albumin, globulin, prolamin, residue) , lipids (ac. Acids: Myristic, palmitic, stearic, palmitooleico, oleic, linoleic, linoleic), minerals (K, P, S, Cl) and water along with small amounts of vitamins (inositol, choline and B complex) , enzymes (B-amylase, cellulase, glucosidase) and other substances such as pigments.
These nutrients are distributed in different areas of the wheat grain, and some are concentrated in specific regions. Starch is found only in the endosperm, crude fiber is reduced almost exclusively to the saved and the protein is found throughout the grain. About half of the total lipids are in the endosperm, the fifth in the seed and the rest in the bran, but the aleurone is richer than the pericarp and testa. More than half of the total minerals present in the pericarp, testa and aleurone.
Starch is the carbohydrate most important of all cereals, constituting about 64% of the dry matter of whole grain wheat and 70% of the endosperm. Form 70% of the wheat grain naturally. The carbohydrates present in cereal starch include (predominant), cellulose, hemi-cellulose, pentosans, dextrin, and sugars.
Starch consists of two main components: Amylose (25 -27%), an essentially linear polymer of alpha-(l - 4) glucose. Amylopectin, a branched structure strings randomly alpha-(l - 4) glucose branches linked by alpha-(1-6). Starch is insoluble in cold water. When heated with water, absorbs, swells and bursts, this is called gelation.
During mechanical milling can injure the grains of starch, starch plays an important role altered in the cooking process. Fiber is a carbohydrate polysaccharide that is not digested by lack of enzymes in the human body and is divided for analysis into two parts: Crude fiber that evaluates to the portion of the carbohydrates (more lignin) insoluble in dilute acids and alkalis under certain conditions.
Fiber is the indigestible part of the product remains undigested in the gut, including cellulose, non-cellulose polysaccharides (gums, mucilages, pectic substances, hemicelluloses) and lignin, an aromatic polymer hydrocarbonated not. The number of non-digestible fiber is always greater than the crude fiber, and that some components of non-digestible fiber is degraded during the valuation of raw fiber, but the relationship is constant.
In its primary structure, protein molecules are made up of chains of amino acids linked together by peptide bonds between the carboxyl group (COOH) of an amino acid and the amino group. In proteins of cereals are about 18 different amino acids. The proportions in which they are and their order in the chains, determine the properties of each protein. Foods made with wheat are sources of incomplete proteins. This means it may contain the 8 essential amino acids but not all of them at appropriate levels, so the combination of wheat with other foods provide to be correct, a complete protein. But compared with other cereals such as rice and corn come to the conclusion that it has more protein. The protein portion of wheat grain is located in the endosperm, embryo in greater abundance
Types of Proteins
Osborne classified wheat proteins into 4 categories based on their solubility characteristics. You can make a similar classification of the proteins of all cereals. The figure below shows the percentage of the 4 categories of proteins contained den durum wheat grain
Root: When a wheat seed germinates, it produces temporary roots. The permanent roots arise after the plant emerges into the soil, they are born with the knots that hold the plant in absorbing water and nutrients from the soil until it matures.
Stem: This is usually grown from 60 to 120cm. There are dwarf wheats that have a height of 25 to 30 cm tall wheats from 120 to 150 cm. There are also semi-dwarf wheats from 50 to 70 cm are most suitable for their performance.
Leaf: In each leaf node is born, this is composed of sheath and blade, between these two parties there is one that is called the lateral parts of which Cueli out some extensions called the atria. The blade has a length ranging from 15 to 25 cm and from .5 to 1 cm wide. The number of leaves varies from 4 to 6 cm and each leaf node is born.
Spike: It consists of spikelets arranged in a central axis called the rachis. The spikelets contain 2 to 5 flowers to form the grain. Not all flowers are fertile spikelet containing the number of spikelets varies from 8 to 12 depending on variety.
Fruit: The fruit is a grain of ovoid form with a groove on the ventral side. The grain is protected by the pericarp color-red or white depending on variety, the remainder being mostly consists of grain endosperm.
Cell Structure: Is the envelope of the fruit pericarp In mature wheat grain, the whole pericarp is thin and shriveled, the outer layers often fall off during cleaning, conditioning.
The pericarp enclosing the seed and is composed of several layers of cells. Basically this structure is divided into exocarp, mesocarp and endocarp. The primary functions of the pericarp are to protect the grain against external biotic (insects, microorganisms), to prevent moisture loss and lead and distribute water and other nutrients during germination. The pericarp is 5-7% of grain weight. Is characterized by containing high fiber and ash and totally lacking in starch. A. Exterior (Alas bee) The epidermis of caryopsides. It consists of rectangular cells, long thin-walled. The hypodermis is the next layer of the epidermis inwards and this is of variable thickness. Interior (endocarp) is divided into intermediate cells, and tubular cross. Intermediate cells of the outer pericarp, are oriented in the direction of the grain direction.
Cells cross: It consists of elongated cells in the transverse direction of the grain and are below the intermediate cells. Are long and cylindrical and position cuts across the grain. Its primary function is to prevent moisture driven by the tubular cells perish dei which can act as a seal or packing. Tubular cells: The innermost layer of the pericarp is torn considerably during ripening is a layer of branched cells as biphasic, called "tubular cells'.
They are about the same size as the Crusades, but its long axis runs parallel and along the grain. These cells have an important role by acting as a means of transmission and distribution of water to be absorbed through the seed during the germination process. Endosperm: The part of the starchy endosperm of wheat (usually called "endosperm") consists of thin-walled cells that vary in size, shape and composition in different parts of the endosperm. It consists mainly of starch and protein. Portion of the sub-aleurone: The cells adjacent to the aleurone (endosperm 'sub-aleurone) are small and cube form that are further away are elongated in the radial direction (prismatic endosperm cells), becoming larger and polygonal toward the center (cells central endosperm). In the cells of the sub-aleurone endosperm is relatively higher protein and starch grains are less crowded than the rest of the endosperm.
They contain starch granules, however have been high in protein (20%) concentrated in the aleurone grains, oil (20%) mainly contained in the esferosomas and minerals (20%) and phytic acid that is found in the aleurone granules and phytic bodies. The walls of these cells are thick with high fiber and have the ability to fluoresce when viewed under ultraviolet light. The aleurone layer plays an important role during germination because it synthesizes the enzymes needed to achieve unfolding of the compounds of the endosperm. In the specific case of wheat, the aleurone layer is considered part of the bran, and stir in the dry milling process to produce white flour or refined. called white wheats have been improved to lower the amount of pigment in the aleurone layer and especially for use in the production of breads with better color and flavor.
The peripheral endosperm is characterized by its high protein and starch units contain small, angular and compacted. This layer has been associated with a decline in the rate of digestibility of nutrients. Some processes such as rolling, heat treatment by steam explosion or bursting micronization and are intended primarily to destroy or modify this layer so that digestive enzymes have better access to the substrate.
The mature cells of the mature endosperm contain four basic structures: cell walls, starch granules and matrix protein bodies. Cell walls are thin and enclose the other components. They are high in insoluble fiber (cellulose and beta-glucans) and soluble (pentosans). Starch granules occupy most of the cellular space and are surrounded and separated by the protein matrix that serves to maintain the internal structure of the cell. The protein bodies are round and very small compared with the units of starch. They are scattered in the cellular space and mostly embedded in the membrane of the starch granules. In vitreous endosperm cells no air spaces and starch granules are well coated with the protein matrix, thus acquired angular shapes (polygonal>. This structure looks glassy or translucent because the light is diffracted when passing through the endosperm.
The starchy endosperm is enclosed by the vitreous is, is in the innermost part of the grain. It contains the same structures in the vitreous endosperm, but starch units are larger and less angular, the association between starch granules and protein matrix is weaker and starch units have less fouling of protein bodies, the walls phones are thinner and generally have a lower protein content than the previous one, in other words, these structures are not trapped as in the vitreous endosperm. This under the presence of tiny air spaces that give the endometrium starched or opaque appearance
The ratio between both endorse determines the hardness and density of the grain and therefore many factors affecting food processing. For example, during the shelling efficiency, the dry and wet milling and optimal cooking times are strongly influenced by grain hardness
Starch is found as lenticular or spherical granules between the protein bound tightly fills the intergranular spaces The size and shape of the starch grains of endosperm cells are simple. They have two sizes: large, 15-30 um in diameter, and small, 1-10 um, while the cells of the sub-aleurone endosperm are mainly of intermediate size, 15 um in diameter.
Testa (seed coat) and pigmented area
The cell walls of endosperm of wheat are composed mainly of pentosans (polymers of pentose sugars) by 75% in the form of arabinoxylan.
The testa is firmly attached to the ventral part of the tubular cells. It consists of one or two layers of cells. The color of some grains are partly dependent on the presence of pigments in these cell layers. For example, testa red winter wheat may be more heavily pigmented, substantially changing the color and / or appearance of the grain. When its head is present and contains the S gene of the dominant disperser contains condensed tannins, which produce brown or brown color in the grain. Tannins produce astringent or bitter tastes, so that seeds are more resistant to attack by birds. Another advantage is that the high tannin content is less susceptible to fungi and germination in the panicle. Unfortunately tannins nutritional quality because it lowers the digestibility of protein and have the ability to bind to digestive enzymes significantly decreasing hydrolytic capacity.
The germ is characterized by lack of starch and its high oil content, protein, soluble sugars and ash. It is also high in vitamins B and E and generates most of the enzymes for the germination process. Cereals, pearl millet, maize and sorghum contain the greatest proportion of germ
Basically, the seed contains the embryo axis and escutelum or shield.
This structure is bonded or fused to the endosperm through the shield. This tissue and epithelium are morphologically the only cotyledon of grasses. It serves as a storehouse of nutrients and as a communication bridge between the seedling or embryo development and the department store of nutrients of the endosperm. the scutellum is the seat of the majority of vitamin B.
The embryonic axis is axis or differentiation of the embryo. It consists of the radical and plumule (covered by the coleoptiles) that will form roots (primary root covered by coleorhizae and secondary lateral roots) and the vegetative part of the plant.
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