Wheat grain is composed of the following substances: 7 to 18% protein (depending on the type of wheat), 60 to 70% starch, 2 to 2.5% cellulose (crude fiber), 1.5 to 2% fat and the rest composed of Moisture and minerals, the physical appearance of wheat grains is very diverse. Wheat grains vary in length from 5 to 8 mm, in width from 2.5 to 4.5 mm and in weight from 20 to 60 mg. Wheat ranges in color from beige or pea (known as white wheat) to reddish brown (known as red wheat). Depending on the different components of the endosperm, the grains can have a soft or firm texture. Wheat grain structure is composed of the following components:
Seedlings:
(Other names of seedlings are: buds, embryos and embryos) It makes up about 2.5% of the seed weight and is rich in fats and vitamins, especially B vitamins. The unique feature of sprouts is their high fat content. But due to the low share of sprouts in the whole grain, the percentage of total fat in the grain is low and between 1 and 1.5 percent. Since this part is usually separated in the preparation of wheat flour with bran, bran can not be stored for a long time.
Bran:
It is the same as the grain husk and makes up about 14% of the grain weight. Bran, like seedlings, is separated from the grain during the flouring stage and is usually used for animal feed. Bran is rich in cellulose.
Bran is practically made up of 7 separate layers, the most important of which is the testa layer. Testa is the presence of pigments, especially carotenoids, so this layer is extremely important.
Endosperm: Contains wheat starch and makes up approximately 83 to 87% of the total grain. The endosperm contains starch grains and proteins whose starch grains are bound together by gluten, one of the proteins in the grains, to form the protein-starch matrix. The amount of gluten in the grain varies depending on the type and breed of wheat. A layer of endosperm is located just below the bran called the alveoli. This is a single-celled layer that separates in the flour-making process. Endosperm contains between 10 and 15% protein and a significant portion of it is starch.
It is the amount of gluten in wheat that determines its quality. Hard spring and autumn red wheat have more gluten and therefore are more valuable than bread. Because dough made from flour, which is rich in gluten, due to its elasticity, is able to retain more fermentation gases, and therefore, the dough comes out better and its volume increases. The quality of bread baking mainly depends on two factors: the quality and quantity of gluten in the dough.
The amount of gluten is effective in ripening and increasing the volume of bread. Wheats that have more gluten are also better baked. The quality of gluten can not replace the quantity, because good quality wheat gluten may produce flour that is unstable and loose in the bakery. The amount of wheat gluten depends a lot on the weather conditions, but with the help of wheat seed modification, its quantity can be increased. Atmospheric conditions more than different wheat cultivars in changing the amount of effective white matter and the maximum amount of gluten can be obtained in warm areas. Climate is 70% and cultivar type is 30% effective in grain gluten content. In bakery, the quality of gluten is just as important as its quantity. The quality of gluten depends on its resistance to the pressure of the gases created by the fermentation, as well as its stability against the expansion and loosening of the dough (without tearing). In other words, the dough should be stable for a while during kneading and not loosen soon. In this way, the wall of air bubbles inside the dough does not rupture quickly, and as a result, the bread becomes larger. When the dough rises, a lot of fermentation must be done to increase the amount of gases and increase the volume of bread.
Plant gluten quality is largely determined by its genetic background: Gluten quality can not be altered by changes in environmental conditions or by the use of fertilizers. Higher levels of protein, which mainly increase the quality of the bakery, indicate that the quality of gluten is good. Higher levels in low-quality protein cultivars only lead to very limited improvements in bakery quality.
In order to increase the quality of flour bakery, on the one hand, the percentage of growth and development that improves the quality of gluten should be increased, such as the quality of wheat (Manitoba) and on the other hand, the quantity of gluten should be increased by breeding methods (for example, in West Germany Gluten has increased from 19% to 25-23%) and finally the percentage of oats or bran should be
Decreased (6%). Also, by adding table salt (in small amounts) to the dough, the stability and strength of gluten increases and the dough tolerance increases when kneading and mixing. (High concentration of salt weakens the stability and strength of the dough.)
Gluten is composed of two components, glutenin (weakly soluble in base) and gliadin (relatively strong in alcohol). Glutenin causes the dough to stick and gliadin causes the dough to stretch. Glutamine is used to separate gluten from starch. Gliadin is done by gluten centrifugation at high speeds. A good dough is a dough that has proportionate amounts of both components. According to Irani (2006), the percentage of wet gluten should not be less than 27 and the gluten index (gluten quality number) should be in the range of 90-50. It seems that under stress conditions, due to the sharp increase in the accumulation of gliadin proteins (gliadin proteins are heat shock-like proteins and increase plant resistance to inanimate stresses) and
Decreased (6%). Also, by adding table salt (in small amounts) to the dough, the stability and strength of gluten increases and the dough tolerance increases when kneading and mixing. (High concentration of salt weakens the stability and strength of the dough.)
Gluten is composed of two components, glutenin (weakly soluble in base) and gliadin (relatively strong in alcohol). Glutenin causes the dough to stick and gliadin causes the dough to stretch. Glutamine is used to separate gluten from starch. Gliadin is done by gluten centrifugation at high speeds. A good dough is a dough that has proportionate amounts of both components. According to Irani (2006), the percentage of wet gluten should not be less than 27 and the gluten index (gluten quality number) should be in the range of 90-50. It seems that under stress conditions, due to the sharp increase in the accumulation of gliadin proteins (gliadin proteins are heat shock-like proteins and increase plant resistance to abiotic stresses) and a small decrease in gluten protein levels, gluten index (ratio of gluten to total gluten) ) Is reduced and as a result the strength and quality of the dough is reduced.
Types of wheat:
Botanically, wheat is a member of the species Triticum, which is divided into three distinct groups, and each group has a specific number of chromosomes that have all the genetic characteristics of the family.
Wheat genetics are more difficult than most other crops because some wheat varieties are diploid and have two chromosome strands, while many other wheat varieties are polyploid and have four chromosome strands (tetraploid) or six (hexaploid). [
Diploids, which are found only in forest and desert areas, and monocotyledonous wheat are also in this group.
• Tetraploids, which are wild and emer and wheat durum wheat are in this group.
• Hexaploids, which include bread wheat.
In terms of type of cultivation, wheat is usually divided into two general categories of spring wheat and autumn wheat. These two types, in addition to their seeds being different in color, texture, shape and., Also have different growth and development conditions. These two types of wheat are cultivated at two different times of the year. Wheat grain has a groove that is located along the grain. The depth of this groove is high in autumn wheat and low in spring wheat. The sides of this groove are round in spring wheat and angular in autumn wheat].
Spring wheat: Sown in early spring. After germination, the young plant grows in spring and early summer and the crop is harvested until late summer. Spring wheat is usually grown in areas where autumn wheat can not withstand the harsh winter cold of those areas. Of course, the yield of autumn wheat is higher than spring. Spring wheat is usually sown after seed preparation and when the soil temperature reaches one degree Celsius above zero. If weather conditions allow, wheat can be planted earlier to extend its growth period and increase its yield. Autumn wheat must be exposed to cold weather for a long time in order to reach the flowering stage. If autumn wheat is planted in spring, because it does not pass the cold period, it can not form a good inflorescence.
Autumn wheat: This type of wheat is grown in the northern hemisphere in the fall when the soil temperature is below 13 degrees Celsius. First, the seeds of autumn wheat germinate. Then in winter, the plant remains as a small young plant and with the beginning of spring, it begins to grow again. Usually in one of the months of June, July or finally August, the seeds ripen and are ready to be harvested. Autumn wheat has deeper and thicker roots than spring wheat, which penetrate up to 200 cm into the soil. This is due to the fact that autumn wheat has a longer growing season.
Suitable conditions for wheat growth:
Deep sandy and loamy soil with good drainage is suitable for wheat growth. Basically, the yield of wheat in rainfed conditions (irrigation with rain) is higher in fine-textured soils. Because such soils are able to retain water better and longer. But in irrigated conditions (where the farmer irrigates the plant himself), usually not much wheat is affected by the texture of its soil. Wheat, like other plants, can not germinate in dry soil.
Spring wheat always has its required moisture due to the storage of winter moisture in the soil. But the soil moisture of autumn wheat usually hinders the germination process. If the soil does not have enough moisture for germination or early growth, the seeds may rot or be exposed to cold damage.
Suitable climate for wheat growth
Ideal conditions for wheat growth are cool climate during vegetative growth period, temperate climate during grain formation period and hot and dry climate at harvest time; Therefore, in areas with severe winters, wheat cultivation faces problems such as winter frosts. Of course, we must know that wheat is not very resistant to drought and can not tolerate drought and dehydration for a long time. However, it is able to adapt to dry conditions to some extent, and by forming smaller cells that eventually cause smaller leaves to form, resulting in smaller pores, it can reduce sweating levels and be somewhat protected from the adverse effects of dehydration.
Wheat plant pests and diseases:
Wheat age
Wheat age (Eurygaster integriceps) is one of the most dangerous pests of wheat after locusts and causes a lot of annual damage to wheat fields.
Age damage occurs in two different stages