Wheat
Economic importance
Wheat is the most important food crop: more than half of the world's population consumes it as food. Wheat flour is used in baking and the confectionery industry. Bread has high taste and nutritional qualities. Wheat grain is used to produce groats, pasta, wheat starch, dextrin, alcohol, and other products.
By-products of flour milling—wheat bran and flour dust—are used as concentrated feed for animals. Straw and chaff are also used for feed, but recently they have increasingly been used as organic fertilizer.
The most important indicators of wheat quality are protein and gluten content. Protein content is affected by climate, soil conditions, and applied fertilizers. Protein content determines its use; it can vary from 9 to 26%, protein digestibility reaches 95%, and lipid and ash contents are about 2% each. For baking, grain with a protein content of 14-15% is used; for pasta, 17-18%.
Wheat protein is represented by albumins (water-soluble), globulins (soluble in salt solutions), prolamins (soluble in alcohols), and glutelins (soluble in weak alkalis and acids). In a hydrated state, prolamins and glutelins form a jelly, a clot that remains after washing starch from dough. This jelly is called gluten. In wheat protein, its content is up to 50% wet gluten.
For evaluating the baking properties of wheat flour, gluten quantity and quality are important; they affect loaf volume, spread, and crumb porosity. According to physical properties, gluten is divided into:
- with good elasticity and medium extensibility;
- with satisfactory elasticity or strong extensibility;
- with unsatisfactory elasticity or weak extensibility.
High loaf volume depends on gluten elasticity and the gas-retention capacity of dough. Gluten extensibility should be not more than 30 cm and not less than 20 cm. Bread spread is the ratio of bread height to its diameter. The spread of good-quality bread should be more than 0.5. The crumb should have a uniform, thin-walled, fine-grained, porous structure.
For baking, grain with a protein content of not less than 11% is used; for pasta, not less than 14%.
History of the crop
Wheat is one of the oldest crops cultivated on Earth. Archaeological research shows that it was cultivated more than 6,500 years ago in the territory of modern Iraq, in 6000 BC in Egypt, and in 3000 BC in China. Even in prehistoric times, wheat spread in Africa and Europe.
In the territory of Russia, wheat was known in the Stone Age—around the 3rd-4th millennium BC. It was cultivated in Turkmenistan, Transcaucasia, and Ukraine. In 3000 BC it was known in Georgia and Armenia; traces of this crop were found in Khmelnytskyi Oblast of Ukraine, dated to the 4th millennium BC. The Scythians were engaged in cultivating this crop, and later the Slavs, who spread it north to Novgorod and Ladoga. In the 13th century it was grown in Khakassia and other regions of Siberia, for example, in the territory of Krasnoyarsk Krai. Transcaucasia has the greatest diversity of wheat species.
World production
In world agriculture, wheat ranks first among crops. Sown areas are 230-240 million ha, which is 32% of the total area of cereal crops. Gross harvest is 600 million t, or 29% of total grain production. Average yield is 2.6 t/ha. In terms of sown area and wheat grain production, the USSR ranked first in the world. In 1976-1980, the average wheat sown area in the USSR was 60.7 million ha. In the 1990s, the sown area in Russia was 25 million ha, which was 11% of the world total. In 2001-2005, wheat sown area was 24 million ha, gross harvest was 44 million t, or 57% of the total grain harvest, and average yield was 1.83 t/ha.
Large sown areas are in the USA, China, India, Canada, Argentina, France, and Australia. Wheat is cultivated on all continents, in mountains up to 4000 m above sea level. In European countries and the USA, winter wheat is more common; in Russia and Canada, due to the harsh climate, spring wheat is more common.
Species
The genus Wheat (Triticum spp.) includes 22 species, which belong to the grass family Poaceae (formerly cereals or grasses, Gramineae). The largest sown areas in the world are occupied by soft (Triticum aestivum L., syn. Triticum vulgare L.) and durum (Triticum durum Desf.) wheat.
The division of species into varieties is based only on morphologically stable characters of the ear and grain. This classification does not give an idea of the biological nature of the forms and does not link them with ecology and geography. The classification is of practical importance, as it serves for the morphological taxonomy of cultivars.
Characters of wheat varieties:
- awnedness, that is, presence or absence of awns on the ear;
- pubescence of glumes, which may also be bare;
- ear color, e.g., white, red, black;
- awn color: same as ear color or black in white and red ears;
- grain color, more often white and red;
- white-colored grain includes pure white, yellowish, and pale pink; red-colored grain includes dark pink, red, and reddish brown.
Each variety has a series of cultivars differing from one another, though not always, in morphological characters, biological and production characteristics. Within one variety there may be winter and spring cultivars, early-ripening and late-ripening; they may differ in winter hardiness, drought resistance, shattering, and resistance to diseases and pests.
Most wheat species, including soft and durum, turgidum, polonicum, dwarf, persicum, and round-grained, are naked-grained, characterized by a non-brittle rachis. For this reason, after ripening their ear does not break up into spikelets, and during threshing the grain separates well from the glumes and lemmas.
Spelt, or hulled wheat species, are distinguished by a brittle rachis; therefore, after ripening the ear breaks into spikelets, and during threshing the grain does not separate from the spikelets. To obtain clean grain of hulled species, special dehulling is used. Hulled species include wild and cultivated einkorn, emmer, spelt, and macha. In some regions of the North Caucasus, local spelt cultivars are cultivated.
Strong and durum wheats are of great importance for the milling and baking industry and for export.
Soft wheat
Soft, or common, wheat is more widespread and is cultivated throughout Russia. There are winter, semi-winter, and spring forms of soft wheat. The ear is loose. The 1000-seed weight varies from 30 to 55 g. The front side of the ear exceeds the lateral side, i.e., the width is greater than the thickness. Glumes are broad, not completely covering the lemmas. The keel on the glume is narrow and weakly developed; the grain has a well-defined brush; in consistency it may be mealy, semi-vitreous, or vitreous. There are awned and awnless forms. The awns on the outer lemmas are shorter; the ears diverge in a fan-like manner. The straw is hollow.
Durum wheat
Durum wheat in Russia is mainly represented by spring forms. Winter forms are cultivated on small areas in the lowland-foothill regions of Azerbaijan, in eastern Georgia, in Odesa Oblast of Ukraine, and in Russia—in Dagestan, Siberia, the Volga region, Kuban, and the Central Black Earth zone. In the world, the main regions of durum wheat cultivation are the Mediterranean coast: Spain, France, Italy, Asia Minor, north and south Africa, the USA, Argentina, and Australia.
Durum wheat ears are long; the glumes strongly cover the flower; the keel is prominent; the grain is completely immersed in the lemmas. For this reason, durum wheat better resists shattering, but its threshing is also more difficult. The ear is dense and awned. The awns are parallel to the ear and longer than it; the lateral side of the ear exceeds the front, i.e., the thickness is greater than the width. The grain is elongated, laterally compressed, with a weakly expressed brush or almost without one, and vitreous in break. The cross-section of the grain is angular; in soft wheat it is close to round. The 1000-seed weight is from 35 to 65 g. The straw of durum wheat in the upper internode is filled or has a small cavity.
Differences between soft and durum wheat
Most cultivars of soft wheat belong to the varieties lutescens, erythrospermum, ferrugineum, and milturum. Durum wheat cultivars belong to hordeiforme and melanopus.
The gluten of soft wheat has more valuable properties, due to which bread from soft wheat flour has higher quality. The gluten of durum wheat is tearing, so it is used for the production of semolina and pasta. Durum wheat grain is valued higher than soft wheat grain.
Table. Morphological differences between soft and durum wheat.
| Soft wheat | Durum wheat | |
|---|---|---|
| Ear | Awned or awnless, loose. Front side wider than lateral | Awned, rarely awnless. Large, dense, cross-section square or compressed, with lateral side wider than front |
| Awns | Equal to the ear or shorter, diverging to the sides | Longer than the ear, directed upward parallel to the ear |
| Straw under the ear | More often hollow | More often filled with pith |
| Grain | Short with a brush. Round in break, mealy or semi-vitreous. Protein content 10-18% | Elongated. Brush weakly expressed or absent. Angular and vitreous in break. Protein content 16-24% |
Strong, medium, and weak wheats
Strong wheats are only soft; they are characterized by increased content of protein, gluten, and other nutrients. When assessing wheat strength, baking properties are decisive. According to the technological properties of grain, three types of wheat are distinguished: strong, medium, and weak.
Strong wheat (strong) is characterized by a higher protein content in the grain—not less than 14%, wet gluten—not less than 28%, gluten quality not lower than group I, loaf volume from 100 g of flour—550 cm3, grain vitreousness in red-grained wheat—not less than 75%, in white-grained—not less than 60%, baking strength of flour—not less than 280 J.
Strong wheat is called an improver because it improves the baking qualities of weak wheat. When flour from strong wheat grain is added to weak wheat flour, the bread quality improves: taste, porosity, and volume. Strong wheat grain is valued on the international market.
Medium-strength wheat (filler) has good baking qualities; bread from it is of satisfactory quality without adding stronger wheat, but it cannot improve weak wheat. Medium wheat grain contains 11-13.9% protein, 25-27% gluten, gluten quality corresponds to group II, and baking strength of flour is 200-280 J.
Weak (weak) wheat has low baking strength. Bread is of reduced volume and spreads out. Weak wheat grain is characterized by low protein content—less than 11%, wet gluten—less than 25%, gluten quality corresponds to group II-III, loaf volume from 100 g of flour less than 400 cm3, and baking strength of flour—less than 200 J. To obtain standard bread from weak wheat flour, strong wheat flour is added to it.
Wheats valuable for grain quality are those that have genetically increased flour strength, but insufficient to be effective improvers of weak wheat in grain quality. Valuable wheat grain should contain not less than 25% gluten of quality not lower than group II.
Strong wheat grain is valued higher than ordinary grain.
The most widespread strong-quality cultivars are:
- winter wheat — Mironovskaya 808, Bezostaya 1, Odesskaya 51, Donskaya ostistaya;
- spring wheat — Albidum 43, Saratovskaya 29, Saratovskaya 39, Bezenchukskaya 98.
The most valuable quality cultivars of winter wheat include Albidum 114 and Ilyichevka; of spring wheat—Grekum 114, Minskaya, and Moskovskaya 35.
Spring wheat
Main page: Spring wheat
Winter wheat
Main page: Winter wheat
References
- Kolomeychenko V. V. (2007). Crop Production/Textbook. Moscow: Agrobusinesscenter.
- Vavilov P. P., Gritsenko V. V., Kuznetsov V. S. et al. (1986). Crop Production. Ed. Vavilov P. P. 5th ed., revised and enlarged. Moscow: Agropromizdat.
- Niklyaev V. S. (2000). Fundamentals of agricultural production technology. Farming and crop production. Moscow: Bylina.
