Wheat

Scientific Name Triticum spp.
Common Names English: Wheat; German: Weizen; French: Blé; Spanish: Trigo

Occurrence

Agriculture Importance

Along with corn and rice, wheat is one of the most important food crops. It is grown on about 220 million hectares worldwide, covering more land area than any other crop. In 2014/2015, approximately 725 million metric tons were produced, most of it in China, India, Russia, USA and Canada (in that order).

Crop Management

for Wheat:

Cultivation

Wheat is more demanding with regard to soil, climatic conditions and water supply than other cereal crops. Ideally wheat requires heavy, deep and humous, but well-aerated soils with a high water capacity and a pH between 5.5 and 7.5. Nutrient-rich clay and black earth soils are ideal. Wheat is sensitive to soil salinity. Generally, varieties are divided into 'winter wheat' and 'summer wheat'. Winter wheat can withstand temperatures as low as -22°C (-7.6°F) and is sown in October; summer wheat, which yields much less but has a slightly higher protein content, in early spring. The most widely-cultivated of all Triticum varieties is 'soft wheat' (T.aestivum), which accounts for 90% of world production. The maturity of the grains is defined by their water content: 'milky-ripe' (50 %), 'waxy-ripe' or 'yellow-ripe' (30 %) and 'fully-ripe' (20 %).

At harvest, the wheat is 'dead-ripe' with a maximum water content of 16 %. Up until the middle of the 20th century, wheat was harvested with scythes, bound into sheaves for drying, and threshed later. Nowadays, large combine-harvesters (with cutter bars up to 10 m / 32.8 ft wide) are used, at least in the industrialised countries.

Cultivation Areas

Wheat is mainly grown in temperate zones, where it is too dry or cold for rice and corn, but also in the sub-tropics. Of all cereals, it is the most widely adapted; the highest yields, however, are achieved in the cooler parts of its ecological range. It has C3 carbon fixation and develops best at temperatures of 10-24°C (50 - 75.2°F). In warm climates it is therefore grown at high altitudes or during the cold season.

Special Information

The various wheat species (Triticum sp.) are probably the second oldest cultivated plants (after barley). They were first domesticated between 7500 and 6500 BC in the 'Fertile Crescent' region of the Middle East. The oldest evidence of systematic cultivation of wild wheat was found near the southern edge of the Euphrates valley during archaeological excavations at the Neolithic dwelling of Abu Hureyra. In historic times, wheat was already grown in ancient Greece, Persia, Egypt, and throughout Europe. In the oldest known historical records, it is also mentioned as an important crop. Spreading eastwards, it reached China around the third millennium BC; it arrived in the Americas with the Spanish fleet.

Initially, most cultivated wheat belonged to species such as einkorn (T.monococcum), emmer (T. diococcon) and, on a limited scale, rivet wheat (T.turgidum), but later, club wheat (T. compactum), durum wheat (T.durum) and spelt (T. spelta) were cultivated. Soft wheat (T. aestivum) did not gain its dominance until the Middle Ages. Wheat is a very variable crop - its taxonomy is complicated and partly obscure. Soft wheat (Triticum aestivum) is hexaploid and is thought to be a result of hybridisation, possibly between its (diploid or tetraploid) close relatives T.monococcum, Aegilops speltoides / T. speltoides and A. tauschii / T. tauschii. This is, however, controversial, as is the status of the genus Aegilops, which some authors do not regard as a self-contained taxon.

Taxonomy

Family

Triticum aestivum, the cultivated wheat, belongs to the family of sweet grasses (Poaceae, syn. Graminaeae).

Use

Food

Wheat is mainly used for human nutrition, but to a lesser extent as fodder for livestock. While starch accounts for nearly 60% of the grain's weight, the proteins (13-15%) are also of considerable nutritional importance.

Wheat is mainly used as a flour for making a huge variety of baked goods. There are various flour types, differing in their ratio of starch and protein content, which is determined by the extraction rate during the milling process. If all of the grain - including the outer bran and the germ - is ground, the result is vitamin- and protein-rich 'wholemeal flour', which is suitable for heavy doughs, e.g. leavened bread. A low extraction rate, achieved by grinding just the endosperm, produces a light and very white flour of somewhat lower nutritional value, which is most suitable for pastries and confectionery wares.

In some countries (e.g. Germany and France), the flour types are classified according to their ash content, which is a very accurate indicator for the extraction rate, as the endosperm contains much less (non-combustible) minerals than the outer layer of the grain. German flour types range from 405 (light) to 1600 (dark), the numbers representing the amount of ash (in mg) obtained by incinerating 100 g flour; in France they are just divided by ten.

The baking properties of a flour are essentially determined by its content of gluten, a water-binding, elastic substance that forms on contact with moisture from a mixture of proteins (namely Glutenin and Gliadin), lipids and carbohydrates. In wheat, gluten comprises about 80% of the protein contained. It gives the dough its elasticity and makes leavening possible by retaining the carbon dioxide bubbles produced by yeast or synthetic leaveners such as baking powder, thus causing the dough to rise. When the protein coagulates during baking, it stabilises the shape of the resulting product.

While flour is mostly made of soft wheat, durum wheat (T. durum) - accounting for only 5% of the wheat grown - is used for noodles (including all traditional Italian pastas), semolina, groats, couscous, bulgur and many other products.
During recent years, spelt has gained renewed popularity in organic farming due to its modest nutrient requirements, and it is valued for its distinct flavour.
Wheat is an ingredient of numerous processed foods. Wheat starch is a common food thickener in soups and sauces. Gluten is frequently used as an emulsifier, gelling- or stabilizing-agent in products such as ice-cream or ketchup.

Wheat can also be made into 'seitan', a replacement for meat in vegetarian, macrobiotic and Buddhist cuisine. Although invented in Japan (the word 'seitan' is a neologism of Japanese origin), it is most popular in China.

A considerable proportion of the wheat grains' most valuable ingredients are concentrated in the germs, which are a by-product of milling. They also contain 25% protein, a large amount of tocopherol, and vitamin B, and are therefore eaten as a food supplement. They can also be used to produce wheat-germ oil, which is valued for use in salads and other uncooked dishes.

Fodder

The wheat bran (husks remaining from the milling process) is used for feeding livestock and poultry. Straw, while also serving as a feedstuff, especially for ruminants, is mostly used for bedding.

Beverage

In a similar way to barley (Hordeum vulgare), wheat can also be malted for brewing beer (wheat beer or 'white beer'). A wide range of alcoholic beverages are made around the world by the distillation of a fermented mixture of wheat starch and malt (e.g. Korn Schnapps, some whiskies).

Industrial Products

Wheat starch can be used to make pastes, but it has largely been replaced for this purpose by methylcellulose. The straw is traditionally used for thatching and wickerwork; it can also be utilised to make pulp for paper etc. or as fuel.

Facts on selected crops