Two genetically different types of wheat crop have developed over the years and dominate the area of production:
Wheat can be classified into a number of groups according to varietal characteristics as follows:
Winter wheat is typically sown in September and harvested the following August (Northern Hemisphere). It is unique in its vernalisation requirement. This is the need to experience a period of cold which enables the plant to flower. Vernalisation refers to a requirement in wheat to undergo a period of low temperatures in order to trigger flowering. It is an inherited characteristic that prevents winter wheat developing a flowering meristem too early and consequently being damaged by cold weather.
The plants response to vernalisation is dependent on two factors, the temperature during ,and the duration of the vernalisation period. Vernalisation is complete once the meristem of the plant has reached the double-ridge stage. There are three principle temperatures involved in the process:
Research suggests that there is a clear linear response to vernalisation between 0 and 8°C. True winter wheat's are said to require exposure to the optimum vernalisation temperatures for 50 days. This is known as the effective days to saturate the response to vernalisation.
In contrast, spring wheat does not require cold temperatures (vernalisation) to trigger flowering and thus is sown from January / February onwards, with harvest being in August. The growing season varies between 120 days to 180 days depending on the climate. Spring types usually require temperatures between 7° and 18°C for 5 to 15 days for floral induction.
Wheat types can be classified in terms of their endosperm texture which can be hard or soft:
Hard wheat has a high protein content and is suitable for bread flours. The starch grains are hard and do not break up in the milling process.
Soft wheat has a soft endosperm where the starch grains break up during milling. Used for french bread, biscuits and 'flour‘.
Wheat with hard dark-coloured kernels high in gluten and used for bread and pasta; grown especially in southern Russia, North Africa, and northern central North America.
Wheat types can be classified in terms of their grain quality:
These are varieties that produce consistent milling and baking performance. Millers will offer a premium above base prices for these providing they achieve the specified quality requirements including 13% protein, 250s Hagberg Falling Number (HFN) and a specific weight of 76kg/hl.;
This group comprises varieties that exhibit bread-making potential, but are not suited to all grists. Some are consistent, but not as good as those in Group 1; some perform inconsistently whilst others are suited to specialist flours.
This Group contains soft varieties for biscuit, cake and other flours where the main requirement is for soft milling characteristics, low protein, good extraction rates, and an extensible but not elastic gluten.
These varieties are grown mainly as livestock feed wheat's.
Each of the wheat classes are used to produce flour for various baking industries.
All-purpose flour is the most common of all the flours, this comes from the finely ground part of the wheat kernel called the endosperm. It is made from a combination of hard and soft wheat, and used for a variety of baked products – yeast breads, cakes, biscuits and pastries.
Bread flour is milled for commercial baking use. While being similar to all-purpose flour, it has a higher gluten content.
Self-rising flour is a type of all-purpose flour that has salt and a leavening agent added. It is commonly used in biscuits.
Cake flour is fine-textured being milled from soft wheat and has a low protein content. It is used to make all types of baked goods such as cakes, cookies, crackers, and some types of pastry. Cake flour has a higher percentage of starch and less protein than bread flour.
Semolina is the coarsely ground endosperm of durum wheat. Durum wheat is the hardest variety of wheat and has the highest protein content. This makes it ideal for making high-quality pasta and couscous.
Durum flour is a by-product in the production of semolina. It is usually enriched with four B vitamins and iron, and used to make noodles.