Wheat species, classes & varieties: how they differ and the impact on end-product
From the primitive type of wheat (Triticum Vulgaris), there have been different species, classes and varieties. Meeting customer and consumer needs starts with the wheat.
Particularity of wheat
Wheat is a unique grain in its ability to make the fully elastic dough required for leavened products. This is achieved from the gluten forming proteins it contains.
The grain is made of a succession of different layers (bran) protecting the endosperm and the germ. A particularity of the wheat is the presence of a crease that extends the full length of the grain and this complicates the process of separating the endosperm from the other layers during milling into flour.
Different species of wheat
Basically in Europe, soft wheat is used to produce flour and bread, whereas durum wheat is used to produce semolina and pasta.
Different varieties of wheat
Wheat varieties are often classed based on their:
- Endosperm texture (hard or soft)
- Sowing season (winter or spring), and
- Seed coat colour (e.g. red, white).
The functionality of the gluten is also frequently used to differentiate wheat varieties.
Protein content remains an important parameter for wheat trading, variety classification and in flour specifications. Broadly, the wheat flour contains two types of proteins:
- soluble proteins (including albumins and globulins), and
- insoluble proteins (including the gluten forming gliadins and glutenins).
The gluten quality is determined partly by the wheat variety. However, it is also affected by growing conditions (e.g. soil, weather conditions) and storage of the wheat and flour. Since the protein quantity and quality is distributed heterogeneously within the grain and endosperm, the milling process can also influence these two parameters in the flour.
The protein quality affects the rheology and mixing properties of the dough and, by extension, its processing behaviour. The glutenins are related to dough elasticity and the gliadins to dough extensibility. The gluten development characteristics, behaviour upon mixing and dough deformation under stress are very important for leavened products, such as bread.
Flour quality and functionality
Depending on the application, different flour characteristics are required - some of which will be very specific to the product. Flour functionality depends on a number of parameters and the main ones are determined by the proteins’ or starch characteristics.