What is wheat quality and why is it important?

While farmers generally look at yield and productions costs, millers need to predict the resulting flour type and baking quality. The quality of a wheat class is determined by its suitability for a specific final product.

What makes a good wheat today?

Quality Attributes

Quality of wheat and flour is primarily determined by wheat type, hardness, protein content, sedimentation value, falling number, alveolarity, water absorption and baking volume. Millers need to regard many other parameters too. In practice, however, the commercial value of wheat is determined by protein content alone.

Protein content

Protein content is a key specification for wheat since it is related to many processing properties, such as water absorption and gluten strength. protein content also can be related to finished-product attributes, such as texture and appearance. Acceptable levels depend on targeted use, expecially flour type. In general, high quality flours require a protein content of at least 12%

Proteins drive quality

Glutens

The gluten forming proteins of wheat, known as gliadins and glutenins, are what make bread possible. When flour and water are mixed, the gluten forming proteins begin to organize and cross-link so that a gluten web is formed. It is this protein web that allows the baker to shape the dough and have it remain in that shape instead of simply flowing across the table. This web also traps the carbon dioxide gas produced by the yeast during fermentation, allowing the loaf to rise. The concentration of gluten forming proteins is an important number that millers need to evaluate in each lot of grain.

Nitrogen

There can be differences in the quality of the protein, such that two flours with similar protein measures can give different baking results. In general, however, the protein concentration gives a good overall indication of the probable success of the flour in bread baking. The assumption is made that as the total amount of protein increases so does the amount of the gluten forming proteins. Rather than measuring actual protein concentration, laboratories determine nitrogen concentration. They then apply a conversion factor to estimate protein content. For wheat the conversion factor is 5.7 (i.e. "crude protein" = nitrogen 5.7).

Proteins are made of nitrogen

Proteins build up in the grain at the end of the vegetation cycle. The protein content in the wheat grain is dependent on genotype but is also clearly influenced by environmental variables such as water access and temperature during growth especially through the grain filling period. The most effective environmental factor on wheat quality, however, is nitrogen supply. Proper management of nitrogen fertilizer ensures high quality wheat.

• Roughly 80 % of the nitrogen (and thus protein content) of the grains originates from stems and leaves and was absorbed earlier in the vegetation period. It is transferred to the grains during the senescence. 
• The remaining 20% of nitrogen is accumulated after flowering by additional supply of nitrogen from the soil.

Markets Request Protein

Wheat markets are highly segmented: interior markets and export markets have their own requirements, but all are based on key characteristics such as protein content.

• The biggest market for wheat is animal nutrition. While price and specific weight traditionally used to be the main drivers, producers of animal feedstuff are increasingly attentive to protein content for its nutritional qualities. 
• Starch production requires a steady supply of homogeneous batches. Overall quality criteria are similar to flour milling. 
• Human nutrition is characterised by a very strong segmentation of end products and processes with specific requirements for each of them. There is a general trend towards bread types requiring flour with high protein content. Frosted goods also need higher protein content.
• For export trading, protein content is the primary criteria for wheat quality. In recent years, European production (especially from France) fell short of the requirements in many foreign markets and was replaced by wheat of other origins.