What is wheat quality and why is it important?
Wheat quality means different things to different people. 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 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 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
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.
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)