Flour’s water absorption rate is meant by the maximal water addition volume when four is made into dough, indicated by percentage (%). Water absorption rate has a direct influence on the production rate of foodstuff. For flour products such as steamed buns and bread, the more the water absorbed is, the larger number of the steamed buns and bread from the same flour weight is. Many factors influence the dough’s water absorption rate: mainly flour granule disposition, protein content, non-starch polysaccharides, starch damage, water content, etc. Of which there are three most important factors: protein content, starch damage and non-starch polysaccharides.
The protein in flour is categorized as water soluble protein and water insoluble protein (gluten protein). Researches show that water soluble protein and water insoluble protein both absorb water, but the water absorption of water insoluble protein (gluten protein) is more important and has a great bearing on dough’s water absorption rate. When water insoluble protein absorbs water, it can form a viscoelastic network structure unique to dough. Starch damage means the damage of starch’s outer cell membrane caused by mechanical grinding and pressing during milling process. Damaged starch is decomposed into dextrin, maltose and glucose under the effect of acid and enzyme, which play an important role in water absorption during dough’s fermentation and baking periods. The water absorption rate of damaged starch can reach 200%, which is five times that of complete starch granules.
Obvious negative correlation exists between gluten content and dough’s water absorption rate; no correlation exists between water holdup rate and dough’s water absorption rate; while obvious positive correlation exists between damaged starch content and dough’s water absorption rate.
As damaged starch influences dough’s water absorption rate to great extent, damaged starch content is high and dough’s water absorption rate is high, and thus the production rate of flour products is high. Therefore, damaged starch content should be increased properly in order to improve the production rate of flour products. However, researches show that high starch damage rate will affect product quality, so damaged starch contents should be properly adjusted according to different usages of tailored flours.