The impact of the soluble protein fraction and kernel hardness on wheat flour starch digestibility

Wheat is the staple crop for 35% of the world's population, providing a major source of calories, mainly in the form of starch. The digestibility of wheat starch varies between different flours and products. Wheat products that are rapidly digested elicit large post-prandial glucose peaks associated with metabolic disorders. We investigated the impact of protein on starch digestion in three commercial flours with different grain hardness. A soluble extract of wheat proteins reduced starch digestion, even following gastric proteolysis. This extract was enriched in proteinaceous alpha-amylase inhibitors which were partially degraded during gastric proteolysis. Starch digestion kinetic analysis was carried out for flour samples pre-treated with different pepsin activities. The rate of starch digestion was altered following pepsin pre-digestion, and the extent of starch digestion increased in response to pepsin pre-digestion. We conclude that soluble proteinaceous alpha-amylase inhibitors present in wheat can escape gastric digestion and significantly contribute to reducing starch digestion in the small intestine.

Automated summary

Wheat is a major staple crop for a significant portion of the world's population, providing calories in the form of starch. Protein in wheat, particularly the proteinaceous alpha-amylase inhibitors, can reduce starch digestion, even after gastric proteolysis. The rate and extent of starch digestion can be altered by pepsin pre-digestion. Soluble proteinaceous alpha-amylase inhibitors present in wheat can escape gastric digestion and significantly contribute to reducing starch digestion in the small intestine.