Starch facilitates enzymatic wheat gluten hydrolysis

Summary

Wheat gluten can be hydrolyzed by either using (vital) wheat gluten or directly from wheat flour. This study investigates the influence of the presence of starch, the main component of wheat, on enzymatic wheat gluten hydrolysis. Wheat gluten present in wheat flour (WFG) and vital wheat gluten (VWG) were hydrolyzed at constant protein concentrations, but subsequently 5.6 times higher amounts of wheat flour. Nevertheless, WFG hydrolysis at 40% total solids resulted in significantly higher degrees of hydrolysis (DH%) than VWG hydrolysis at 7.2% solids. This difference increased to up to 4.5% in 6 h and diminished again for longer reaction times. Possible differences in the gluten composition and the presence of albumins and globulins in wheat flour could not explain the difference in DH% because the addition of starch to VWG increased the rate of hydrolysis similarly. Instead, it was concluded that starch granules impede gluten aggregation, which facilitates the hydrolysis. At higher solid concentrations of up to 70% wheat flour, the positive effect of starch disappeared, because WFG hydrolysis was hindered by mass transfer limitations and lower water activities.