Multiscale Structural Changes of Wheat and Yam Starches during Cooking and Their Effect on in Vitro Enzymatic Digestibility.

In the present study, the multiscale structures and in vitro digestibility of wheat and yam starches with different water contents after heating at 100 °C were investigated. After heating for the same time, the degree of gelatinization of both starches increased with increasing water content, followed by the gradual disruption of multiscale structures of starch granules. At a water content of 37% for wheat and 46% for yam starch, both starches were almost completely gelatinized after heating for 5 min at 100 °C. Heat treatment increased greatly in vitro enzymatic digestibility of both starches, especially at a water content of >28%. It is interesting to note that extending heat treatment did not further disrupt the multiscale structures nor increase the in vitro enzymatic digestibility of both starches with the same water content. In contrast to wheat starch, yam starch showed a higher resistance to heat treatment. From this study, we can conclude that water content plays a more important role in determining the gelatinization behavior and in vitro enzymatic digestibility of starch than the duration of heating.