A- and B-type wheat starch granules: The multiscale structural evolution during digestion and the distinct digestion mechanisms.

The digestive characteristics of wheat starch are closely related to human health. However, the digestive mechanisms of distinct wheat starch granules are not well understood. To address this problem, A- and B-type wheat starch granules (AWS and BWS, respectively) were digested in vitro and the structural evolution of the digestive remnants was compared. After stomach-intestinal digestion of AWS, its crystallinity decreased from 12.75 % to 6.65 %, its fractal dimension decreased from 3.12 to 2.35, and the median particle size decreased from 20.613 to 10.135 μm. Additionally, the number of short chains (polymerization degree<14) and thermodynamic stability decreased after digestion. For BWS, Fourier transform infrared ratio of 1047/1022 cm and 995/1022 cm increased from 0.665 and 0.725 to 0.990 and 0.800, respectively. The median particle size decreased from 5.480 to 4.769 μm. An enzyme-resistant scattering peak was observed in the 1.35 nm lamellar structure. Additionally, the number of B and B chains and the thermodynamic stability increased after digestion. Our study confirmed that BWS is more likely than AWS to form enzyme-resistant structures during digestion. These findings provide insights into the distinct digestion mechanisms of AWS and BWS, and serve as a foundation for modifying wheat starch to increase its nutritional value.