Starch is an important renewable resource in nature. In this paper, the recent research advances in starch structure were systematically summarized from the granular and molecular levels. Meanwhile, the changes in starch multi-scale structures under different conditions were discussed. Furthermore, we redefine the growth ring structure of starch granule, and postulate a model for the fine structure of starch granule. It may provide important insights for the research of starch.

In this study, quercetin extracted from discarded Tartary buckwheat hulls was incorporated into buckwheat flour to enhance its RS content and nutritional value. The results showed: (1) at 5% addition, RS content reached 60.38%. (2) Quercetin penetrated starch granules and blocked pore structures, reducing the accessible surface area and hindering amylase hydrolysis: the first mechanism for RS increase. (3) The internal quercetin formed stable complexes with starch molecules (90 kJ/mol binding energy, 7 H-bonds), reconstructing the hydrogen bonding network, altering molecular arrangement, and modifying gelatinization properties. Due to steric hindrance, the starch molecule complexed with quercetin failed to fully insert into the α-amylase active groove, limiting contact with the catalytic triad: the second mechanism for RS increase. (4) External quercetin molecules bound stably within the α-amylase active groove (49 kJ/mol binding energy, 5 H-bonds), competitively inhibiting enzyme activity: the third mechanism for RS increase.