The in vitro digestive mechanism of Tartary buckwheat starch-flavonoid complexes treated with different methods

The complexation of starch with flavonoids facilitates the formation of resistant starch. However, the dynamic structural evolution and molecular interactions with digestive enzymes remain to be systematically elucidated. This study employed in vitro simulated digestion coupled with multiscale structural analysis to investigate the effects of physical mixing (MIX), hydrothermal treatment (HT), and high hydrostatic pressure (HHP) treatment on the digestion behavior and mechanisms of Tartary buckwheat starch-flavonoid complexes. Results indicated that HHP treatment (200 and 400 MPa) significantly increased the complexation rate to over 90 %, which was more than 43 % higher than that of the MIX group. Moreover, HHP effectively delayed glucose release, with the 400 MPa group showing 17.9 % and 8.3 % lower cumulative glucose release compared to the MIX and HT group, respectively. Structural analyses revealed that HHP treatment strengthened hydrogen bonding and formed a unique crystalline structure, while scanning electron microscopy revealed intact granular morphology after digestion. Molecular dynamics simulations revealed that HHP complexes had a higher binding free energy with α-amylase and more stable intramolecular hydrogen-bond networks, thereby inhibiting enzymatic hydrolysis. Thus, HHP treatment modulates digestibility by optimizing the multi-level structure of complexes, providing a novel strategy for developing low glycemic-index foods.