Study on the formation mechanism of Tartary buckwheat starch-flavonoid complexes with different treatments

Abstract

The complexation of Tartary buckwheat starch with flavonoids facilitates the preparation of resistant starch. However, the research on the formation mechanism of Tartary buckwheat starch-flavonoid complexes under various treatment methods remains limited. In this study, we investigated the effects of high hydrostatic pressure treatment and heat treatment on Tartary buckwheat starch-flavonoid complexes (BSF), and explored the binding mechanisms between Tartary buckwheat starch (TBS) and flavonoids. The results demonstrated that the degree and type of BSF were significantly altered under different treatments. UV and fluorescence spectra analysis revealed that the binding mechanism of starch and flavonoids differed under high hydrostatic pressure (HHP) treatment compared to heat treatment. Interaction force studies indicated that in the HT complex, starch and flavonoids were primarily bonded via hydrogen bonds, whereas in the HHP treated complex, bonding occurred through both hydrogen bonds and hydrophobic interactions. The conformational changes, solubility, interaction energy, solvation free energy, and binding free energy of the complexes were systematically investigated using molecular dynamics simulations. High hydrostatic pressure facilitates complex formation through hydrogen bonding and hydrophobic interactions, with 400 MPa HHP exhibiting the highest binding energy (−49.93 kcal/mol). Heat treatment promotes complex formation predominantly through hydrogen bonding but with lower binding energy (−37.47 kcal/mol). Overall, HHP enables flavonoids to enter the starch spiral cavity, resulting in a more compact structure, while heat treatment induces starch despiralization of starch, thereby increasing the binding sites available for flavonoids.