Rheological, thermal and in vitro digestibility properties on complex of plasma modified Tartary buckwheat starches with quercetin

Starch-polyphenols complex with unique physicochemical and functional properties has gained research interests. As a method of physical modification, plasma treatment leads to smaller fragments of starch, which increases the possibility of binding with polyphenols. In this study, pregelatinized plasma-modified Tartary buckwheat starch (pre-TBS-P), as a new material, was combined with quercetin forming complexes (pre-TBS-P-Q). The rheological and thermal properties, and digestibility of pre-TBS-P-Q were investigated. Results show that quercetin complexation increased the consistency coefficient and decreased the flow behavior index. A more compact and stable structure after combining quercetin was observed using SEM and TGA. The results of XRD and FT-IR identified that quercetin was bound to starch through hydrogen bonds, forming the non-inclusive complex with higher crystallinity. Compared with pregelatinized Tartary buckwheat starch (pre-TBS), the digestion rate of both pre-TBS-P and pre-TBS-P-Q decreased. The velocity constant in the first-order digestion ranked as pre-TBS < pre-TBS-P < pre-TBS-P-Q. Conclusively, using the combination of plasma treatment and complexation with quercetin, the digestion velocity of pre-TBS-P-Q complex decreased due to the increased viscosity of starch solution, as well as, the enhanced crystallinity and compactness of starch granules.