Unraveling the key structural characteristics enhancing digestion resistance of wheat starch-mung bean hull polyphenols complexes

Mung bean hull polyphenols (MBPs) have the potential to retard starch digestion by altering its multi-scale structures. However, the regulatory mechanism and the key structural characteristics that contribute to digestion resistance remain unclear. In this study, MBPs were non-covalently interacted with wheat starch (WS) under hydrothermal treatments. The digestibility of WS was negatively correlated with the addition of MBPs. The multi-scale structures investigated by ¹³C CP/MAS NMR, FT-IR, XRD, SAXS, and SEM unveiled the formation of single helix, short-range ordered, and V-type crystalline structures. Notably, MBPs could also induce the entanglements of glucan chains to form compact aggregates that were non- or weakly-crystalline. Correlation and stepwise regression analyses demonstrated that ordered structures were prerequisites for digestion resistance of WS-MBPs complexes, with tightly packed amorphous aggregates playing a secondary yet significant role. This study provides new insights into the relation between starch multi-scale structures and digestion resistance.