Insight into the structural and physicochemical properties of enzymatic debranched starch-EGCG complexes derived from three indica rice cultivars.

This study systematically investigated the multi-scale structures and physicochemical properties of debranched starch (DBS) and complexes formed by epigallocatechin gallate (EGCG) with gelatinized starch or debranched starch derived from three indica rice cultivars (Hly16, Ly6176, and Zz83). Among them, gelatinized starch-EGCG complexes (GS-EGCG) exhibited the weakest V-type diffraction peaks, whereas DBS displayed B- and V-type polymorphic crystalline structures and debranched starch-EGCG complexes (DBS-EGCG) formed stronger pure V-type crystals with higher relative crystallinity (15.73-20.04%). Starch debranching promoted the rearrangement of the short-range ordered structure and enhanced the binding capacity with EGCG, verifying its key role in forming stable V-type inclusion complexes with the increased enthalpy changes from 0.79-1.23 J/g to 2.62-4.28 J/g compared with GS-EGCG. Based on the results of the three tested cultivars, it was suggested that the short-range ordered structure and the single helix content were likely the major factors associated with the anti-digestive ability of DBS-EGCG. These findings provide a new insight for understanding the structural features of resistant starch and offer a theoretical guidance for selecting appropriate rice cultivars and processing methods to obtain the starch component with potential enhanced resistance.