Enzymatic resistance of starch-polyphenol inclusion complexes: polyphenol inhibition and structural changes during in vitro digestion

High amylose corn starch (HACS) forms inclusion complexes with polyphenols, resulting in a significant reduction in starch digestibility. The digestibility of the inclusion complexes is influenced by the inhibitory effects of polyphenols on amylases and/or the structural characteristics of the inclusion complex. Herein, nine distinct polyphenols complexed with HACS through high-temperature water method. Four representative inclusion complexes—HACS-caffeic acid inclusion complex (HACS-CA), HACS-dihydroxybenzoic acid inclusion complex (HACS-DA), HACS-soy isoflavone inclusion complex (HACS-SI), and HACS-naringenin inclusion complex (HACS-NG)—were selected for comparative analysis of the in vitro digestion processes. The results revealed that the HACS-polyphenol inclusion complexes inhibited α-amylase activity by gradually releasing polyphenols during digestion. The release rates of polyphenols followed the sequence of HACS-DA < HACS-SI < HACS-CA ≈ HACS-NG, and the inhibition of α-amylase occurred in the opposite sequence. Structural analyses showed an increase in the proportion of super-long amylopectin chains and the degree of order of digested HACS-DA and HACS-SI. The enzymatic resistance of the complexes was related to the super-long amylopectin chains recombined to form a short-range ordered structure. This study broadens the understanding of the enzymatic resistance of starch-polyphenol complexes, offering valuable insights into their potential applications in developing functional foods with health benefits.