Altering structure and enzymatic resistance of high-amylose maize starch by irradiative depolymerization and annealing with palmitic acid as V-type inclusion compound

Abstract

This study explored a new physical modification approach to regulate enzymatic resistance of high-amylose starch for potentially better nutritional outcomes. High-amylose maize starch (HAMS) was subjected to chain depolymerization by electron beam irradiation (EBI), followed by inducing ordered structure through annealing in palmitic acid solution (APAS). APAS treatment significantly promotes the formation of ordered structure. Starch after the combinative modification showed up to 5.2 % increase in total crystallinity and up to 1.2 % increase in V-type fraction. The EBI-APAS modification led to increased gelatinization temperature (from 66.1 to 87.6 °C) and reduced final digested percentage under in vitro stimulated digestion conditions. The moderate extent of depolymerization resulted in higher enzymatic resistance, indicating that the extent of depolymerization is crucial in EBI-APAS modification. Pearson analysis showed a significant correlation between gelatinization onset temperature and digestion kinetic parameter (k1, rate constant of fast-phase digestion). Overall, the result suggests that ordered structures of degraded molecules induced by the combinative modification contribute to the enzymatic resistance of starch. This study sheds lights on future applications of EBI-APAS approach to regulate multi-scale structures and nutritional values of high-amylose starch.