Synergistic Effect of Extrusion and Polyphenol Treatment on Physicochemical Properties and Structural Characteristics of Corn Starch

In order to investigate the synergistic effect of extrusion and polyphenol treatment on the physicochemical and structural characteristics of corn starch (CS), four polyphenols (ferulic acid, gallic acid, quercetin and curcumin) were selected in this study. The solubility, swelling power, pasting properties, thermal characteristics, antioxidant capacity, in vitro digestibility and crystal structure of the extruded CS with polyphenols were evaluated. The results showed that extrusion combined with polyphenol treatment resulted in an increase in the solubility, swelling power and pasting temperature of CS, and a decrease in the gelatinization enthalpy, peak viscosity and setback value, as well as a significant improvement in the scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation and anti-digestive properties. The binding of polyphenols to CS was dominated by hydrogen bonding during the extrusion process, leading to a decrease in the short-range orderliness of CS and eventually the formation of a special V-shaped crystal structure. After the combined treatment, the structure of CS became denser as observed by scanning electron microscope (SEM). This study provides theoretical guidance for the application of polyphenols in extruded starch-based functional foods.