Abstract: The research was designed to investigate the interactions of waxy corn starch (WCS) with ethanol extract of tea (EET) at different levels (1.0%, 2.5%, 5.0%, and 10.0%) during gelatinization and their effects on starch light transmittance, aging degree, solubility and swelling degree, gel strength, gelatinization and retrogradation properties, crystal structure, microstructure and in vitro digestibility. The results showed that the addition of EET had significant effects on the physicochemical properties, retrogradation properties and in vitro digestibility of WCS. With the addition of EET, the solubility and swelling degree of WCS increased gradually, while the gel strength decreased gradually. Compared with the control group, the aging degree, gelatinization enthalpy, retrogradation enthalpy, retrogradation rate, ratio of 1047/1022 and relative crystallinity of WCS with 2.5% EET added decreased, indicating significant inhibition of the retrogradation of WCS. The addition of EET to WCS decreased the digestibility of WCS, reduced the content of rapid digestible starch (RDS) and increased the content of resistant starch (RS). Therefore, adding a proper amount of EET to starchy foods can reduce the degree of starch retrogradation, improve the sensory quality and prolong the shelf life.

Key words: waxy corn starch; ethanol extract of tea; physicochemical properties; retrogradation properties; microstructure; in vitro digestibility