Effect of endogenous proteins and heat treatment on the in vitro digestibility and physicochemical properties of corn flour

Starch and protein in corn flour (CF) exist in the form of coexistence, which provides an opportunity to reduce the digestibility of CF by using protein. This study aimed to investigate the effects of endogenous proteins and heat treatment during processing on CF digestibility, with emphasis on establishing relevant physicochemical mechanisms. The in vitro digestibility of CF was significantly decreased compared with that of CF without protein (CF-P); the rapidly digestible starch (RDS) content decreased from 91.37% to 77.52%, and the resistant starch (RS) content increased from 4.58% to 15.18%. Similarly, the three heat treatments could reduce starch digestibility of CF. The microstructure showed that proteins can partially or completely encapsulate starch granules to form aggregates of starch granules bound by proteins. The presence of protein and heat treatment can significantly reduce the swelling power of CF and increase the gelatinization temperature of CF, which has a certain correlation with the RS content. The existence of strong hydrogen bonds and disulfide bond (S-S) between starch and protein can improve the thermal stability and interaction force of starch and effectively protect starch granules from shearing. Protein competed with starch for water molecules that may delay the rate of water entering starch and increase the gelatinization temperature. These findings have significant implications for CF food design. • Endogenous protein and heat treatment reduced the digestibility of corn flour. • The interaction between protein and starch were hydrogen bond and disulfide bond. • Protein was more hydrophilic to compete water molecules with starch. • Heat treatment reduced swelling power and increased gelatinization temperature.