The influence mechanism of pH and hydrothermal processing on the interaction between cyanidin-3-O-glucoside and starch

The influence of the system pH (3, 5, and 7) and hydrothermal processing of starch (65 °C/10 min and 95 °C/20 min) on the interaction between cyanidin-3-O-glucoside (C3G) and starch (corn starch, potato starch, and pea starch) were investigated from the molecular interaction force level, molecular structure level, and microscopic level to the macroscopic level. The binding rates and binding amounts are found to increase with increasing pH of the system, and the use of a moderate extent of hydrothermal processing of starch (65 °C/10 min) can elevate the binding rates and binding amounts at pH 5 and 7, that is 65 °C/10 min treated would have a best binding effect compared with 95 °C/20 min treated and untreated starch at pH 5 and 7.With increasing pH, more hydrogen bonds are formed between C3G and starch molecular chains due to the structural changes of C3G at high pH. As the degree of hydrothermal processing of the starch is enhanced, the starch structure is gradually broken, and more starch molecular chains are released, for which the chance to contact C3G improves, enhancing the binding rates and binding amounts, that is the binding rates and binding amounts of 65 °C/10 min and 95 °C/20 min treated are higher than untreated starch. In particular, compared with 95 °C/20 min treated starch, 65 °C/10 min treated starch maintains the spatial three-dimensional structure better and forms more binding cavities and sites. Furthermore, increasing the system pH and the use of a moderate extent of hydrothermal processing simultaneously show a synergistic effect. • The highest binding rate is achieved at pH 7 and 65 °C/10 min of processing. • With increasing pH, electrostatic interactions change to hydrogen bond formation. • The 65 °C/10 min treated starch has a spatial effect. • PH and hydrothermal processing show a synergistic effect.