Microstructure, gelatinization and pasting properties of rice starch under acid and heat treatments

Microstructure of starch plays a vital role in the physicochemical properties. In this study, the microstructure, gelatinization and pasting properties of rice starches after acid, heat and acid-heat treatments were investigated. In our findings, molecular weight and size, amylopectin chain length distribution, degree of branching, amylose content, relative crystallinity, and hot water-solubility of rice starch were varied significantly after acid-heat treatment, showing a synergy between acid and heat. Correspondingly, acid-heat treatment markedly changed gelatinization and pasting properties of rice starch by sharply decreasing gelatinization and pasting temperatures as well as pasting viscosities. Pearson correlation analysis was performed, showing that molecular weight, size, amylopectin chain length distribution, and amylose content were significantly correlated to gelatinization temperatures, and crystallinity was remarkably correlated to gelatinization enthalpy. As for pasting properties, molecular weight and size as the major factors were substantially correlated to pasting viscosities and pasting temperature. This study provides a structure-property correlation for acid-heat treated rice starch, giving scientific basis for the application of starch in food industry.