Thermal and pasting properties of acid-treated rice starches

The physicochemical properties of acid-treated rice starches were investigated. Rice starches were treated with hydrochloric acid at different acid concentrations and hydrolysis times. The pasting properties were tested using a Rapid Visco Analyser, and gelatinization and retrogradation properties using a differential scanning calorimeter. The results showed that acid concentration had a more pronounced effect on degree of polymerization (DIP) and viscosity than hydrolysis time. The onset, peak and conclusion temperatures of gelatinization were increased significantly with hydrolysis time, while the gelatinization enthalpy (Delta H-G) was decreased. In addition, there was an increase in the gelatinization temperature range with longer hydrolysis time. After storing gelatinized starches at 4 degrees C for 7 days, the transition temperature and enthalpy (Delta H-R) to melt retrograded amylopectin did not change significantly. Additionally, the temperature and enthalpy transition for melting amylose-lipid complex of all gelatinized and retrograded starches were in the same range.