Effect of Heat Moisture Treatment Using Different Solvents and Incubation Times on Resistant Starch Formation of Rice Flour

The thermal and pasting properties and Resistant Starch (RS) formation of high amylose rice flour were investigated at 121°C using different solvents and storage times. The samples treated with water and lactic acid 10 mmol/L with storage times 0, 24, 48 and 72 h had the highest degree of gelatinization, ranging from 98.64 to 99.86%. The samples treated with ethanol and lactic acid 10 mmol/L (in ethanol) had degrees of gelatinization varying between 58.25 and 59.91%. For the study on the thermal properties, the onset temperature (T_o), peak temperature (T_p), conclusion temperature (T_c) and enthalpy (ΔH) of resistant starch preparation (retrograded rice flour) using water and lactic acid 10 mmol/L were not observed, but those of heated flour using ethanol and lactic acid in ethanol (10 mmol/L) were detected. The endothermic peaks of the amylose-lipid complex and resistant starch were also observed at higher temperatures from the Differential Scanning Calorimeter (DSC), with no effect of treatments on T_o, T_p and T_c. Rice flour heated in water and then stored for 24 h showed a favorable effect on formation of RS at 10.80%. Significant reductions were observed in all Rapid Visco Analyzer (RVA) viscosities of the retrograded rice flours.