Effect of dry heat treatment on physical property and in vitro starch digestibility of high amylose rice starch

The influence of dry heat treatment (DHT) of high amylose rice starch was investigated on starch digestibility and physical properties and their characteristics were compared through the PCA analysis. High amylose rice starch was prepared by DHT under different temperatures (110, 130, and 150 °C) and times (0, 1, 2, and 4 h). The gelatinization temperature and enthalpy decreased as temperature and time increased, revealing the change of semi-crystalline region. There were significant increases in gel strength and pasting viscosity above 130 °C, whereas gel strength and pasting viscosity were reduced with increasing heating time. On in vitro starch digestibility of DHT starch gel, the rapidly digestible starch and predicted glycemic index of DHT starches were lower than those of native starch. Both the lowest predicted glycemic index and the highest gel strength was observed at 130 °C for 1 h. In the results of PCA analysis, the heating temperature was negatively correlated with in vitro starch digestibility as well as pasting viscosity and gel strength. These results demonstrated that DHT could be useful of enhancing the physical and nutritional properties of high amylose rice starch.