Effects of Heat-moisture Treatment on Glycemic Index and Relevant Indexes of Glutinous Rice Flour

In this study, the heat-moisture treatment was used to decrease the glycemic index (GI) value of glutinous rice flour, and then relevant indexes were compared with those of other treatments. Based on the influence of moisture content, temperature and treatment time on amylose content and digestion characteristics of glutinous rice flour, the single factor ranges were determined, and then the Box-Behnken design was used to optimize the heat-moisture treatment process with amylose content (which is significantly negative correlation with GI value) as a crucial index. Finally, the in vitro digestion characteristics and GI value of glutinous rice flour obtained by optimal heat-moisture treatment process (HMT), by ordinary process (WR), and only by enzymatic hydrolysis process (ER) respectively were compared to investigate the influence on GI value and other relevant indexes. The optimum heat-moisture conditions were: The treatment time was 2.3 h, the temperature was 116 ℃, and the moisture content was 20%. Under the optimum heat-moisture treatment conditions, the amylose content was 3.62%±0.01%, and it was confirmed that the average measured value was consistent with the theoretical value (3.62%), indicating that the model could be used to optimize the heat-moisture treatment process of glutinous rice flour. Compared with WR, the content of rapidly digestible starch and hydrolysis index were decreased significantly, and the contents of slow digestible starch and resistant starch were increased obviously, and GI value decreased by 30.1% in HMT. Taken altogether, the glutinous rice flour prepared by this heat-moisture treatment method had a relatively low GI value, which could provide experimental reference for the further development of low GI glutinous rice flour.