Chiang Mai Journal of Science

     This study aimed to investigate the effect of microwave and infrared heating on increasing the resistant starch content (RS) and reducing glycemic index (GI) of RD 43 rice (Oryza sativa L.). First, in the microwave heating process, the sample was heated by microwave power at 400–800 W for 15–45 s. It was found that rice heated at 600 W had the highest RS (0.41 ± 0.09%) and the lowest predicted glycemic index (pGI) (52.38 ± 0.26). In terms of time, heating for 30 s caused the highest RS (0.40 ± 0.14%) and heating for 30 and 45 s caused the lowest pGI (52.70 ± 0.39 and 52.82 ± 0.30, respectively). A higher RS was obtained under microwave heating at 600 W for 30 s (0.44 ± 0.01%) and 45 s (0.50 ± 0.05%) and a lower pGI was obtained under microwave heating at 600 W for 15 s (52.23 ± 0.11) and 30 s (52.31 ± 0.23). Second, in the infrared heating process, the sample was heated by infrared power at 400–800 W for 120–180 s. The result showed that the effect of power and time had signifi cant effects on digestible starch (DS), total starch (TS), RS and pGI. The infrared heating at 600 W for 150 s caused a higher RS (0.45 ± 0.16%) and lower pGI (50.4 ± 0.57) and that the TS, DS and RS were not signifi cantly different (p < 0.05). These fi nding might be a useful tool to produce the low GI rice, which provided a benefi cial nutrients and health.