Textural Properties and Structures of Starches from Indica and Japonica Rice with Similar Amylose Content

The difference in stickiness between cooked Nipponbare (Japonica rice) and Khao Dawk Mali (indica rice) that have similar apparent amylose content was investigated, and the fine structure of starch in both cooked rice and extract from the surface of cooked rice was analyzed. Non-sticky high-amylose rice (Indica rice) was also studied for comparison. The solid content and amount of amylopectin in the extract from the surface of cooked Nipponbare were the highest, followed by cooked Khao Dawk Mali, and cooked high-amylose rice. This difference in solid content and the amount of amylopectin contributed to the stickiness of cooked Nipponbare. This suggests that the stickiness of cooked rice is less when less amylopectin is dissolved into cooking water, even when the amylose content and fine structure of the starch in the rice grains is similar. Thus, cooked Khao Dawk Mali is less sticky than cooked Nipponbare, despite having similar amylose content.