Effect of amylose content on structure, texture and α-amylase reactivity of cooked rice

- Explore the relationship between the structure and α-amylolysis of cooked rice.
- Explore the relationship between the texture and α-amylolysis of cooked rice.
- The appearance of internal hollows in cooked rice with different amylose content.

The susceptibility of cooked rice to α-amylolysis were studied in four Taiwanese rice cultivars differing in amylose contents, i.e. Taichung Native 1(TCN1, indica), Taigung 9 (TG9, japonica), Taichung Sen Waxy 1 (TCSW1, indica waxy), and Taichung Waxy 70 (TCW70, japonica waxy). In addition, the correlation between α-amylolysis and the microstructure and textural properties of the four rice cultivars was investigated. The hardness, gumminess and chewiness of cooked rice followed the order of TCN1>TG9>TCSW1>TCW70. However the waxy rice cultivars showed a higher extent and rate of α-amylolysis. Using scanning electron microscopy, the microstructure revealed that the low-amylose rice and waxy rice cultivars contained hollow in the central endosperm. The internal hollow disappeared after α-amylolysis, indicating that α-amylase had penetrated the cooked grain, resulting in the inside-out hydrolysis. These results indicated that the textural properties of cooked rice are influenced mainly by its amylose/amylopectin ratio, followed by influencing the pattern of α-amylolysis.