Experiments were carried out to elucidate the cooking properties of Thai rice (Oiyza sativa L. var. indica) comparing with those of Japanese rice, Chiyonishiki (Oryza sativa L. var. japonica, cultivar, Chiyonishiki). The effect of cooking with pressure cooker on improving palatability of Thai rice was also determined.
Amylose content of Thai rice was higher (28.6%) than that of Chiyonishiki, on the other hand its water absorption rate during soaking was lower. These rices were cooked with regular cooker and with pressure cooker adding various amount of water. The amounts of added water for Thai rice cooked with regular cooker were 1.5,1.6 and 1.9 times (added water weight/rice weight). The amount of added water for Chiyonishiki and for Thai rice cooked with pressure cooker was 1.5 times each. On hardness and stickiness measured by a texturometer as to the cooked rice with regular cooker, the hardness of Thai rice was harder than that of Chiyonishiki and its stickiness was less on cooking with the same added water. By adding more water to Thai rice up to 1.9 times, the hardness was nearly equal to that of Chiyonishiki, whereas its maximum stickiness was about 50% of that of Chiyonishiki. In case of cooking with pressure cooker, the stickiness of Thai rice by a texturometer was increased to about 70% of Chiyonishiki. Panel members judged Thai rice to be more preferable both texture and total quality than that cooked with regular cooker. On the observation of an ultrastructure by SEM, Thai rice cooked with regular cooker had less reticular structure in the surface area and poor networks in the cross section. By cooking with pressure cooker, it was observed that these structures were improved.