Abstract
We measured the chewing properties of cooked rice from six new characteristic rice cultivars, Saikai 194, Saikai 198, Hokuriku 149, Suigen 258, Hoshiyutaka and Saikai 184, using a rheometer and analyzed their relation to the starch molecular structures reported previously (Mizukami et al., Oyo Toshitsu Kagaku, 43, 15-23 (1996)). The cultivars revealed different chewing properties: the hardness, adhesiveness and stickiness were 590-940 g, 440-5700 erg and 55-200 g, respectively. Hoshiyutaka and Saikai 184 were hard, less adhesive and sticky, whereas Hokuriku 149 was soft and Saikai 194 was strongly adhesive and sticky. These chewing properties were compared with the amylose content and molecular structures of amylose and amylopectin, and a correlation to the molecular structure of amylopectin was found; that is, hard cooked rice and less-sticky and adhe-sive cooked rice had large amounts of very-long chains in the amylopectin molecules. The very-long chains might restrain the collapse of starch granules by crosslinking amylopectin molecules because starch with a low breakdown had a large amount of the very-long chains, and thus may be one of the causes of the hardness of the cooked rice.
