Abstract
The relationship between the molecular structure of amylose and the texture of cooked rice was investigated using Korean rices (3 varieties of japonica type and 3 varieties of tongil type (japonica-indica breeding type)). The inherent viscosity and number-average degree of polymerization of japonica type amylose were lower than those of tongil type amylose. The fraction of molecular weight above 5 × 105 for japonica type amylose was 31.7-37.1% and that for tongil type amylose was 43.8-47.5%, indicating that molecular size of japonica type amylose was smaller than that of tongil type amylose. The content of hot-water soluble amylose and ratio of hot-water soluble amylose to total amylose of japonica type were higher than those of tongil type amylose. With the texture of cooked rice, japonica type had low hardness, high adhesiveness and high ratio of adhesiveness to hardness compared with tongil type. The inherent viscosity, number-average degree of polymerization and molecular weight size of amylose showed a positive correlation with hardness, but a negative correlation with adhesiveness of cooked rice. The results suggest that the molecular structure of rice amylose could be at least partly responsible for the texture of cooked rice.
