A A C C   2 0 0 0   A n n u a l   M e e t i n g

Studies have establish that the amylose content of rice was the single largest determinant of its texture. It is directly proportional to cooked-rice hardness and inversely proportional to its stickiness. Yet all studies also showed that amylose did not tell the whole story. Although many different tests have been intensively explored and some have proved useful, they at best were indices, not determinants, of rice quality. There was one possible exception, insoluble amylose. In the 80s it was found that a fraction of rice starch stained blue with iodine and strongly correlated with the insoluble amylose of the parent rice and the texture of cooked rice. This showed: (a) what was being called amylose was not [hence the term "amylose-equivalent (AE)"] and (b) some unknown structural diversity in amylopectin had probably more to do with rice texture than amylose. It has been shown that the proportion of chains length in amylopectin are different and high-amylose rices have greater amounts of long chains in their amylopectin and vice versa. Studies conclusively showed that the integrity, resilience and elasticity of the starch granules were directly proportional to the insoluble amylose and to the long chains of amylopectin. It was concluded that the long chains by their mutual interaction help build a strong and resilient starch granule and vice versa, which was the main factor behind the texture of cooked rice. Some questions, however, still remain as to the roles lipids, certain minerals, sugars and amino acids play in rice sensory quality.