Relationship between alpha-glucosidase activity and physical and chemical properties of rice

To examine the relationship between a-glucosidase and the physical and chem ical properties of rice quality for human consumption, we measured a-glucos idase and two other saccharification enzyme activities and physicochemical properties of twenty-four kinds of milled rice originally harvested in 1997 . Koshihikari and Akitakomati (modern varieties) had higher alpha -glucosid ase activity than Akamai (Tsushima, local red rice) and Sinriki (old variet y). On the other hand, Akage (old variety) and Akamai (Tanegashima, local r ed rice) had higher a-amylase activity than Koshihikari. alpha -Glucosidase activity showed a negative correlation with starch-iodine blue value, tota l solid of residual liquid, expanded volume in cooking quality of milled ri ce (r=-0.542, r=-0.570, r=-0.460, respectively) and amylose content (r=-0.4 87). alpha -Glucosidase activity also showed a positive correlation with ma ximum viscosity and breakdown (r=0.557 and r=0.633, respectively) in pastin g properties of milled rice flours employing a Rapid Visco Analyser. These results suggested that the same activity was indirectly associated with eat ing quality. From the principal component analysis (PCA) for all examined m easurements, the first principal component represented amylose characterist ics and the second principal component represented reducing sugar character istics. The plot PCA defined by these two factors indicated amylose charact eristics, and also a chronological order of rice on the first principal com ponent. Moreover, alpha -glucosidase had a higher factor loading (0.778) on the first principal component, which suggests that alpha -glucosidase may be related to some parts of amylopectin synthesis.