Effects of Cultivar and Cultivation Region on Endosperm Enzyme Activity Involved in the Palatability of Cooked Rice

摘要

The endosperm enzyme activity of rice is thought to vary depending on various parameters such as cultivar type, storage conditions, and cultivation region. Focusing on the variation in enzyme activity, we examined the relationship between these parameters and the palatability of cooked rice. To improve measurement convenience, rapidity, substrate specificity and sensitivity, enzyme activity was assessed using synthetic substrates. The following enzymes were examined and subjected to chemometric analysis : alpha- and, beta-amylases; alpha-glucosidase; beta-glucanase; beta-galactosidase; alpha-rnannosidase: and beta-xylanase. The results indicated that the endosperm enzyme activities differed among cultivars closely related to Koshihikari, namely, activities of alpha- and beta-amylase and beta-galactosidase differed significantly between cultivars. "Pirouette" multivariate analysis software was used to perform principal component analysis and thereby group cultivars according to endosperm enzyme activity. Haenuki was grouped closely to Koshihikari, whereas Kirara 397 was distantly related to Koshihikari. We were able to correlate carbohydrate-related enzyme activity with the characteristics of the cultivars.