Physicochemical and Mochi-making Properties of the Native Red and Black-Kerneled Glutinous Rice Cultivars

Abstract

The physicochemical and mochi-making properties of native red and black-kerneled glutinous rice (RKGR) and white-kerneled glutinous rice (WKGR) of japonica and indica varieties, were examined. In both the japonica and indica varicties, RKGR cultivars contained more protein than WKGR cultivars, the difference being 2.1% and 1.9%, respectively. In both varieties, no significant difference in amylose contents of RKGR and WKGR was observed. The amylographic characteristics of RKGR varied considerably with the variety. In the japonica variety, RKGR cultivars tended to have higher mean maximum viscosity and breakdown values than WKGR cultivars, although the difference was not significant. By contrast, in the indica variety, the mean maximum viscosity and breakdown values of RKGR cultivars were significantly (p<0.05, t-test) lower than those of WKGR cultivars. In both varieties, the difference in gelatinization temperature between RKGR cultivars and WKGR cultivars was not significant. Cooked RKGR cultivars had a higher hardness and a higher hardness/adhesion ratio than WKGR cultivars, although a significant difference between the adhesion of RKGR cultivars. The hardening speed of mochi made from RKGR cultivars tended to be lower than that of mochi made from WKGR cultivars. The hardening speed of mochi showed a significant positive correlation, with the atmospheric temperature during the ripening period. The palatability of mochi of RKGR cultivars in both varieties tended to be inferior to that of WKGR cultivars. The particularity of physicochemical and mochi-making properties of RKGR cultivars is considered to be excellent as the processing material and to develop new processed-rice products.