Studies on Alkali Decomposition of Rice Kernel : 2. Effects of varieties and some ripening conditions on alkali decomosition of milled white rice

[摘要] Alkali tests on which the author have reported in the previous paper, were conducted during December 1963 on the milled kernels of 124 rice varieties from 1963 crop. Effects of air temperatures shading and nitrogen application in ripening period were also investigated in relation to alkali digestibility. Most of indica varieties showed their stronger resistibility to alkali than japonica varieties as was already reported by many researchers. Shape of kernel had no clear relation to alkali digestibility in the case of japonica varieties. In indica rice, however, some varieties of big breadth-thickness ratio were less resistant than narrow-grain varieties. Glutinous kernels showed no substantial differences from nonglutinous ones, suggesting that amylose content of kernel had little effect on alkali digestibility of rice kernel. kernels of late season varieties which ripened in low temperature were more digestible rather than early or midseason varieties ripened in hot or warmer season. High temperature (30°C) treatments in ripening periods considerably increased alkali resistance of rice kernels. Shading treatments in the same periods and heavy nitrogen application just prior to heading decreased alkali resistance of kernels. It is considered therefore that environmental conditions which accelerate the development of kernels may increase their alkali resistance through denaturization of synthesizing starch and structural strengthening of endosperm tissues. Green kernels and injured kernels such as milky-white kernels which obsuructed thier ripening by some in jurious causes and kernels collected from kernel-attaching position of inferion strength such as the second kernel from the top on each panicle branch were more digestible as compared with normal kernels and kernels from vigorous positions. Alkali digestibility of milled rice kernel is thought to be mainly dependent upon the nature of endosperm starch being controled by hereditary characters as well as environmental conditions.

[学科分类] 农业科学（综合）