Studies on Alkali Decomposition of Rice Kernel : 1. On the alkali test of milled white rice kernel

[摘要] Method and some experimental conditions of an alkali test were investigated in December 1963 through observations and tests on the disintegration of milled white rice kernels in dilute alkali solution. Ten milled rice kernels of duplicated samples collected from the 1963 crop, were treated in 20 ml of potassium hydroxide solution in a covered Petri dish, and laid in a room temperature regulated at 20±0.5°C. After 24-hour treatment, the degrees of kernel decomposition were evaluated in accordance with a descriptive scale (Table 1). Ventral and inner portions of kernel were less resistant to alkali as compared with the other portions of kernel. And, in the course of kernel decomposition, bursting of ventral side and turning of endosperm tissue inside out were observed (Fig. 1) in the most of japonica and some of indica varieties. So, a new 10-grade decomposition index (Table 1) considering the abovementioned decomposition features was used in this experiment to show the degree of kernel disintegration. And minute differences in the decomposition were discerned clearly by this index, especially for the japonica varieties. On the optimum concentration of KOH test solution, a clear difference between jappnica and indica varieties was revealed. And 1.4 to 1.5 % and 1.7 to 1.8 % solution of KOH seems to be suitable for japonica or easily decomposable varieties and indica or alkali resistant varieties respectively (Fig. 2). In case of usually milled rice kernels, under or over-milling in slight extent did not considerablly affect the decomposition degree of the kernels, though scaring of bran layer in the initial stage of milling process abruptly decreased the alkali resistibility and abnormally high milling revealed a progressive susceptibily to alkali in the inner layers of endosperm tissue (Fig. 3). Gracks formed in the milled kernels increased the decomposition values of the kernels (Table 2).

[学科分类] 农业科学（综合）