糯米の〓化現象に関する実験 : 第1報 異る乾燥条件が〓化の発現に及ぼす影響

抄録

In glutinous grains of some cereals, it is observed that glassy ton of grain colour changes into the milky white as the desiccating proceeds. This phenomenon has been called the "Ryokka". In this experiment, the authors examined how the phenomenon was affected by different desiccating conditions which consisted of twenty series combining both different temperatures and relative humidities as shown in Table I. The glutinous rice variety named Taisyo-moti was used. Main results were as follows : 1) The higher desiccating temperatures reduced water contents of grains more rapidly to the lower equilibrium of it than the lower temperature did, when the relative humidity was kept constant. On the other hand, in the case of constant temperature, lower humidities showed more rapid decrease of water contents than higher ones, being followed by the lower equilibrium as well as in the former case. 2) Under a certain definite temperature condition, it depends merely upon the grade of relative humidity whether the Ryokka phenomenon happens in glutinous grains or not. In other words, the higher the desiccating temperature was, the higher humidity made the milky white appearance in grains. At the lowered temperatures, the lower humidity must be necessary for the phenomenon. The limits of humidity corresponding to the temperature were as those : 70°C.……85%, 50°C. ……82%, 30°C. ……71.5%, 10°C. ……25% 3) The higher desiccating temperatures made water contents of grains lower at the time the Ryokka happened, in contrasts to the comparatively higher water contents at the lower temperatures (Table 2). That is, at higher temperatures glutinous grains need the greater extent of drying for the phenomenon and vice versa. This fact is very interesting, but the reason remains to be solved.