Estimation of hardening speed of 'mochi' of glutinous rice from the gelatinization temperature, an amylographic characteristic, and the correlation of the hardening speed with gelatinization temperature and air temperature during the ripening period

摘要

We examined the correlation of hardening speed of "mochi" (rice cake) of glutinous rice with the gelatinization temperature, an amylographic characteristic, and air temperature during the ripening period, in six glutinous rice cultivars. The hardening speed of "mochi" showed a strong negative correlation with the gelatinization temperature in all cultivars examined. Thus, it is possible to use gelatinization temperature as an indicator of the hardening speed of "mochi". When the gelatinization temperature was lower than 62degreesC, the hardening speed of "mochi" was as low as 1.0, which is not suitable for "mochi" processing. Therefore, the gelatinization temperature of 62degreesC was suggested to be useful as an indicator for selecting glutinous rice cultivars superior in "mochi" hardening speed. Air temperature during the ripening period showed a strong negative correlation with the hardening speed of "mochi", and a strong positive correlation with the gelatinization temperature. When the air temperature during the ripening period was lower than 24degreesC, the hardening speed of "mochi" was very slow. The hardening speed varied with the year more widely than with the cultivar, suggesting that the hardening speed of "mochi" is affected more largely by the air temperature during the ripening period than by genetic background.