Abstract
The effect of β-amylase in sweet potato on rice and rice gruel cooked with sweet potato, called imomeshi and imogayu, was studied by measuring the chemical properties and by sensory tests. A crude enzyme extract from sweet potato (ESP) was used as the cooking water. The amount of reducing sugars, especially maltose, in the rice and rice gruel cooked with ESP was larger than that when cooked with water alone. It was found that β-amylase in ESP degraded the starch in the rice grains to maltose. Rice gruel contained a larger amount of reducing sugars than cooked rice, regardless of the cooking water used. This seemed to result from differences in the time-course characteristics of the cooking temperature and from the ratio of cooking water to rice grains. The degradation of starch seemed to occur to the inner endosperm as well as to the outer layer. Sensory tests indicated significantly higher sweetness in both the cooked rice and rice gruel cooked with ESP than in the samples cooked with water.
