Abstract
Japonica-type rice grains stored at 40°C for 2 months were treated with a freeze-dried powder of acetic acid bacteria and then cooked. It was found that the originally existing n-hexanal were decreased by more than 35%. Moreover, the stale flavor had been signiticantly reduced compared to that of non-treated rice grains. Simultaneous treatment with freeze-dried cells of the acetic acid bacteria and a surfactant was 1.3-1.9 times more effective for reducing the amount of n-hexanal than with the cells of acetic acid bacteria alone. The optimum conditions for reducing the stale flavor were investigated by using a combination of the acetic acid bacterial cells and the surfactant. The optimum conditions were as follows : soaking temperature, 50°C ; soaking time, 30-180 min ; pH 4.5-7.0, optimally at pH 6.0. Treating Indica-type rice grains with the freeze-dried cells of acetic acid bacteria was also effective for reducing the specific off-flavor of the rice.
