2011 Volume 106 Issue 3 Pages 157-163
Miki (a traditional beverage in Amami Island) is not an alcoholic beverage in the Liquor Tax Act of Japan, because lactic acid fermentation is its main reaction. Interestingly, miki became an alcoholic beverage when shochu yeast was added from the early stage of preparing, forming ethanol. However, the rate of fermentation was slow and the fermentation ratio was also low. It is believed that the reason for this is the formed sugar is maltose because the main enzyme concerning saccharification was β-amylase in the raw sweet potato and maltose was the main product. Fermentation was retarded because shochu yeast could not utilize wort so efficiently. Therefore, shochu koji was added to convert the maltose into glucose. It was also found that shochu koji contains a high amount of α-glucosidase and converts maltose into glucose efficiently. The course of fermentation concluded satisfactorily with the addition of shochu koji. The formation of glucose from maltose was observed by HPLC. An improvement in the fermentation ratio was observed by the addition of shochu koji.
