Effect of millimeter waves on the microbiological and physicochemical properties of Korean rice wine Makgeolli.

Millimeter waves are electric waves between 30 and 300 GHz. They are known to affect microbial growth. Here, the effects of millimeter waves on the microbiological and physicochemical properties of Makgeolli irradiated during fermentation were investigated. Millimeter waves at 60 and 70 GHz were used, and the fermentation was carried out at 30°C. The numbers of both lactic acid bacteria and yeasts have changed with similar pattern each then during the fermentation, but the effect of milimeter wave treatment was not critical as growth patterns were independent of both irradiation period and wave frequency. Furthermore, pH and total acidity did not change during fermentation. Although irradiation drastically increased sugar production during the initial stage of fermentation, the change was not frequency dependent. At the end of fermentation, the alcohol content in irradiated Makgeolli was definitely higher than that in un-irradiated Makgeolli, and the difference was frequency dependent.