High temperature treatments to control sugar consumption by yeasts during makgeolli fermentation

Abstract

This study aimed to control sugar consumption during makgeolli fermnetation using high temperature treatments after 3 days of fermentation at normal temprature. makgeolli fermentation was performed at 25°C for the initial 3 days and at 34, 37, 40, and 43°C, respectively, for the next 4 days. When fermented at 25°C (control), the alcohol content increased up to 16.5%; however the alcohol content of makgeolli treated at elevated temperatures reduced by 13.8 %. In the control group, typical saccharification and fermentation proceeded simultaneously, and the reducing sugar content remained low due to sugar consumption by active yeast. However, at high fermentation temperatures, the nuruk enzymes functioned normally and saccharification proceeded well; however the conversion of fermentable sugars to alcohol was inhibited, possibly due to a decrease in yeasts activity. The viable cell count of yeasts was 4-6 log CFU/mL regardless of the fermentation temperature. These results indicate the possibility of producing sweet live-yeast makgeolli without the addition of artificial sweeteners through a temperature-controlled makgeolli fermentation.