Physicochemical and Microbial Properties of Korean Traditional Rice Wine, Makgeolli, Supplemented with Cucumber during Fermentation

Korean traditional rice wine, Makgeolli, has been widely consumed with increasing popularity in Korea. Also, there has been an increase in the varieties of Makgeolli for the younger generation. In this study, we examined the physicochemical and microbial properties of Makgeolli supplemented with cucumber during fermentation. Four hundred grams of cucumbers (20% of the total amount of rice) were grinded and added to the rice solution (2 kg rice and 3.12 L distilled water) along with the Nuruk (40 g) and yeast (14 g). After mixing the solution, it was fermented for six days in a water bath ($28^{\circ}C$). During the fermentation, the pH value of the cucumber Makgeolli fell from 5.88 to 3.94 on day-1, and steadily increased to a pH value of 4.48 by day-6. The total acidity of the cucumber Makgeolli sharply increased from 0.02 to 0.20% on day-1, and then slowly increased thereafter to 0.28% by day-6. After the 6-day fermentation, the L values of the control and the cucumber Makgeolli were similar. The total viable cell, lactic acid bacteria and yeast count of the control and the cucumber Makgeolli increased considerably after the 6-day fermentation process. Free sugar analysis showed that glucose contents decreased with increasing fermentation periods. The succinic acid content was the highest among all the organic acids. Thirty-nine volatile compounds were observed on the final day of fermentation in the cucumber Makgeolli.

오이를 첨가한 막걸리의 발효기간 중 이화학적 및 미생물학적 특성

본 연구에서는 오이를 첨가한 막걸리의 특성을 알아보기 위하여 쌀의 20%만큼 오이를 첨가하여 막걸리를 제조한 후 이화학적 및 미생물학적 특성을 평가하였다. 발효 6일째 알코올 함량은 대조군 16.3%, 오이 막걸리 16.2%로 유의적인 차이가 없었으며, 발효 6일째 두 시료의 pH도 차이가 나타나지 않았다. 총산은 두 시료 모두 발효 1일째에 급격히 증가하고, 그 이후 완만히 증가하였다. 총 균수, 유산균수 및 효모수 모두 오이 막걸리가 대조군보다 높았으며, 색도는 대조군과 오이 막걸리 사이에 큰 차이가 나타나지 않았다. 유리당 중 glucose는 발효가 진행되면서 감소하였고, 대조군과 오이 막걸리 모두 succinic acid 함량이 가장 높았다. 휘발성 화합물 중 오이 막걸리에서 가장 많이 동정된 성분은 3-methyl-1-butanol, 2-methyl-1-propanol, ethyl acetate이었다.