본 연구는 발효조건을 달리한 현미 막걸리의 술덧성분 변화를 조사하였다. 서로 다른 발효제와 발효온도에 따른 알코올의 차이는 $30^{circ}C$ 발효가 $20^{circ}C$보다 알코올 도수가 평균 2% 정도 높은 것으로 나타났다. 당화력 차이는 발효 초기부터 $20^{circ}C$보다 $30^{circ}C$ 발효액의 당도가 높게 나타난 것으로 보아 알코올 도수에도 영향을 미치며, pH는 발효 4일까지는 서서히 감소하였고 그 이후, 변화의 폭은 크지 않았다. 적정산도는 발효가 끝날 때까지 지속적으로 증가하였으며, $20^{circ}C$ AK의 적정산도가 가장 높게(0.57%) 나타났고, $30^{circ}C$ 발효 술덧에서는 0.66%로 산패 가능성은 없었다. 색도 중 L 값과 a 값은 발효초기의 모든 술덧에 비해 발효 종료시점에 조금 낮아지며, b 값은 발효가 진행됨에 따라 꾸준히 상승하였다. 발효 술덧의 유기산은 총 9종이 검출되었으며, 그 중 citric acid 함량이 가장 높게 나타났다. Lactic acid는 오히려 $20^{circ}C$ 발효술덧에서 더 많이 검출된 것으로 보아 발효온도에 따라 생성된 유기산이 차이가 있었다. 유리아미노산 함량은 발효제 종류 및 발효온도에 따라 크게 차이가 있었고, 유리아미노산은 $20^{circ}C$보다 $30^{circ}C$ 발효 술덧에 많이 있었다. 이상의 결과를 살펴보면, $30^{circ}C$에서 제조한 현미 막걸리가 더욱 우수한 품질을 가지며, 누룩 종류 및 발효온도에 따라서 현미 막걸리의 주질이 결정된다. 향후, 농가형 흑초 제조에 적합한 현미 막걸리의 술덧 제조가 가장 중요하다고 여겨진다.
In this study we investigated the possibility of preparing brewed brown rice makgeolli, a traditional Korean rice wine, under diverse conditions. For this purpose the physicochemical characteristics of makgeolli brewed at different temperatures, utilizing a variety of nuruks, the traditional Korean fermentation agent, were studied. The alcohol content was seen to be highest when brewing occurred at $30^{circ}C$, with the nuruk TN producing 16.2%. At $20^{circ}C$TN produced 14.1% alcohol content. The alcohol content was therefore higher, by about 2%, for $30^{circ}C$ fermentations than $20^{circ}C$ fermentations. Similarly, saccharifying activity was influenced by temperature and sugar content, with a higher activity seen at $30^{circ}C$ than at $20^{circ}C$. As the fermentations progressed acidification petered out, with titratable acidity being 0.50-0.67% in all end samples. On the Hunter L, a, b scale; the a value decreased slightly, while the b value increased steadily during the fermentation process. Measurements of total organic acids were highest at $30^{circ}C$, with the nuruk AK, at about 550 mg%. The content of citric acid was the highest at $30^{circ}C$, being 230-310 mg% in all samples. However, more lactic acid was detected at $20^{circ}C$ than at $30^{circ}C$. Total free amino acid was highest at $30^{circ}C$, with TN at $8,605{mu}g/ml$, AK at $6,083{mu}g/ml$, and RJ at $2,381{mu}g/ml$. Total free amino acid and essential amino acid was shown to be higher at $30^{circ}C$ than at $20^{circ}C$. The bioactive substance ${gamma}$-aminobutyric acid was also higher at $30^{circ}C$, with TN at $223{mu}g/ml$. From all of these results, we surmise that brown rice makgeolli manufacturing conditions are optimal at $30^{circ}C$ fermentation temperatures and using the nuruk TN for brewing vinegar. In addition, the nuruk used clearly affects the quality of brown rice makgeolli and an appropriate method to determine the best nuruk for various purposes should be pursued.
