무증자 발아흑미를 이용한 막걸리 제조 시 온도가 미치는 영향

Abstract

In this study we investigated the effect of temperature on the two-stage fermentation of Makgeolli using uncooked germinated black rice. The fermentation processes were conducted at <TEX>$15^{\circ}C$</TEX> for three weeks and <TEX>$25^{\circ}C$</TEX> for 7 days. The pH of Makgeolli at <TEX>$25^{\circ}C$</TEX> increased from pH3.0 to pH 4.2, which was consistent with that at <TEX>$15^{\circ}C$</TEX>. In contrast total acidity of Makgeolli at <TEX>$15^{\circ}C$</TEX> was about half of that at <TEX>$25^{\circ}C$</TEX> (0.36% and 0.59%, respectively). By the 7 days-fermentation at <TEX>$25^{\circ}C$</TEX>, 11% of alcohol was produced, whereas three weeks were required for the same alcohol production at <TEX>$15^{\circ}C$</TEX>. In the case of sugar contents, the amounts of total glucose-equivalent reducing sugars and glucose increased at the end of the fermentation at <TEX>$25^{\circ}C$</TEX> up to 2.25 mg/mL and 3.4 mM, respectively, whereas those at <TEX>$15^{\circ}C$</TEX> were maintained at very low levels (0.18 mg/mL and 0.1 mM, respectively). Such limited supplement of sugars at <TEX>$15^{\circ}C$</TEX> seemed to affect metabolism of yeast, resulting in different composition of organic acid. At <TEX>$25^{\circ}C$</TEX>, citric acid that was 73.4 ppm at the initial fermentation was consumed completely, whereas 20 ppm of citiric acid was remained at <TEX>$15^{\circ}C$</TEX>. In addition, acetic acid and lactic acid in Makgealli at <TEX>$15^{\circ}C$</TEX> were 53% and 14% of those at <TEX>$25^{\circ}C$</TEX>.