The Qualities of Liquor Distilled from Ipguk (koji) or Nuruk under Reduced or Atmospheric Pressure

Abstract

Abstracts This study aimed to analyze the general ingredients and volatile compounds of ipguk (koji) and nuruk soju distilled under reduced pressure (RP) or atmospheric pressure (AP) conditions. After the secondary brewing process, soju made using ipguk had a final fermentation alcohol content of 18.0±0.6%, whereas soju made using nuruk reached 14.3±1.7%. The level of succinic acid was the highest in ipguk soju (7,685.33±34.97 ppm), but nuruk soju also showed a high level of succinic acid (5,945.79±76.30 ppm) after its final fermentation. In an analysis of fusel alcohol content, the level of n-propanol in ipguk soju (389.10-397.27 ppm) was similar under different RP (50 cm Hg and 60 cm Hg) and AP conditions (80°C and 90°C). Under RP and AP conditions, the isoamyl alcohol/isobutanol (A/B) ratio was similar, ranging from 1.32-1.35. In ipguk soju distilled under RP conditions of 50 cm Hg and 60 cm Hg, the amount of the toxic component, acetaldehyde, was 8.59 and 9.27 ppm, respectively. Under AP conditions, the amount of acetaldehyde in ipguk soju distilled at 80 and 90 o C was 9.80 and 10.63 ppm, respectively, indicating that the amount of acetaldehyde did not differ depending on the distilling method used. These results suggest that the liquor distilled from the mash produced using ipguk under RP conditions may be of a higher quality.

Characterization of brewing microorganisms isolated from Korean traditional nuruk for Cheongju production

“…The synthesis of ester and higher alcohols was significantly higher in the mash prepared with Y190 compared with the other mashes. These results strongly suggest that fermentation with the yeast Y190 and A. oryzae 83-10 during the preparation of Cheongju had a positive effect on increasing aroma compounds such as ester and higher alcohols, reported by Cho et al [26] and Lee et al [6].…”

“…This tendency was also observed at other fermentation temperatures (20, 25, and 30°C). The Cheongju prepared with Y190 received high sensory scores due to the enhanced ester and higher alcohols concentration as Lee et al [6] reported. There were no differences with regard to sensory evaluation between the control, Y263, and Y270.…”

“…There are two types of nuruk, namely, the Korean traditional nuruk prepared with whole flour in which various microorganisms grow naturally and the improved nuruk prepared with sterile cereal in which pure culture mold is artificially propagated [4,5]. The traditional nuruk results in lack of uniformity during fermentation and a deficiency of saccharification power (SP) but provides variety in quality because of various microorganisms [6,7]. So et al [8] reported the characteristics of modified nuruk prepared by inoculation and cultivation of Rhizopus japonicus T2, Aspergillus oryzae L2, and Hansenula sp.…”