• Korean Journal of Food Science and Technology
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• v.46 no.1
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• pp.25-32
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• 2014

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 $18.0{\pm}0.6%$, whereas soju made using nuruk reached $14.3{\pm}1.7%$. The level of succinic acid was the highest in ipguk soju ($7,685.33{\pm}34.97$ ppm), but nuruk soju also showed a high level of succinic acid ($5,945.79{\pm}76.30$ 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 ($80^{\circ}C$ and $90^{\circ}C$). 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 $90^{\circ}C$ 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.

• Korean Journal of Food Science and Technology
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• v.46 no.6
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• pp.694-701
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• 2014

This study aimed to investigate the aging of liquor brewed with fermented wine using ipguk (koji) in a jar (JA) and stainless steel container (SC), which are generally used in Korea, and to review the characteristics of the liquors as a function of aging time. The initial alcohol content was 39.8-40.9%, and gradually decreased in the JA and SC as the aging time increased. In the case of fusel alcohols, the n-propanol, isobutanol, and isoamyl alcohol contents did not increase with increasing aging time, in the cases of both JA and SC. The A/B (isoamyl alcohol/isobutyl alcohol) ratio was similar under reduced pressure (RP) and atmospheric pressure (AP), at 1.32-135. The A/P (isoamyl alcohol/n-propanol) and B/P (isobutyl alcohol/n-propanol) ratios were 2.17-2.22 and 1.62-1.68, respectively. During the early stages of distillation, under RP, the isoamyl alcohol content was the greatest, followed by isobutyl alcohol and ethyl palmitate. Under AP, the isoamyl alcohol content was the greatest followed by decanoic acid, ethyl palmitate, and isobutyl alcohol. The highest sensory score under RP, 60 cmHg, was $6.98{\pm}0.28$.

• Korean Journal of Food Science and Technology
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• v.45 no.6
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• pp.714-720
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• 2013

We investigated the brewing and fermenting characteristics of makgeolli produced from high-yielding rice varieties. We used the high-yielding indica rice varieties, Anda and Dasan 1, and the japonica varieties, Deuraechan and Boramchan. Our results showed that the rice protein level was the highest in makgeolli produced from Anda ($7.5{\pm}0.2%$), while the amylose level was the lowest in makgeolli produced from the mid- to late-maturing japonica varieties (Deuraechan, $18.9{\pm}0.7%$; Boramchan, $18.9{\pm}1.4%$). Samples of makgeolli produced from Anda, Deuraechan, and Boramchan by using the Ipguk (Koji) method had an alcohol content of 16.6-17.4% on completion of fermentation. By contrast, makgeolli produced from Dasan 1 had an alcohol content of 14.3%; further, the makgeolli differed significantly in the sensory test and was scored as excellent regarding comprehensive preference. For makgeolli produced by using the uncooked rice fermentation method, samples produced from the indica varieties, Anda and Dasan 1, had lower alcohol contents (17.2% and 17.0%, respectively) and higher total acidity levels (0.33% and 0.31%, respectively) than did samples produced from the japonica varieties, Deuraechan and Boramchan (0.28% for both). In the sensory test, samples produced from Anda and Dasan 1 performed significantly better regarding scent, swallowing, and comprehensive preference.