• Food Science and Preservation
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• v.30 no.6
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• pp.1029-1042
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• 2023

This study aimed to apply the technology of increasing the volatile aromatic compounds in wine through mixed fermentation of Saccharomyces cerevisiae and non-Saccharomyces yeasts to make distilled soju. The expectation was to induce changes in metabolites such as volatile aromatic compounds before the distillation process, followed by concentrating these compounds through distillation to enhance the odor property of distilled soju. Additionally, the study aimed to examine the impact of mixed fermentation with S. cerevisiae and non-Saccharomyces yeasts on distilled soju's free amino acid content. As a result, when Hanseniaspora uvarum yeast was used, there was an increase in the content of low molecular weight volatile aroma compounds, particularly esters. Distilled soju co-fermented with S. cerevisiae and H. uvarum SJ69 exhibited similar amino acid content to distilled soju single-fermented with S. cerevisiae. However, distilled soju co-fermented with S. cerevisiae and H. uvarum S6, a decrease in amino acid content. Sensory evaluation results indicated a higher odor score in distilled soju co-fermented with S. cerevisiae and H. uvarum S6, suggesting that the mixed fermentation technology utilizing H. uvarum could contribute to improving the quality of distilled soju in the future.

• Food Science and Preservation
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• v.19 no.3
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• pp.433-437
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• 2012

The fusel oils and the volatile flavor compounds of two potato sojues, one of which was produced with the traditional distillation apparatus(soju-gori) and the other, with the reduced pressure distillation system, were examined. The fusel oil content was high in the potato soju that was distilled under reduced pressure (potato soju(II)). The relative ratio of the isoamyl alcohol to the isobutyl alcohol and the n-propanol was 3.1:0.8:1.0 in the potato soju that was distilled with soju-gori (potato soju(I)), and 4.0:1.2:1.0 in potato soju(II). The chromatograms of the volatile components apparently differed between potato soju(I) and potato soju(II). Potato soju(I) contained four kinds of alcohol, six kinds of ester, n-valeraldehyde, and acetic acid. Potato soju(II) contained seven kinds of alcohol, 14 kinds of ester, two kinds of aldehyde, acetic acid, and three other compounds. Potato soju(II) significantly scored higher for flavor property than potato soju(I).

• Food Science and Industry
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• v.52 no.4
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• pp.410-417
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• 2019

Soju is a traditional distilled spirit that may traced back to the 13th century, Koryo Dynasty in Korean Peninsula. It is the major distilled spirit consumed in Korea and it was considered Korea's most popular alcoholic beverage. Despite of the long history and popularity, its production manners have been limited developed in terms of distillation technology. In this article, a variety of distillation stills including batch pots and continuous columns are reviewed. Additionally, by introducing recent distillation technologies, Soju and distilled spirits related industry can apply the technologies on the product development for corresponding consumer's diverse needs.

• Korean Journal of Food Science and Technology
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• v.47 no.1
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• pp.51-55
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• 2015

Four varieties of the Korean sweet potato, Yeonmi, Jeungmi, Shincheonmi, and Shinyeulmi, were chosen to prepare the distilled koguma-soju (sweet potato-soju). The relationship between the flavor of the koguma-soju and the content of monoterpene alcohols (MTAs) was studied. The MTAs investigated here were linalool, nerol, geraniol, citronellol, and ${\alpha}$-terpineol. The ranges of MTA concentrations in the koguma-soju made from the four sweet potato varieties were $14.0-16.6{\mu}g/L$ for nerol, $24.8-34.7{\mu}g/L$ for linalool, $32.8-38.5{\mu}g/L$ for geraniol, $37.8-54.2{\mu}g/L$ for citronellol, and $76.6-94.7{\mu}g/L$ for ${\alpha}$-terpineol. Geraniol, nerol, and linalool were found in lower concentrations, while ${\alpha}$-terpineol was present in a higher concentration compared to their average content in the imo-shochu, a distilled Japanese sweet potato-soju. The concentrations of citronellol in the koguma-soju and imo-shochu were similar. The flavor evaluation tests revealed that the koguma-soju produced from the Yeonmi variety had a leafy vegetable or a grass-like, sharp flavor, whereas the Jeungmi-soju was characterized by a fruity or a sulfur-like sharp taste. Floral, vanilla-like, and mild flavors were predominant in the Shincheonmi-soju, while the Shinyeulmi-soju had either a fruity, citrus-like flavor or a rubber-like, rough taste. This study demonstrates that koguma-soju made from different sweet potato varieties have unique characteristic flavors.

• Korean Journal of Food Science and Technology
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• v.44 no.5
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• pp.648-652
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• 2012

The sensory characteristics of nine commercially distilled soju samples were determined by sensory descriptive analysis. Eight aroma attributes, as well as four flavor/taste attributes, and six mouth-feel related attributes were evaluated by 9 judges. The descriptive data set was initially analyzed for a significant overall product effect by employing a three-way mixed model analysis of variance (judges, samples, and replications) as well as two-way interactions, with judges treated as random. In addition, correlations between mean attribute ratings were calculated, and a principal component analysis (PCA) of the mean attribute ratings employing the covariance matrix was conducted. Based on the PCA, distilled soju samples were primarily separated along the first principal component, which accounted for 66% of the total variance between the samples, with high intensities of 'alcohol taste' and 'alcohol aroma' versus 'yeast aroma'. The second principal component accounted for 14% of the total variance. Soju containing high alcohol showed stronger intensities of 'bitterness', 'alcohol taste', 'alcohol aroma', as well as all mouth-feel attributes.

• Food Science and Preservation
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• v.30 no.4
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• pp.683-690
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• 2023

The study was conducted to confirm the possibility of producing alcohol beverages from Dae-hong peaches. Upon examining the quality characteristics of distilled soju using Dae-hong peaches, the alcohol content was 1.12 to 1.16 times higher than that from the atmospheric distillation method. Soju with 20 % peach extract content had the highest alcohol content and the lowest volatile acid content, indicating a low possibility of causing irritating odors. Acetaldehyde was 1.3-1.94 times lower in vacuum-distilled soju, and methanol was not detected in all samples. The absorbance value of furfural, a burnt component generated during distillation is high in atmospheric distillation, which can cause irritating odors. Upon examining the volatile fragrance components, isoamylalcohol and 1-propanol were found to be the main components, both of which were the highest in the treatment group with 20 % peach extract content. The electronic nose analysis revealed that this group showed the most opposing flavor patterns to the control group, and when distilled under reduced pressure with 20 % addition of Dae-hong peaches can produce high-quality soju.

• 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.49 no.5
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• pp.486-493
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• 2017

The purpose of this study was to compare the differences of seven distilled soju samples that were presented at the main stage of the 2015 Korean Liquor Contest. The characteristics of the awarded products and other products were compared. The general components of prize-winning soju showed that the total acidity (0.22%) and alcohol content (38.44%) were higher than other soju (0.10, 22.81%), and that these properties influenced various sensory properties. For the sensory characteristics and consumer preference factors, the descriptive analysis and consumer preference testing were conducted. The descriptive analysis revealed that the (aftertaste) bitterness, corn-silk odor, sake odor/flavor, and overall taste intensity were strongly expressed in the prize-winning distilled soju. For the preference analysis, various preferences, such as "flowery odor/flavor" and "rich odor/flavor" appear to have influenced the positive preferences and "too strong an odor/flavor", "aftertaste bitterness", and "sharp tasting" were found to have a negative effect on preference.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.466-473
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• 2018

The purpose of this study is to develop a distilled soju with high quality and stable brewing technology by analyzing the changes of general components and volatile components in the production of distilled soju by the use of fermentation agent such as koji and nuruk. White rice flour was used as a main raw material. White koji, yellow koji, traditional nuruk, and improved nuruk were used as a fermentation agent respectively. Also, yellow koji, traditional nuruk, and improved nuruk were added at a certain ratio to prepare white koji. The distillate was prepared by vacuum distillation and the quality characteristics were compared and analyzed. When the fermentation agent was used alone, the alcohol content was higher in the order of white koji, improved nuruk, yellow koji, and traditional nuruk. The initial acidity was higher than that of other fermentation agents and the highest alcohol content was found to be helpful for stable brewing. The highest content of higher alcohol was found in the yellow koji mash, and ethyl acetate was the highest in the traditional nuruk. When the fermentation agents were mixed, there was no difference in the alcohol content between $1^{st}$ fermentation mash and $2^{nd}$ fermentation mash. On the other hand, the content of higher alcohol was increased with the increase of the input ratio of yellow koji, and it decreased with the increase of the ratio of traditional and improved nuruk. It is expected that it will be possible to manufacture various distilled soju with different flavor and aroma if the yellow koji and the traditional nuruk are appropriately used based on the white koji having excellent fermentation characteristics and it will be very helpful for improving the stability and quality of brewing.

• Korean Journal of Food Science and Technology
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• v.49 no.4
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• pp.369-376
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• 2017

Maturation of distilled spirit can generate diverse flavors and tastes. Rice Soju was matured in oak casks (MSO) and stainless steel containers (MSS) for one year at ambient temperature. Ipguk (Aspergillus luchuensis) and Saccharomyces cerevisiae Y88-4 were used, and reduced pressure ($110{\pm}20Torr$) distillation was applied to brew Soju. Acidity and conductivity were increased in both MSO and MSS. MSO reduced alcohol content (from 43 to 40%) and volume (from 18,000 to 12,730 mL), and significantly altered yellowness (from 0.2 to 30.2). Furthermore, MSO increased the isoamyl alcohol (from 276.7 to $339.2{\mu}g/mL$) and isobutyl alcohol (from 122.3 to $144.2{\mu}g/mL$) content. Gas chromatography-mass spectrometry was used to detect volatile compounds in Soju, which included 20 esters, 7 alcohols, 2 acids, and 5 miscellaneous compounds. Oak lactone was detected only in MSO and was considered as a specific flavor component associated with oak maturation. Thus, maturation materials contribute to the physicochemical property of distilled spirits.