• Food Science and Preservation
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• v.23 no.5
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• pp.666-672
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• 2016

The objective of this study was to evaluate the effects of low temperature-adapted Saccharomyces cerevisiae Y297 and fermentation temperatures on the quality of Yakju brewed. Physicochemical properties of Yakju brewed were compared pH, total acidity, ethanol, free amino acid, organic acid contents, and volatile flavor compounds in S. cerevisiae Y297 with control treatment. Cooked non-glutinous rice and saccharogenic amylase in koji were mixed with ethanol-producing yeasts and then fermented at $15^{\circ}C$, $20^{\circ}C$, and $25^{\circ}C$ for 20 days. Yakju brewed using the Y297 treatment showed the highest ethanol yield (17.9%) at $20^{\circ}C$. Expression of heat shock protein (HSP) 104 was evaluated by immunoblotting as an indication of adaptation to low temperatures ($15^{\circ}C$); levels of the HSP104 protein were higher in the Y297 treatment than in the control. Organic acid analysis showed that the lactic acid content of Yakju brewed using the control was the highest at $25^{\circ}C$. Finally, free amino acid analysis showed that the Y297 treatment had a higher proportion of essential amino acids than the control. Overall, these results indicate that S. cerevisiae Y297 could be used as a suitable yeast for Yakju brewed under low temperature ($15^{\circ}C$) condition.

• Journal of Microbiology and Biotechnology
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• v.20 no.12
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• pp.1702-1710
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• 2010

Korean traditional rice wines yakju and takju are generally brewed with nuruk as the source of the saccharogenic enzymes by natural fermentation. To improve the quality of Korean rice wine, the microorganisms in the nuruk need to be studied. The objective of this research was to improve the quality of Korean wine with the wild-type yeast strains isolated from the fermentation starter, nuruk. Only strain YA-6 showed high activity in 20% ethanol. Precipitation of Y89-5-3 was similar to that of very flocculent yeast (>80%) at 75.95%. Using 18S rRNA sequencing, all 10 strains were identified as Saccharomyces cerevisiae. Volatile compounds present in yakju were analyzed by gas chromatography-mass selective detector. The principal component analysis (PCA) of the volatile compounds grouped long-chain esters on the right side of the first principal component, PC1; these compounds were found in yakju that was made with strains YA-6, Y89-5-3, Y89-5-2, Y90-9, and Y89-1-1. On the other side of PC1 were short-chain esters; these compounds were found in wines that were brewed with strains Y183-2, Y268-3, Y54-3, Y98-4, and Y88-4. Overall, the results indicated that using different wild-type yeast strains in the fermentation process significantly affects the chemical characteristics of the glutinous rice wine.

• Journal of Food Hygiene and Safety
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• v.26 no.1
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• pp.64-69
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• 2011

Steamed rice is usually used as an essential ingredient when Takju or Yakju is brewed in Korea. Alternatively, non-steamed rice can be used to keep thermolabile nutrients and fresh tastes richer in Takju or Yakju. In this study, therefore, the physicochemical properties (ethanol and sugar contents, pH, total acidities, and turbidities) and the fermentative microbial profiles (aerobic mesophillic bacteria (AMB), fungi, lactic acid bacteria (LAB), acetic acid bacteria (AAB), and Escherichia coli and coliforms) have been compared among 4 Takju and 1 Yakju samples brewed using steamed or non-steamed rice. Yakju brewed using non-steamed rice has approximately 2-3 times higher ethanol and sugar contents than other 4 Takjus brewed using steamed or non-steamed rice. The pH and total acidity values of all the 5 samples ranged 3.77-4.30 and 0.12-0.35, respectively. As for turbidities, Yakju brewed using nons-teamed rice was transparent, but other 4 Takjus were not. The AMB and fungal counts for Yakju brewed using nons-teamed rice were approximately $10^4$-fold less than those for 4 Takjus. The LAB counts for Takju and Yakju brewed using non-steamed rice were $10^3$-fold less than those for Takjus brewed using steamed rice. The AAB counts ranged $2-6\;log_{10}\;CFU/mL$ for all the 5 samples. E.coli and coliforms were not detected. Overall, there was no significant difference in microbial counts among 4 Takjus brewed using steamed or non-steamed rice, but Takju has higher microbial counts than Yakju. All the 5 samples were conclusively considered to be hygienically brewed and processed containing plenty of beneficial microorganisms.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.2
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• pp.281-286
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• 2014

This study was carried out to develop Yakju, a new kind of Korean traditional rice wine added with bamboo ethanol extract and characterized by containing various health benefits. The wine with bamboo ethanol extract was fermented by adding ginger and pear to improve flavor and quality. Several quality characteristics and physiological functionalities of Yakju were investigated. When bamboo ethanol extract was added to Yakju, the pH level decreased compared to that of the control. However, total acidity and soluble solid levels were higher than those of the control. The alcohol content of Yakju added with bamboo ethanol extract was slightly higher than that of the control. In examining the colors of Yakju containing bamboo ethanol extract, L value was lower than that of the control, whereas b value and brownness were higher. Various organic acids such as citric acid, malic acid, succinic acid, lactic acid, and acetic acid were determined, and the main organic acid among them was lactic acid. Various free sugars such as sorbitol, glucose, and fructose were detected and glucose was the most abundant. Total polyphenol content of Yakju added with bamboo ethanol extract was lower than that of the control. Further, electron-donating ability ranged from 23.8~40.0%, which was higher than that of the control. Nitrite scavenging ability of Yakju added with bamboo ethanol extract ranged from 15.2~36.4%, which was higher than that of the control at pH 6.0. Sensory evaluation of Yakju showed that bamboo ethanol extract+ginger as well as bamboo ethanol extract+ginger+pear treatment significantly increased flavor, taste, and overall acceptance compared to the others.

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.4
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• pp.521-527
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• 2008

Acanthopanacis cortex extracts added Yakju was manufactured and then fermentation and quality characteristics of Yakju were examined. Acanthopanacis cortex extracts added Yakju showed totally similar characteristics with the non-extract added Yakju of control groups. The pH showed almost no change to pH 4.0 after 6 days of fermentation and it was decreased only once in only fermentation time of 3 days. The acidity of Acanthopanacis cortex extracts added group showed no difference to the control group. The sugar obrix and reducing sugar content showed decrease in all two groups in the initial fermentation stage; however, it showed slow decrease as the late fermentation stage. The Acanthopanacis cortex extracts added Yakju showed less alcohol content than the control group in the initial fermentation stage. However, after 6 days of fermentation, the Acanthopanacis cortex extracts added Yakju showed more alcohol contents and constant increase till the final fermentation day. The pH, acidity, reducing sugar and alcohol content showed rapid changes between fermentation days 0 through 3. Therefore, it means that the Acanthopanacis cortex extracts added Yakju fermentation actively takes place between the days 0 through 3. Organic acids detected in Yakju were acetic, lactic, oxalic, malic and succinic acids. The acetic acid was the highest among the total acid contents. Eleutheroside E and chlorogenic acid, known as the effective components of Acanthopanacis cortex, showed stable status without changes in component content till stage two fermentation. The contents of eleutheroside E and chlorogenic acid were $7.61\pm0.39{\mu}g/mL$ and $3.63\pm0.18{\mu}g/mL$ on the final fermentation day, respectively. The fusel oil was slightly detected in both groups with values of $0.08\pm0.001{\sim}0.86\pm0.03mg%$ in n-propyl alcohol, isobutyl alcohol and isoamyl alcohol content. The Acanthopanacis cortex extracts added group was similar to the control group in the overall sensory test.

• Korean Journal of Food Science and Technology
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• v.42 no.1
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• pp.69-74
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• 2010

Black garlic has recently received significant attention due to its various health functional properties, and there has been an increase in demand for its use as a functional food. This study was performed to determine the optimum concentration for the fermentation of black garlic yakju. In addition, the antioxidant activity of the fermented black garlic yakju was examined. The alcohol content in the black garlic yakju significantly increased for 6 days and the pH gradually increased as the concentration of black garlic increased. The reducing sugar content at each black garlic concentration was maximal when it was fermented for 24 hours, and then rapidly decreased at longer fermentation periods. The main organic acids were lactic, citric, malic and oxalic acid. Also, the lactic acid content increased as the concentration of the black garlic increased where as the content of other organic acids decreased. The total polyphenol content, ferric ion reducing antioxidant power (FRAP) activity and DPPH (1,1-diphenyl-2-picryl-hydrazyl) free radical scavenging activity of black garlic yakju increased as the concentration of black garlic increased. The sensory characteristics of fermented black garlic yakju were evaluated in terms of color, flavor, taste and overall acceptability, and the highest overall acceptability value was obtained for yakju containing a black garlic concentration of 1-3%. Therefore, the optimum concentration of black garlic was determined to be 1% for the production of high quality black garlic yakju.

• Korean Journal of Food Science and Technology
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• v.48 no.3
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• pp.223-230
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• 2016

We investigated the fermentation characteristics of yakju made with nuruk extracts. Alcoholic fermentation was performed in an incubator set at $25^{\circ}C$ for 14 days. The study results are as follows: the alcohol content of yakju made with modified nuruk (18.67%) was higher than that made with other nuruk extracts (14.80-17.50%). The pH value of this modified nuruk (4.13) was higher than that of traditional nuruk (3.70-4.00). The yakju containing modified nuruk showed the highest acidity (3.64 mL/10 mL), amino acidity (4.72 mL/10 mL), soluble solid ($1.20^{\circ}Bx$), and color difference (39.78). The concentration of organic acids in traditional nuruks was 212.25-312.97 mg/100 mL, whereas that in modified nuruk was 295.92 mg/100 mL. Nitrogen compound concentrations in modified nuruk (2285.89 mg/L) were 2-14 times higher than that in traditional nuruk. Nitrogen compound concentration and amino acidity are the physiochemical characteristics with the highest impact on off-flavor and browning of yakju. In order to reduce these unfavorable characteristics, material with a lower protein content should be used.

• Journal of the East Asian Society of Dietary Life
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• v.10 no.3
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• pp.190-199
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• 2000

Information about the processing method of additional starter can be found in the 39 traditional kinds of classical literature. The traditional of Yakju, was analyzed and classified according to classical literature consist of 105 items relating to starters on those compounded alcoholics. 105 selected items were distributed among 5 groups of alcoholic beverages: processing methods of starter, additional starters for sweet and alcoholics, additional starters for Kwahaju, and those additional function for quality and quantity to the periodical conversion of the processing method through four centuries.

• Korean Journal of Food Science and Technology
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• v.50 no.4
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• pp.400-406
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• 2018

Takju and yakju are traditional Korean alcoholic beverages that are prepared by fermentation of glutinous rice with nuruk, a cereal starter containing various bacteria, fungi, and yeast. In this study, physicochemical and microbial properties of a total of 12 commercial takju and yakju samples were analyzed; their pH, sweetness, and alcohol content were varied, depending on the type of alcohol, from pH 3.64-4.8, $5.1-24.8^{\circ}Bx$, and 4.6-18.5%, respectively. Microbial communities were analyzed with 16S rRNA amplicon sequencing using MiSeq system. At the phylum level, Firmicutes (86.2%) was the most dominant, followed by Proteobacteria (8.08%), Actinobacteria (2.56%), and Cyanobacteria (3.13%). Lactic acid bacteria, including Lactobacillus, Lactococcus, Leuconostoc, and Weissella were also frequently detected. Among eukaryotes, Saccharomyces cerevisiae was the most dominant in these samples.

• Applied Biological Chemistry
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• v.30 no.3
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• pp.272-277
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• 1987

The odor threshold and agreeability of aroma components in Korean Yakju were measured in Null-Yakju, 19% ethyl alcohol solution, $20^{\circ}C$ distilled water and $50^{\circ}C$ distilled water by 20 panels. The measurement of the odor threshold in Null-Yakju was as follows: Formal-dehyde 5ppm, acetaldehyde 20ppm, ethylacetate 30ppm, ethyl alcohol 5g/l, acetone 7ppm, diacetyl 0.2ppm, n-propanol 20ppm, iso-butanol 80ppm, iso-amyl alcohol 10ppm and dimethyl sulfide 2ppm were found. The most agreeability of amyl alcohol, ethyl alcohol and acetaldehyde were $80{\sim}350ppm$, $2.6{\times}10^4{\sim}1{\times}10^5ppm$ and $75{\sim}160ppm$.