• Mycobiology
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• 제42권4호
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• pp.353-360
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• 2014

Makgeolli is a traditional Korean alcoholic beverage. The flavor of makgeolli is primarily determined by metabolic products such as free sugars, amino acids, organic acids, and aromatic compounds, which are produced during the fermentation of raw materials by molds and yeasts present in nuruk, a Korean fermentation starter. In this study, makgeolli was brewed using the wild yeast strain Saccharomyces cerevisiae Y98-5, and temporal changes in the metabolites during fermentation were analyzed by ultra-high-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry. The resultant data were analyzed by partial least squares-discriminant analysis (PLS-DA). Various metabolites, including amino acids, organic acids, sugar alcohols, small peptides, and nucleosides, were obviously altered by increasing the fermentation period. Changes in these metabolites allowed us to distinguish among makgeolli samples with different fermentation periods (1, 2, 3, 6, 7, and 8 days) on a PLS-DA score plot. In the makgeolli brewed in this study, the amounts of tyrosine ($463.13{\mu}g/mL$) and leucine ($362.77{\mu}g/mL$) were high. Therefore, our results indicate that monitoring the changes in metabolites during makgeolli fermentation might be important for brewing makgeolli with good nutritional quality.

• Journal of Microbiology and Biotechnology
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• 제25권2호
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• pp.217-226
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• 2015

Metabolite profiles of seven commercial vinegars and two traditional vinegars were performed by gas chromatography time-of-flight mass spectrometry with multivariate statistical analysis. During alcohol fermentation, yeast, nuruk, and koji were used as sugars for nutrients and as fermentation substrates. Commercial and traditional vinegars were significantly separated in the principal component analysis and orthogonal partial least square discriminant analysis. Six sugars and sugar alcohols, three organic acids, and two other components were selected as different metabolites. Target analysis by ultra-performance liquid chromatography quadruple-time-of-flight mass spectrometry and liquid chromatography-ion trap-mass spectrometry/mass spectrometry were used to detect several metabolites having antioxidant activity, such as cyanidin-3-xylosylrutinoside, cyanidin-3-rutinoside, and quercetin, which were mainly detected in Rural Korean Black raspberry vinegar (RKB). These metabolites contributed to the highest antioxidant activity measured in RKB among the nine vinegars. This study revealed that MS-based metabolite profiling was useful in helping to understand the metabolite differences between commercial and traditional vinegars and to evaluate the association between active compounds of vinegar and antioxidant activity.

• Korean Journal of Food Science and Technology
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• 제48권1호
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• pp.48-53
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• 2016

The objective of this study was to evaluate the accuracy and efficiency of different methods used for the fermentable sugar assay in the production of Makgeolli sul-dut. In the initial stage of fermentation, Ipguk treatment produced a higher alcohol content compared to the Nuruk treatment. However, the alcohol content was not significantly different between the two starters at the final stage of fermentation. Acidity in the Ipguk treatment was higher than that of Nuruk throughout the fermentation period. After analyzing the fermentable sugars using dinitrosalicylic acid (DNS), Fehling's method, refractometer, glucose kit, and high performance liquid chromatography (HPLC), it was confirmed that the HPLC method was the most accurate for fermentable sugar quantification. In both types of starters, DNS and Fehling's methods showed results comparable to HPLC in terms of fermentable sugar content, while the glucose kit and refractometer analyses showed relatively large discrepancies, indicating that the Fehling's method could also be effective for the analysis of fermentable sugars in the manufacture of Makgeolli.

• The Korean Journal of Food And Nutrition
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• 제28권5호
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• pp.835-848
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• 2015

In the past, Korea had many kinds of jeupjang (succulent jang), a rapidly maturing original Korean jang (fermented soybean paste) of which there is no record in Chinese cookbooks. However, this local delicacy has almost been forgotten. Therefore, we looked for information about jeupjang in cookbooks written prior to the Joseon Dynasty in Korea (1392~1910) and in the 1950s. Among the recipes, there were 34 jeupjangs prepared with vegetables, such as eggplant and cucumber, and 9 without. The main ingredients of jeupjang are soybean, bran (wheat crust), and barley, and wild wheat is also used. Jeupjang is made in small portions to expedite its rapid maturation, but the most common form is egg-shaped, and there is also a flat or round, hilt-shaped version. In most cases, jeupjang consists of a mixture of meju powder (moldy soybean), water, and salt. Other ingredients can include nuruk (moldy bran), bran, wheat flour, an alcoholic beverage, maljang (dried fermented soybeans), ganjang (liquid soy sauce), malt, and takju (Korean murky wine). Jeupjang meju can be fermented in a vessel, most widely in baskets made of straw (sum and dungumi) or willow or interwoven twigs (chirung), but jars can also be used. The leaves of the paper mulberry are generally used for the mat and cover, but straw or leaves of the sumac, mulberry, or pine tree, soy, and fallen leaves are also used. Unlike other jangs, jeupjang is matured at $60^{\circ}C$ to $65^{\circ}C$, using heat emitted from the decomposition of horse dung, haystacks, or manure. Jeupjang became defunct or was transformed into jeomjang, jiraejang, mujang, paggeumjang, makjang, jipjang, and tojang. These jangs differ from jeupjang in that they use rice, malt, or hot pepper powder.

• Food Science and Preservation
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• 제20권4호
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• pp.564-572
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• 2013

We investigated the quality characteristics of brewing brown rice vinegar through a traditional static fermentation process. Accordingly, we decided to compare the physicochemical characteristics of brewing vinegar at different temperatures and filtration methods. In four to five weeks' time, the acetic acid fermentation exhibited the highest titratable acidity and then it eventually decreased. The titratable acidity was affected by the filtration method. It was revealed that the titratable acidity was higher in the forced filtration than the traditional filtration method. Various organic acids were detected in order to initialize the fermentation stage and as the fermentation progressed, only the acetic acid could be detected. The total free amino acid content was higher at a temperature of $30^{\circ}C$ than at $20^{\circ}C$. Moreover, the free amino acid content was dependent on the acetate content during the acetic fermentation process. The main bioactive substance of the ${\gamma}$-aminobutyric acid content was more than twice at a fermentation temperature of $30^{\circ}C$ compared to the fermentation temperature of $20^{\circ}C$. Furthermore, the total amino acid and essential amino acid content at a temperature of $30^{\circ}C$ was excellent. The quality of the brown rice vinegar via forced filtration method at a temperature of $30^{\circ}C$ was the most excellent. Based on these results, the fermentation temperature and the use of nuruks (fermenting agent) affected the quality of the brown rice vinegar, and an appropriate method to consider its purpose is required.