Abstract
Yakju, a traditional fermented beverage in Korea, is prepared using various raw materials and methods, and, hence, exhibits various characteristics. Low-temperature-fermented yakju can inhibit the growth of undesirable bacteria and is known for its unique flavor and refreshing taste. To increase the production of volatile aromatic compounds in yakju, strains with strong resistance to low temperatures and excellent production of volatile aromatic compounds were screened from indigenous fruits (grape, persimmon, plum, aronia, wild grape) and nuruk in Korea. One Saccharomyces cerevisiae and three non-Saccharomyces strains were finally screened, and yakju was fermented at 15 °C through mono/co-culture. The analysis of volatile aromatic compounds showed that S. cerevisiae W153 produced 1.5 times more isoamyl alcohol than the control strain and reduced the production of 2,3-butanediol by a third. Similarly, a single culture of Pichia kudriavzevii N373 also produced 237.7 mg/L of ethyl acetate, whereas Hanseniaspora vineae G818 produced ~11 times greater levels of 2-phenethyl acetate than the control. Alternatively, Wickerhamomyces anomalus A159 produced 95.88 mg/L of ethyl hexadecanoate. During principal component analysis, we also observed that the co-culture sample exhibited characteristics of both volatile aroma compounds of the single cultured sample of each strain. Our results suggest that yakju with unique properties can be prepared using various non-Saccharomyces strains.
Highlights
Yakju is a genre of traditional Korean fermented liquor fermented with rice as the primary ingredient
A total of 661 isolates were used in this experiment, which were isolated from indigenous fruits and nuruk owned by the Microbial Biotechnology Laboratory, Department of Food Science and Biotechnology, Kyungpook National University (Daegu, Korea)
Low-temperature fermentation prevents bacteria-dependent spoilage and preLow-temperature fermentation prevents bacteria-dependent spoilage and preserves serves flavor; this method produces a different aroma component profile flavor; this method produces a different aroma component profile that from that observed with room temperature fermentation
Summary
Yakju is a genre of traditional Korean fermented liquor fermented with rice as the primary ingredient. It is characterized by a clean and intrinsic flavor by removing solids through filtration at the end of fermentation. Studies have reported that yeast in a low-temperature fermentation environment is influenced by several factors, such as protein transcription, cell membrane fluidity, RNA structure stability, and enzyme activity, as well as aroma component-related reactions [5,6]; when low-temperature fermentation is performed using a low-temperature-resistant strain, it is possible to prevent spoilage and create yakju with a unique profile [7].
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