Influence of wine components on pellicle formation by pellicle-forming yeasts

This study aimed to clarify differences in susceptibility to red wine pellicle formation by pellicle-forming yeasts between two wine grape cultivars and to investigate wine components affecting pellicle formation. Twenty wines each of Muscat Bailey A (MBA) and Merlot (MR), the major grape cultivars of Japanese red wine, were used. Pellicle formation occurred more often in MBA wines than in MR wines, and almost all MBA wine surfaces were covered with pellicle after incubation for five days. Principal component analysis revealed the relationships between pellicle formation and the concentrations of ethanol, phenolics and tannins. The mean concentration of tannins in the pellicle MR wines (436 mg/L) was significantly lower than that in the non-pellicle MR wines (660 mg/L). Furthermore, the mean concentration of tannins in MBA wines (139 mg/L) was also significantly lower than that in MR wines (570 mg/L). Wine grape cultivar having a low concentration of tannins may be highly susceptible to pellicle formation by pellicle-forming yeasts during winemaking.

Isolation and Investigation of Potential Non-Saccharomyces Yeasts to Improve the Volatile Terpene Compounds in Korean Muscat Bailey A Wine

The Muscat Bailey A (MBA) grape, one of the most prominent grape cultivars in Korea, contains considerable amounts of monoterpene alcohols that have very low odor thresholds and significantly affect the perception of wine aroma. To develop a potential wine starter for Korean MBA wine, nine types of non-Saccharomyces yeasts were isolated from various Korean food materials, including nuruk, Sémillon grapes, persimmons, and Muscat Bailey A grapes, and their physiological, biochemical, and enzymatic properties were investigated and compared to the conventional wine fermentation strain, Saccharomyces cerevisiae W-3. Through API ZYM analysis, Wickerhamomyces anomalus JK04, Hanseniaspora vineae S7, Hanseniaspora uvarum S8, Candida railenensis S18, and Metschnikowia pulcherrima S36 were revealed to have β-glucosidase activity. Their activities were quantified by culturing in growth medium composed of different carbon sources: 2% glucose, 1% glucose + 1% cellobiose, and 2% cellobiose. W. anomalus JK04 and M. pulcherrima S36 showed the highest β-glucosidase activities in all growth media; thus, they were selected and utilized for MBA wine fermentation. MBA wines co-fermented with non-Saccharomyces yeasts (W. anomalus JK04 or M. pulcherrima S36) and S. cerevisiae W-3 showed significantly increased levels of linalool, citronellol, and geraniol compared to MBA wine fermented with S. cerevisiae W-3 (control). In a sensory evaluation, the flavor, taste, and overall preference scores of the co-fermented wines were higher than those for the control wine, suggesting that W. anomalus JK04 and M. pulcherrima S36 are favorable wine starters for improving Korean MBA wine quality.