When uninoculated fermentation is used to make wine, Saccharomyces cerevisiae living on winery equipment and in the vineyards exert important influences on the fermentation. It has been unclear whether yeasts remain after the oak barrel is washed and uninoculated wine fermentation restarted. We prepared oak chips that were immersed in a fermentation mash with S. cerevisiae and（1） washed with water at an ambient temperature, washed with and soaked in（2） water at 80℃,（3） 50 mg/L sulfur dioxide solution, or（4） 30% ethanol solution. We then performed a fermentation test using sterilized grape juice and treated oak chips without yeast inoculation. Fermentation occurred except with the 80℃-treated chips. We next conducted an uninoculated fermentation test using fresh Chardonnay grape juice with or without oak chips that were washed with water after fermentation：S. cerevisiae and Hanseniaspora uvarum increased and finally reached the same percentages as those in a fungal species analysis using high-throughput DNA sequencing. After the fermentation of Chardonnay grapes, many ovoidal and lemon-shaped cells were observed on the oak chip surfaces. Our results thus demonstrated that wood surfaces such as oak chips provide an environment where yeasts can survive, and wood-resident yeasts can re-drive wine fermentation.

We investigated changes in the quality of sake stored at 0-35℃ for up to 6 months. Sake stored at 35℃ showed significantly high hineka intensity and a poor overall score, while no significant difference was observed between 15℃ and 0℃. DMTS and methional concentrations increased remarkably at 35℃ and were highly correlated with hineka intensity. Comparing average concentrations before and after 6 months of storage, differences were within 10% at 0℃, at 25℃ methional had almost doubled, and at 35℃ DMTS increased over 10 times. These results indicate that the favorable sake storage temperature is below 15℃ for quality preservation.

This study investigated the 4-vinylguaiacol（4-VG） production and the FDC1 and PAD1 genotype of sake brewing yeast strains isolated from the natural environment. None of the isolated strains exhibited any 4-VG production. The FDC1 and PAD1 sequences of these strains were homozygous, which are the same genotypes of the sake yeast used in modern sake brewing, which is the representative K-9. The 4-VG nonproduction of these strains was due to nonsense mutations detected in FDC1（c. 160A >T）. These data indicate that the FDC1 genotype is a useful marker to distinguish 4-VG production of sake brewing yeast.