Spontaneous fermentation of raisin water to form wine

Yeast obtained from the water containing raisins has been conventionally used for breadmaking. It is assumed that people consumed naturally fermented raisin water as wine in ancient times. In this study, we demonstrated spontaneous fermentation by yeast that colonizes raisins. Raisin water samples containing Saccharomyces and non-Saccharomyces species underwent alcohol fermentation. As the fermentation progressed, the diversity and abundance of Aspergillus decreased. A significant difference in β diversity was detected between the microbiomes of raw grapes and raisins, with raisins containing a higher ratio of Saccharomycetaceae. The yeast colonizing raisin fermented alcohol more efficiently than those on raw grapes. Outdoor-dried raisins harbored a distinct eukaryotic microbiome that successfully fermented alcohol, indicating that these yeasts migrate from the environment. Therefore, our data suggest that sun-drying grapes can be utilized for food preservation and making alcoholic beverages, validating the ancient practice of wine-making from raisins due to spontaneous fermentation.