Differences in grape-surface yeast populations significantly influence the melatonin level of wine in spontaneous fermentation

Abstract

The grape surface harbors a complex of yeast communities, many of which are responsible for wine fermentation, thus impacting wine quality. Although the ability of a single yeast strain to produce melatonin has previously been reported, it is not clear whether yeasts on the surface of regional grapes can modulate melatonin levels in local wine. In this work, yeasts on the surface of Vitis vinifera L. cv. Merlot grapes were used to activate alcohol fermentation. Thirteen yeast species were identified, and significant differences in melatonin levels were observed among the fermented samples of distinct grape-surface microbes. Melatonin levels peaked at an early stage of fermentation, and the highest level was observed in Ningxia-Y samples. Obvious differences were observed in the capacity to produce melatonin among yeast strains derived from the different regions, even though some of them were the same species. Furthermore, mixed fermentation with non-Saccharomyces strain, that possess high melatonin-producing ability, significantly increased melatonin levels in wines. In general, our results showed that differences in yeast population of grape-surface could significantly influence the melatonin levels in local wines.