qiita_sid_12448
Effect of sulfite addition and pied de cuve inoculation on the microbial communities and sensory profiles of Chardonnay wines: dominance of indigenous Saccharomyces uvarum at a commercial winery
The production of wine involves complex interactions between many microbial species and strains, and the microbial consortium of wine fermentations is also highly dependent upon winemaking decisions made at crush. To investigate how these decisions can affect the microbial communities and sensory attributes of commercially-produced wines, Chardonnay grape juice was allowed to ferment uninoculated, or was inoculated with a pied de cuve inoculum composed of vineyard-derived bacteria and fungi. Additionally, either 0 mg/L or 40 mg/L of sulfur dioxide (SO2) was added to the juice at crush. The bacterial and fungal communities of these wines were monitored using high-throughput amplicon sequencing (Illumina MiSeq), and Saccharomyces yeasts were identified to the strain level using microsatellite analysis. After fermentation, the wines were evaluated by a panel of wine experts to determine any differences in sensory profiles among treatments. When no SO2 was added at crush, the wines underwent alcoholic fermentation and malolactic fermentation simultaneously. Tatumella bacteria were also present in significant numbers only in the barrels to which no SO2 was added. These bacteria are likely responsible for the malolactic fermentation observed in the no-SO2 treatments and are reported here for the first time in North American wine fermentations. Additionally, all fermentations were dominated by indigenous Saccharomyces uvarum, and 150 unique S. uvarum strains were identified, with differences in strain composition as a result of SO2 addition. Wines that did not receive SO2 at crush were rated more fruity and less acidic than wines that received SO2. Wines receiving SO2 were considered to have less-desirable traits such as earthy and sulfur aroma/flavour. The pied de cuve inoculum had a limited effect on the microbial community, and only persisted when no SO2 was added; these wines did not fully complete alcoholic fermentation, and were rated to be higher in body and sweetness, and lower in acidity, than the other wines. This is the first report of indigenous S. uvarum strains dominating and completing alcoholic fermentation at a commercial winery in North America. For provenance files, R scripts, and raw data please visit: https://osf.io/kxqrn/