Early fermentation volatile metabolite profile of non-Saccharomyces yeasts in red and white grape must: a targeted approach

Saccharomyces cerevisiae is the main driver of alcoholic fermentation. It is typically inoculated at high levels to ensure successful implantation as well as reduce the risks of stuck fermentations and off-flavor production. However, winemakers have found that wines produced with only S. cerevisiae can be lacking in complexity compared to fermentations where non-Saccharomyces yeasts are more active. This study sought to understand the early fermentation characteristics of Kazachstania gamospora, Lachancea thermotolerans, Metschnikowia pulcherrima, Torulaspora delbrueckii and Zygosaccharomyces kombuchaensis in both Sauvignon blanc and Syrah musts. S. cerevisiae was used as a control. Solid-phase microextraction coupled to GC–MS was used to evaluate the musts once they reached 2% ethanol concentration. The method targeted 90 different compounds known to occur in wine and/or be produced by yeast during fermentation. For the first time, K. gamospora and Z. kombuchaensis have been studied in the context of wine. While the other yeasts are commercially available starter cultures, they have never been profiled this extensively. Analysis showed that each yeast profile was unique and different based on the must. The non-Saccharomyces yeasts produced lower concentrations of esters, alcohols and terpenes with the exception of K. gamospora which produced more total esters than the control.