Co-fermentation with Pichia kluyveri increases varietal thiol concentrations in Sauvignon Blanc

Background and Aims: Volatile varietal thiols are one class of yeast metabolite that add aroma/flavour to Sauvignon Blanc, particularly to the Marlborough style from New Zealand. While various strains of Saccharomyces cerevisiae are known to liberate such thiols, there are no data examining whether non-Saccharomyces species effect concentrations of these thiols in wine. Methods and Results: We screened a variety of New Zealand wine yeast isolates and found some that were able to liberate either 3-mercaptohexan-1-ol (3MH) or 3-mercaptohexyl acetate ( 3MHA). We show that co-fermentation with specific commercial strains and an isolate of Pichia kluyveri from New Zealand, at a 1: 9 starting ratio, significantly enhances the 3MHA concentrations in Sauvignon Blanc compared with single species ferments. Conclusions: Co-fermentation with this isolate of P. kluyveri may provide a means to elevate 3MHA concentrations in Sauvignon Blanc; the mechanism behind this increase is unknown. Significance of the Study: Techniques that allow the predictable manipulation of varietal thiols potentially provide tools for winemakers to alter wine style without the use of genetically modified organisms.