Evaluating the impact of yeast co-inoculation on individual yeast metabolism and wine composition

[摘要] ENGLISH ABSTRACT: The use of non-Saccharomyces yeasts together with Saccharomyces cerevisiae in mixedstarter cultures has become an accepted oenological tool to enhance the organolepticproperties of wine. Recent studies have indeed demonstrated the positive contribution that non-Saccharomyces yeasts may have on the bouquet of wine. These mixed starter cultures arecharacterized by high inoculation levels of individual strains into the must, and each strain inturn is characterized by its own specific metabolic activity. These factors lead to a multitude ofinteractions occurring between the individual populations within the must. The fundamentalmechanisms which drive these interactions are still largely unknown, but several studies havebeen conducted in order to investigate the metabolic outcome of these interactions. In thisstudy, we endeavour to further characterize the interactions which occur between four individualnon-Saccharomyces yeast strains in mixed culture fermentation with S. cerevisiae.Metschnikowia pulcherrima IWBT Y1337, Lachancea thermotolerans IWBT Y1240, Issatchenkiaorientalis Y1161 and Torulaspora delbrueckii CRBO LO544 were used in mixed culturefermentations with a commercial strain of S. cerevisiae at an inoculation ratio of 10:1 (non-Saccharomyces: S. cerevisiae). The biomass evolution and fermentation kinetics of bothparticipating species were affected by the high cell density of the other, with neither populationreaching the maximal density attained by the pure culture fermentation. The final winecomposition of each individual mixed fermentation showed clear differences, from the purecultured S. cerevisiae and from each other, based on the concentrations of the major volatilecompounds found in the wine. Upon further characterization of these specific mixed culturefermentations, it was found that each individual combination of non-Saccharomyces and S.cerevisiae produced similar increases and decreases of certain major volatile compounds asdemonstrated by previous authors, using the same combination of non-Saccharomyces speciestogether with S. cerevisiae. From a winemaking perspective, the use of these non-Saccharomyces yeast strains in combination with S. cerevisiae could be a useful strategy todiversify the chemical composition of wine, by increasing the concentration of certain desirablevolatile compounds and by modulating the concentration of undesirable metabolites.Furthermore, this research serves as a foundation for further elucidation of the interactionswhich drive these metabolic outcomes in response to the high cell density of two yeastpopulations in mixed culture fermentations.

[发布机构] Stellenbosch University