Effect of the inoculation strategy of non-Saccharomyces yeasts on wine malolactic fermentation

Interest in some non-Saccharomyces yeasts has increased recently, because they have been associated with an improvement in wine quality. Nevertheless, little attention has been paid to the effect that the use of these yeasts may have on malolactic fermentation (MLF). In this study, the strains Torulaspora delbrueckii Biodiva and Metschnikowia pulcherrima Flavia were evaluated by co-inoculation and sequential fermentation with S. cerevisiae QA23. A fermentation with S. cerevisiae as a single starter was also performed as a control, then MLF was performed inoculating Oenococcus oeni PSU-1 in all wines. Finally, the wines obtained after alcoholic fermentation and MLF were characterised. The results of the coinoculated fermentations were similar to those of the S. cerevisiae control fermentations. Nevertheless, significant differences were observed in sequential fermentations in terms of lower content of acetic, L-malic and succinic acids. These differences were particularly noticeable in fermentations carried out with T. delbrueckii.