Managing wine quality using Torulaspora delbrueckii and Oenococcus oeni starters in mixed fermentations of a red Barbera wine

The use of selected starter cultures for grape must fermentation is nowadays practiced in most wine regions of the world, and as the range of available microorganisms increases this gives winemakers the possibility to increase biodiversity in guided fermentations. Nevertheless, little information is available regarding the oenological use of Saccharomyces and non-Saccharomyces yeasts in combination with lactic acid bacteria. The present study evaluates the effect of the inoculation of a non-Saccharomyces yeast, Torulaspora delbrueckii, in an alcoholic fermentation (in combination with a Saccharomyces starter), together with different modalities of malolactic fermentation management (co-inoculation, sequential inoculation and no inoculation of an Oenococcus oeni starter), on the quality of a red Barbera wine. The fermentation dynamics were verified and the final wine properties were evaluated in terms of physico-chemical composition determined by ¹H-NMR, free volatile compounds measured by GC-MS and organoleptic characteristics assessed via sensory analysis. Overall, the results show that the joint employment of non-Saccharomyces yeasts did not delay alcoholic nor malolactic fermentation progress, did not interfere with the positive effect of the co-inoculation of malolactic bacteria (beneficial for both fermentation length and for the chemical, aromatic and sensory properties of wine) and enabled the production of wines with a more intense colour.