Biocontrol using Torulaspora delbrueckii in Sequential Fermentation: New Insights into Low Sulfites Verdicchio Wines

Torulaspora delbrueckii showed renewed interest in recent years in the fermentation of wine, for its biotechnological potential linked to the ability to enhance flavor and aroma and it probably is the non-Saccharomyces yeast currently widely used in winemaking. On the base of this, sequential fermentations with a selected native strain of T. delbrueckii (DiSVA 130) and low sulfite native strain of Saccharomyces cerevisiae (DiSVA 709) were carried out to establish their contribution in biocontrol and aroma profile. A first set trials, carried out in winery, were set up to establish the effect of the sulfur dioxide addition on pure and T. debrueckii/S. cerevisiae sequential fermentations. A second set of sequential fermentations without SO2 addition were conducted in the same conditions, to evaluate the biocontrol and aromatic effectiveness of the T. delbrueckii native strain and a commercial one. The effective biocontrol action of native T. delbrueckii inoculated in sequential fermentation was shown, indeed without SO2 addition the presence of native T. delbrueckii revealed an effective fungistatic action in the first two days of fermentation. Moreover, the native T. delbrueckii strain seems to have fermentative performances comparable to those of T. delbrueckii commercial strain showing a more evident biocontrol action (wild yeasts reduced by c.a. 1 Log at 2nd day) and its presence did not negatively affect S. cerevisiae fermentation activity. Finally, the combination of both native and commercial T. delbrueckii/S. cerevisiae trials led distinctive aromatic profile of wines with a significant enhancement of isoamyl acetate, phenyl ethyl acetate, supported by positive appreciations, from the tasters, for ripe and tropical fruits, citrus and balance. The whole results indicate that the proposed strain could be a potential biocontrol tool toward wild yeasts in the first phase of fermentation also contributing to improve and differentiate the final aroma wine.