Bioprotective effect of non-Saccharomyces yeasts in wines made without SO₂

Abstract

The sulphur dioxide (SO₂) is the most widely used additive in the wine industry because of its preservative action. However, in recent years the number of wineries that produce wines without SO₂ has increased significantly because its allergenic character. The production of SO₂-free wines may lead to the development of different spoiling microorganisms, which could lead to wine deterioration. One of the strategies suggested to avoid wine spoilage, is the non-Saccharomyces yeast inoculation, which prevent bacteria development. The objective of this work was to evaluate the bioprotective effect of a mixed inoculum of non-Saccharomyces yeasts (Torulaspora delbrueckii and Lachancea thermotolerans 70/30) in two consecutive vintages (2018 and 2019). Three strategies were carried out in triplicate: spontaneous fermentation in sulphited must, spontaneous fermentation in non sulphited must and inoculated fermentation (non-Saccharomyces mixed inoculum) in non sulphited must. In all cases, after 72 hours of fermentation the vats were seeded with a commercial Saccharomyces cerevisiae yeast. The presence in the medium of lactic and acetic bacteria and the chemical composition of the wines were evaluated. The obtained results indicated that the bioprotective effect of non-Saccharomyces yeasts inoculation was determined by the success of the implantation. Only in 2019 assays the inoculum was successfully implanted, and therefore, the bioprotective effect was like the observed for sulphited samples, since it limited the lactic and acetic bacteria population. This inoculation also modulated the physicochemical composition of the resulting wines. However, in 2018 the inoculum was not implanted and differences were not detected, neither in wines composition nor in the detected bacteria.