ANTIOXIDANT CAPACITY OF INACTIVATED NON-SACCHAROMYCES YEASTS

Abstract

The importance of the non-Saccharomyces yeasts (NSY) in winemaking has been extensively reviewed in the past for their aromatic or bioprotective capacity while, recently their antioxidant/antiradical potential has emerged under winemaking conditions. In the literature the antioxidant potential of NSY was solely explored through their capacity to improve glutathione (GSH) content during alcoholic fermentation [1], while more and more studies pointed out the activity of the non-glutathione soluble fraction released by yeasts [2].

Our study proposed to combine untargeted UHPLC-Q-ToF MS based metabolomic analysis with DPPH antiradical activity [3] to explore the antioxidant capacity of compounds released by inactivated non-Saccharomyces yeast (INSY) in wine like model solution. In our experimental plan, 3 INSY species were compared to one inactivated Saccharomyces cerevisiae yeast (ISY) selected for its high antioxidant capacity [4]. In that way, both the species and the production process were evaluated for their impact on the metabolic fingerprint and the antioxidant capacity. Then, unsupervised analysis has been used to extract ions correlated with the antioxidant capacity of the INSY.

Our results show that, all the INSY can accumulate GSH during the specific production process with yields ranging from +170% to +360% compared to the corresponding classical production process. Among the tested INSYs, one presenting equivalent antioxidant capacity to the control ISY while was 4 times less concentrated in GSH (4.73+/-0.09 mg/g against 20.95+/-0.34 mg/g, respectively). The principal component analysis of the 3511 ions detected by UHPLC-Q-ToF MS clearly grouped INSY by species, independently of the production process. 73 specific ions presenting strong and significant spearman correlation (rho < -0.6, p-value < 0.05) with the DPPH scores, clustered the most antioxidant INSY and the control Saccharomyces in different groups, indicating that the antioxidant capacity of these two products should be driven by different pools of compounds.

These results are very valuable for future research perspectives while they point out that, first, GSH alone is not relevant to explain the antioxidant capacity of INSY soluble fraction and other more reactive compounds must be considered. Second, they support the fact that INSY antioxidant capacity is essentially driven by a specie specific metabolism and opens an avenue for the selection new species with great enological potential.