How does the inoculation mode of selected oenological yeasts influence wine profiles?

Abstract

Yeasts profoundly influence winemaking outcomes, not only by driving alcoholic fermentation but also by shaping the chemical and aromatic diversity of wines. Beyond the standard rehydration of Active Dry Yeasts (ADY), alternative preparation methods such as pre culturing—akin to a pied de cuve—have regained interest, as they involve a phase of yeast multiplication prior to must inoculation and are known to modify fermentation dynamics. In this work, we investigated how these two inoculation strategies affect the metabolism of three commercial Saccharomyces cerevisiae strains and the resulting composition of Chardonnay wines by combining high resolution, targeted and untargeted metabolomics. Although classical oenological parameters remained unchanged between inoculation modes, deep metabolic profiling revealed marked differences in both the volatilome and exometabolome. HRMS analysis showed that yeast preparation prior to inoculation profoundly affects metabolic activity, with over a thousand biomarkers modulated depending on the method used. Wines fermented from rehydrated ADY displayed signatures enriched in polyphenol related compounds and higher levels of esters, whereas pre cultured yeasts produced wines characterized by metabolites associated mainly with nitrogen metabolism. Interestingly, the metabolic fingerprints of wines produced with multiplied yeast converged across strains, while those from directly rehydrated ADY retained strain specific profiles. Altogether, these results demonstrate that the physiological state imposed by the inoculation method leads to a substantial reprogramming of yeast metabolism, determining both the non volatile and volatile chemical compositions of the finished wines.