Analysis of the Metabolic Behavior of Torulaspora delbrueckii and Saccharomyces cerevisiae in Synthetic Musts at Different pHs: An Investigation into the Impact of Climate Change on Alcoholic Fermentation and Main Oenological Parameters

Climate change significantly affects winemaking, altering the composition of grapes and consequently fermentation conditions and wine characteristics. One of the main effects is an increase in must and wine pH. This study analyzes the metabolic behavior of a Torulaspora delbrueckii strain isolated from grapes and a commercial Saccharomyces cerevisiae in sequential fermentations conducted in synthetic musts with different pH values (3.2 and 3.8), with the objective of evaluating yeast adaptation, fermentation kinetics and oenological parameters and determining the potential of T. delbrueckii as a candidate to mitigate the effects of increased must pH in winemaking. Fermentations were conducted under controlled conditions, with T. delbrueckii inoculated first, followed by S. cerevisiae after five days. Our results indicate that T. delbrueckii in sequential fermentation showed greater adaptation to high pH (3.8) than S. cerevisiae alone, maintaining higher population levels throughout fermentation (S. cerevisiae: between 3.7*10⁷ and 6.9*10⁷ ; T. delbrueckii between 1.1*10⁸ and 1.8*10⁸ ). Sequential fermentations with T. delbrueckii resulted in reduced acetic acid production (0.05 g/L at pH 3.8 and 0.17 g/L at pH 3.2), conferring greater fermentative purity and aromatic complexity. NMR analysis revealed differences in metabolites and relative concentrations such as phenylethyl alcohol, with an increase of 4.56 mg/L in sequential fermentation at pH 3.8, and fumaric acid, with an increase of 10 mg/L in sequential fermentation at pH 3.8 and 3.2, determining a clear differentiation between the four theses, especially with regard to the organic acid profile. Future studies should explore its impact on real grape musts and wine sensory attributes. These results suggest that T. delbrueckii could be a valuable tool in winemaking under climate change conditions, helping to improve fermentation performance, reduce volatile acidity and improve wine stability at high pH levels on the starting must.