Low‐Temperature Rehydration of Active Dry Wine Yeasts: Nutrient Effects on Fermentation Performance and Membrane Fluidity

Active dry yeast rehydration is a critical step in winemaking, as suboptimal temperatures can impair membrane recovery and compromise fermentation performance. This study evaluated the effects of rehydration at 20°C on commercial Saccharomyces cerevisiae and Torulaspora delbrueckii strains and assessed the efficacy of two commercial rehydration nutrients on fermentation kinetics and membrane fluidity. Results showed that both nutrients enhanced early fermentation in S. cerevisiae strains, with increased CO2 production after 24 h, whereas T. delbrueckii showed no significant response. Membrane fluidity analysis revealed that yeast cells rehydrated at 20°C exhibited high Laurdan generalized polarization (GP) values, indicating increased lipid order, which significantly decreased after 24 h of fermentation. FERMOPLUS Energy Glu 4.0 was associated with lower initial GP values and reduced variation between postrehydration and postfermentation measurements, suggesting a membrane-stabilizing effect that may help optimize rehydration protocols in commercial winemaking.