Jonathan Brumley,* Ipek Aktuna, and Charles Edwards
*Washington State University, 1455 NE Brandi Way LL-303, Pullman, WA, 99163 (jonathan.brumley@wsu.edu)

We investigated the application of a low ethanol-producing yeast during co-fermentation with Saccharomyces cerevisiae to lower alcohol concentrations in wine. Specifically, this study investigated the complex relationships between yeast assimilable nitrogen (YAN) and sugar concentrations on Metschnikowia pulcherrima in sequential fermentation. A two × three factorial was designed, with YAN (40 mg N/L or 280 mg N/L) and soluble solids (24, 27, or 30 Brix) as variables, by modification of synthetic grape juice media (SGJM). SGJM was fermented by either S. cerevisiae alone, or by M. pulcherrima and S. cerevisiae, the latter inoculated on day 4. Fermentations inoculated with M. pulcherrima reached similar maximum populations (≈107 CFU/mL), except for those containing 40 mg N/L at 30 Brix, where populations were only 106 CFU/mL. In general, M. pulcherrima exhibited an extended lag phase before log growth in media containing 30 Brix, regardless of initial YAN concentrations. All fermentations with 40 mg N/L progressed slower than fermentations with 280 mg N/L. Low YAN fermentations only reached dryness (completion) at 24 Brix, which occurred six days after high-YAN fermentations at the same sugar level. SGJM fermented with M. pulcherrima and S. cerevisiae had lower glycerol concentrations than single-inoculation fermentations in 27 and 30 Brix treatments. Contrary to previous studies, ethanol concentrations were not affected by the presence of M. pulcherrima, except for the treatment containing 40 mg N/L with 24 Brix, which resulted in 0.7% v/v reduction.

Funding Support: Washington State Grape and Wine Research Program