Taylor A. Oswald and Charles Edwards* 
*Washington State University, School of Food Science, Pullman, WA 99164 (edwardsc@wsu.edu)

The potential for synergy between temperature and ethanol as a means to control infections by Brettanomyces bruxellensis in red wines was examined. Using a commercially-prepared Merlot wine, a four × five factorial experimental design was employed with storage temperature (12, 15, 18, or 21°C) and ethanol (12, 13, 14, 15, or 16% v/v) as variables. Culturabilities of two strains of B. bruxellensis isolated from Washington wines (I1a and F3) were monitored for 100 days before concentrations of volatile acidity, 4-ethylphenol (4-EP), and 4-ethylguaiacol (4-EG) were quantified. While growth of both strains was observed in 12 to 15% v/v ethanol, lag phase duration generally increased with a decrease in temperature. The two strains demonstrated similar growth patterns under various temperature × ethanol conditions except in those wines containing 15% v/v ethanol. At this concentration, F3 exhibited less growth and reduced concentrations of volatile acidity, 4-EP, or 4-EG at higher temperatures (18 and 21°C) than I1a. Strain F3 grew better at 18°C than at 21°C at this concentration of ethanol. Culturabilities of both strains quickly declined in wines containing 16% v/v ethanol. Wines in which B. bruxellensis reached >106 cfu/mL frequently contained concentrations of 4-EP and 4-EG in excess of 1290 and 155 µg/L, respectively, and above olfactory thresholds. Given significant interactions between temperature and ethanol, wines containing below 13% v/v ethanol should be stored at ≤12°C to help limit spoil-age by this yeast.

Funding Support: Washington Wine Advisory Committee, Lallemand (Montréal, Quebec, Canada), and School of Food Science (Washington State University, Pullman)