Interactions between Storage Temperature and Ethanol that Affect Growth of Brettanomyces bruxellensis in Merlot Wine

The potential for synergy between temperature and ethanol as a means to control infections by Brettanomyces bruxellensis in red wines was studied. Using a commercially prepared Merlot wine, we employed a 4 x 5 factorial experimental design with storage temperature (12, 15, 18, or 21 degrees C) and ethanol (12, 13, 14, 15, or 16% [v/v]) as variables. Culturabilities of two B. bruxellensis strains (I1a and F3) 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 displayed similar growth patterns under the various temperature x ethanol conditions, except in the wines containing 15% (v/v) ethanol. At this concentration, F3 exhibited less growth and reduced concentrations of volatile acidity, 4-EP, and 4-EG at the higher temperatures (18 and 21 degrees C) than did I1a. In fact, F3 grew better at 18 degrees C than at 21 degrees C at 15% ethanol. Culturabilities of both strains quickly declined in wines containing 16% v/v ethanol. Wines in which B. bruxellensis reached > 10(6) cfu/mL frequently contained concentrations of 4-EP and 4-EG in excess of 1290 and 155 mu g/L, respectively, and thus above the olfactory thresholds for the two compounds. Given the significant interactions between temperature and ethanol, wines containing > 13% (v/v) ethanol should be stored at <= 12 degrees C to help limit spoilage by this yeast.