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60 WINES&VINES June 2018 WINEMAKING PRACTICAL WINERY & VINEYARD O nce Brettanomyces bruxellensis takes hold in a winery, eradication is for- midable, often requiring more than one approach to keep the wine- spoilage yeast at bay. Recent findings by Wash- ington State University show that the interaction between storage temperature and alcohol concentration may be a useful tool to manage Brettanomyces. Brett, as it is commonly called in the wine industry, is a wild yeast associated with the spoilage of red wine. Unlike other yeasts such as Saccharomyces, which converts sugars to alcohol and carbon dioxide, Brett is very dif- ficult to control. Though some wineries prefer the earthy and gamey aromas imparted by small amounts of Brett in red wine and believe it adds complexity and aging ability to young wines, a little can quickly turn into too much. When concentrations exceed sensory thresh- olds, Brett can result in wine with "barnyard" aromas that smell like a wet dog, horse sta- bles, sweaty horse blankets, wet wool or sweaty shoes. Dr. Charles Edwards, a professor at Wash- ington State University in Pullman, focuses his research on problem alcoholic fermentations and spoilage organisms of concern to wine- makers. His most recent study, supported by the Washington state wine industry and the Washington State Wine Commission, investi- gates factors that impact Brett's growth and ability to survive under various conditions. Edwards' research includes taking oak bar- rels apart to learn the depth of penetration and survivability of Brett in oak staves under vari- ous conditions and sanitation treatments such as steam, and examining Brett survivability in the winery waste/pomace. The overall goal of his research is to develop effective Brett control measures for wineries. Edwards' work with graduate student Taylor Oswald was recently published in the American Journal of Enology & Viticulture (68:2 2017). His report, "Interactions between Storage Tem- perature and Ethanol that Affect Growth of Brettanomyces bruxellensis in Merlot Wine," is summarized below. Temperature and ethanol (alcohol) concen- tration are two factors known to affect the growth of B. bruxellensis in synthetic media and wine. Previous research found that the optimum temperature for growth of B. bruxel- lensis was from 77° to 83° F in synthetic media. 4 Growth was found to stop above 95° F. 3 Growth in wine and synthetic media have been observed at temperatures as low as 50° F. Researchers also have found that B. bruxellensis can tolerate ethanol concentrations as high as 15% (v/v), 1 but few studies have looked at the interactions among control methods as a way to limit or manage spoilage by B. bruxellensis. For example, the interactions between sulfur dioxide and dimethyl dicarbonate and sulfur dioxide and temperature can affect yeast viabil- ity. 2,6 Additionally, interactive impacts have been studied at pH of 3.4, 3.7 or 4.0; alcohol at 10%, 12.5% or 15%, and free sulfur dioxide of 0, 30 or 50 mg/L on B. bruxellensis. 5 "Our study looked for a relationship between alcohol concentrations and storage tempera- tures," Edwards says. "We wanted to see if winemakers could use ethanol (alcohol) present in the wine and the temperature of storage to- gether as another barrier to manage Brett." The WSU researchers found that the inter- action between storage temperature and alco- hol concentration is important and can help wineries limit and lower the risk of Brett infec- tions. The combination of storage tempera- tures below 54° F and alcohol concentrations of 14% or more resulted in a decline of Brett populations below the detection limit for up to 100 days. Washington state winemaker Brian Carter of Brian Carter Cellars believes the research findings are useful Brett-management tools. Although he uses temperature to help control Brett in his winery in Woodinville, Wash., this information reinforces his practices. "Alcohol levels, temperature and sulfur dioxide are the three most important defenses to use against Brett," he says. Although many small wineries do not have multiple barrel and storage rooms, Carter says the synergistic interactions between alcohol level and storage temperature can still be ap- plied. "Armed with this information, wine- makers should avoid situations where lower alcohol wines are kept at higher temperatures New Tools to Limit Wine Spoilage Interaction of temperature and ethanol may help control Brettanomyces By Melissa Hansen KEY POINTS Cold storage temperature is critical to prevent Brett spoilage. Alcohol content is a key factor in a wine's susceptiblity to Brett. Different strains of Brett can behave and react differently to control methods. Brian Carter, winemaker and owner of Brian Carter Cellars, says alcohol, sulfur dioxide and cellar temperature are the three best tools against Brett contamination.