Brettanomyces are a genus of yeast found on the surface of grapes and in barrels, where hydroxycinamic acids and vinylphenols can be converted into volatile phenols. The formation of volatile phenols has a significant effect on the bouquet of contaminated wine due to the low sensory threshold of these compounds. Typical negative descriptors associated with “Brett” tainted wine are barnyard, manure, leather, tobacco, or medicinal flavours. Brett yeast proliferate in warm conditions with low sulfur dioxide levels and high pH; thus, growth can occur at different times during the winemaking process. The primary compound examined is 4-ethylphenol due the strong association between its production in wine and of Brettanomyces contamination. An additional sensory compound, 4-ethylguaiacol, is analyzed to estimate the impact of contamination.
Chemical analysis of target compounds is a superior choice when determining Brett contamination in wine. Other methods of detection, such as plating, are less desirable due to long incubation periods and non-representative samples. Chemical quantification allows for the analysis of a uniform sample in a timely manner. HS-SPME GC-MS/MS is the most effective way to isolate volatile phenols while providing optimum sensitivity to detect these compounds at low concentrations.