Issues related to Brettanomyces in the winemaking sector are purely organoleptic. These yeasts are able to grow in wines during ageing (Froudière and Larue, 1988) or in bottled wines, and can produce unpleasant flavour compounds by breaking down phenolic acids. These compounds include 4-ethylphenol and 4-ethylguaiacol (Chatonnet et al. 1995).