Brettanomyces spoilage is still a critical issue in the wine industry today . Despite its status as a spoilage yeast, the presence of Brettanomyces is required in fermentation of certain specialty beers such as Berliner Weisse, lambic, and sour English beers to obtain their characteristic complex "Brett" flavour . In wine, the "Brett" character is associated with negative descriptors such as mousey and metallic but also with positive descriptors such as fruity, tropical and floral . 4-EP and 4-EG are the major metabolites responsible for "Brett" character, but several volatile ethyl esters including ethyl acetate, ethyl lactate, ethyl caprate and ethyl caprylate contribute to the fruity and floral descriptors . The difference in perception of "Brett" character between beer and wine is heavily influenced by the relative concentrations of 4-EG and 4-EP, where 4-EG is higher in beer and 4-EP is higher in wine .