Brettanomyces yeast — an overview of recent AWRI investigations and some recommendations for its control

Dekkera/Brettanomyces is a yeast that exists in two forms: Dekkera, the sexual sporulating form, and Brettanomyces, the asexual, non-sporulating form. The spoilage of wine by Dekkera/Brettanomyces yeast is well documented, with terms such as “medicinal” “pharmaceutical”, “barnyard-like”, “horsey”, “horse sweat”, “leathery”, “wet dog” and “Band-aid®” having been used to describe the aroma of affected wines. Whether or not the growth of Dekkera/Brettanomyces yeast in wine and the associated aromas should always be considered as spoilage, has been hotly debated. Nevertheless, Dekkera/ Brettanomyces is an organism with the potential to cause spoilage, and therefore it is desirable to understand the relationships between Dekkera/Brettanomyces growth and wine composition in order to be able to manage or control it. Over the past four years, the Institute’s Industry Services team has received more enquiries from industry regarding Dekkera/Brettanomyces yeast and its potential for wine spoilage, than for any other subject except wine bottle closures (which during this period was also the subject of the team’s research activities). As a result of the interest in this topic a seminar relating to Dekkera/Brettanomyces control has been presented to approximately 1,500 winemakers in a number of forums, particularly Institute Roadshows. Additionally, a workshop entitled Trouble free winemaking – the identification, avoidance and management of common wine instabilities, which contains a strong emphasis on the control of microbiological instabilities including Dekkera/ Brettanomyces, has been presented on 15 occasions since it was first developed in 1999. It has become apparent after discussions with winemakers and after numerous investigations conducted by the Institute’s Industry Services team into Dekkera/ Brettanomyces spoilage, that the problem in Australia is widespread. In addition, it has been observed that some of Australia’s Premium, Super Premium and Icon red wines exhibit flavour derived from Dekkera/Brettanomyces, and that the effectiveness of widely applied spoilage control measures, in some cases, is sporadic and inconsistent. It was therefore considered important that an investigation into the many possible facets of the relationship between Dekkera/Brettanomyces yeast and wine composition, including sensory attributes, be conducted.