Ensuring the continued efficacy of Brettanomyces control strategies for avoidance of spoilage
Brettanomyces yeast cause wine spoilage by producing 4-ethylphenol and 4-ethylguiacol which are responsible for ‘phenolic’, ‘leather’, ‘sweaty’ and ‘medicinal’ aromas (collectively known as ‘Brett’ character). Although wine spoilage from this yeast was a major issue in Australian red wines produced during the late 1990s and early 2000s, the risk of ‘Brett’ spoilage is now commonly managed via a multi-faceted strategy developed by the AWRI, enabling winemakers to significantly decrease levels of ‘Brett’ spoilage compounds in finished wines. Yet, Brettanomyces has not been eliminated from Australian wineries, and loss of wine value still occurs. To ensure Australian winemakers’ continued ability to manage Brettanomyces in a cost-effective manner, the control strategy must be future-proofed against market pressures to minimise levels of sulfite in wine, and augmented with rapid detection methods.
Can Brettanomyces become more tolerant of sulfite?
Several Brettanomyces strains that differ in their inherent tolerance to sulfite have been exposed over several months to increasing concentrations of this common wine preservative. In each case, a population of cells has been able to grow at sulfite concentrations greater than the original parent strain, or population, could tolerate. The manner in which these experiments have been conducted in the laboratory is analogous to conditions that might be faced by Brettanomyces populations in barrel, where sulfite concentrations drop over time before periodic increases when wines are topped. Further work is now required to confirm that individual clonal cells from these populations are more sulfite-tolerant, and if they are, how stable the trait is. In addition, genomic sequencing will be applied to gain an insight into the mechanisms that may be responsible for developing sulfite tolerance by Brettanomyces.