Estimation of Brett Odour in Wine

Projects

Author

Sierra Rayne and Nigel Eggers

Initiation date

2006-08-01

Completed

Synopsis

Introduction to 4-Ethylphenol, 4-Ethylguaiacol, and the Brettanomyces/Dekkera Connection

Brett is probably resident in most Okanagan wineries, but is kept in check by current sterile techniques, and the 4-ethylguaiacol and 4-ethylphenol concentrations are very likely well below their thresholds. The concentrations of these two compounds can be used to monitor the effectiveness of Brettanomyces control programs. This analytical method for estimating the extent of Brettanomyces contamination is rapid and will quickly provide information regarding the effectiveness of the sterile techniques.

The study of Brettanomyces infection will take into account many variables and will include the following: age of barrel, cooper, block of grapes, variety of grapes, hygiene (hot versus cold water, sterilizing agent), type of oak used in barrels, sulphur dioxide concentration, cellar temperature, and dissolved oxygen.

Key Findings

Brettanomyces (“Brett”) is a wild yeast implicated in the spoilage of red wine and has long been associated almost exclusively with European wines, but in recent years is considered to occur in wines from the New World
Two compounds that are widely considered to be primarily responsible for the ‘Brett’ odour are 4-ethylphenol and 4-ethylguaiacol:
Brettanomyces (the asexual, nonsporulating form) and Dekkera (its sexual, sporulating form) are ubiquitous in the vineyard and winery, and are likely to be present in the water, the soil, the grapes and must, and throughout the winery – and their presence can be monitored, but not controlled (Arvik and Henick-Kling, 2002)
Once this yeast is established in a winery, it is difficult to eliminate → spoilage of wine by Brettanomyces can be devastating and
wineries have had to shut down to remove this contaminant
Maintaining appropriate sulfur dioxide (SO2) levels, lower temperatures (generally <20°C), filtration, excluding oxygen ingress into the wine during topping up of barrels (and keeping the barrels topped up), and general winery hygiene have all been noted as methods to keep “Brett” problems minimized (Arvik and Henick-Kling, 2002)
However, infected barrels cannot effectively be sterilized due to their large internal surface areas and porosity, whether it be by washing with sulfited water, shaving and firing, or ozone treatment (Arvik and Henick-Kling, 2002 and their citation of Kunkee, 2001; Pollnitz et al., 2000a), with Brettanomyces found as deep as 8 mm into the oak wood (Malfeito-Ferreira et al., 2004)
For these reasons, we recently (in May 2006) began a comprehensive two-year study based in the Okanagan Valley wine region of British Columbia, Canada, that is targeted at better understanding the levels, distributions, fate, and factors governing the production of the two most well-known Brettanomyces metabolites: 4-ethylphenol and 4-ethylguaiacol

Project Updates

Brett_Odour_Project_Results_Summary_Aug-2006_0

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