New oak barrels may be responsible for brettanomyces, consultant winemaker Matt Thomson has said.
Thomson, who consults for New Zealand's Saint Clair winery as well as Italian and French producers, was speaking about the yeast infection that can strip a wine of its fruit and create aromas described as 'mousey' or 'horsey', at a seminar on brettanomyces hosted by Liberty Wines.
He said, 'Although some scientists don't agree, many winemakers – myself included – believe that the source of brettanomyces lies in new barrels coming into a winery.'
Once a winery is infected by the rogue yeast, it can be extremely difficult to get rid of as the risk of cross-contamination is high and preventative measures can limit the range of vinification techniques used by winemakers.
Thomson believes that the incidence of brettanomyces has increased in recent years. 'I think it's a relatively new thing in many Old and New World regions,' he said, adding that he thinks the increase is, 'partly down to new wine styles that are low in acidity and relatively high in residual sugar, but also due to increased demand for new oak barrels.'
He speculated that this increased demand for new oak may have led to the harvesting of wood from infected sources – and that the toasting process involved in creating new barrels may produce compounds that may be a source of food for the Brettanomyces cells.
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There appears to be a heightened paranoia for brett in NZ and Australia and this is yet another chapter of misinformation. If the brett yeast cells were indeed present in the barrel it would be simple to test the supposition by rinsing the barrel and then plating the water. If the brettanomyces exists in the oak then it would have infested the entire cooperage producing the barrels, but what would it feed off of? Furthermore, there would be a cross the board epidemic of brett with all the cooperages.
I believe the correct conclusion is this: the new barrels have polysaccharides that can be ingested and feed the brett(which is already in the wine and the winery), older barrels are typically left empty and sulpher gassed making it a less habitable environment for the brett where as new barrels should have no sulpher in them. The combination of higher pH, completing ML in barrel, residual sugar, and a cross swapping of used cooperage between wineries seems like a more likely candidate. Perhaps a proper sanitization of the used barrels and the winery, along with proper temperature control in the barrel room, and higher free sulpher levels would be a better approach to the problem.
As a side note; I have tasted many wines in my tasting groups and upon further analysis of the favored wines, the 4 EP/ 4 EG levels were all above threshold for analysis and yet the wines supported the component which other weaker wines would not have.
Bayard Fox, Saury USA
I presented research on Brettanomyces, conducted during production-scale barrel-aging of Cabernet Sauvignon at Robert Mondavi Winery, some years ago at Intervitis in Germany. I would like to obtain more detailed information on Mr. Thomson's supposition.
I was confused by the following part of the November 21 article by Natasha Hughes: “He speculated that this increased demand for new oak may have led to the harvesting of wood from infected sources – and that the toasting process involved in creating new barrels may produce compounds that may be a source of food for the Brettanomyces cells”. I don't think the intended meaning of “…..wood from infected sources…..” means that Brettanomyces infections are potentially originating from the forest, but that is the implication from that sentence.
Thanks in advance for your assistance.
Patrick Mahaney, Premier Pacific Vineyards, Napa, CA, USA
This report is based on pure speculation. According to the article, Matt Thompson did not site any research or winery trials that would substantiate his belief. Both Thompson and the Editor should consider the wide-ranging implications before publishing such an irresponsible and unprofessional article.
Tom Rees, Assistant Winemaker, St. Supery Vineyards and Winery
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There appears to be a heightened paranoia for brett in NZ and Australia and this is yet another chapter of misinformation. If the brett yeast cells were indeed present in the barrel it would be simple to test the supposition by rinsing the barrel and then plating the water. If the brettanomyces exists in the oak then it would have infested the entire cooperage producing the barrels, but what would it feed off of? Furthermore, there would be a cross the board epidemic of brett with all the cooperages.
