Brettanomyces : "No barrel is 100 % steril after cleaning"

Thursday February 28 2013 by Vitisphere

"Are there more Brettanomyces in cellars nowadays than there used to be? I do not know ... One thing is for certain: the more you look for them, the more of them you find! " says Nicolas Richard, in charge of Research and Development at Inter Rhône. "In any case, I get calls from producers about Brettanomyces every day. This problem affects wineries in all areas of production. "

Brettannomyces are the contaminating yeast oenologists fear the most. It resists high pH as well as low, the presence or absence of residual sugar, high or low alcohol degree... "Brettanomyces flourish in wood barrels," says Nicolas Richard. "They nest in staves even more easily when the ageing is long and the wine dense and extracted. Due to their wine-making process, high-end wines are most vulnerable to Brettanomyces contamination.''

DBecause of its porosity, wood holds and releases micro-organisms (yeasts, bacteriae ...) and Inter Rhône has therefore developed a protocol to detect the presence of Brettanomyces in wood barrels. Nicolas Richard uses a coring device to sample up to a centimeter of wood on the bottom lath. He then does a cell culture in a Petri dish, and uses PCR (Polymerase Chain Reaction) and flow cytometry techniques to detect the presence of Brettanomyces.

Thanks to its high degree of repeatability, this protocol could be applied to measure the effectiveness of various methods for cleaning barrels after racking (an obligatory precaution to control microbiological risks). "Clearly some processes work better than others", says Nicolas Richard. "Vapor diffusion and sulphur-wicking are effective. So are ultrasound treatments, but this new technique needs improving." In contrast, the application of pressurized hot water, solutions of sodium or ozonated water were not effective, according to the tests run by Inter Rhône. Another crucial conclusion of this study: "whatever the method used, the barrels are never 100% sterilized after cleaning.'

Nicolas Richard is currently working on the development of a risk index, which would assess the potential of a particular wine for Brettanomyces development. In addition, Inter Rhône has also developed a curative method for volatile phenols produced by Brettanomyces contamination.

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