Cold plasma at atmospheric pressure for eliminating Brettanomyces from oak wood

Abstract

In the oenological industry, the maintenance and sanitation of oak barrels has become a fundamental task. The wood has a porous structure that facilitates the penetration not only of the wine, but of the microorganisms it contains, such as the alterative yeast Brettanomyces bruxellensis. Although the most widely used method of sanitizing barrels is the burning of sulfur tablets, there is a European directive that will limit this practice, even when an effective alternative has not yet been found. This research is part of a project that studies the application of cold plasma at atmospheric pressure (APCP) to sanitize oak wood staves. This alternative technology to sulfur is respectful with the environment. In this study, various fragments of staves artificially contaminated with Brettanomyces bruxellensis were exposed to the APCP device with different plasma gas and distinct plasma strengths. The results showed inactivations of 2.89 logarithmic units (of colony-forming units per milliliter) using argon for plasma generation. Absolute inactivations (5.46 log units) were reached when air or nitrogen was used for plasma generation. Nor any morphological modifications were seen on the surface of the wood after the APCP treatments. Despite the promise of these results, this line of research should be continued to solve the difficulties that may arise when treating naturally contaminated wood fragments in the wineries, as well as when facing their industrial scale.