The invention relates to a chitosan in the form of a micronised powder, to the use thereof to combat certain yeasts, such as Brettanomyces, and to a method for the treatment of a liquid food. In particular, the invention relates to a water-insoluble chitosan in the form of a micronised powder having a grain size of between 5 and 50 micrometres and to the use thereof in the treatment of liquid foods and/or to combat Brettanomyces.
