The antimicrobial action of chitosan against the wine spoilage yeast Brettanomyces/Dekkera

Yeasts of the genera Dekkera and Brettanomyces are well known to be involved in the production of volatile phenols in wines imparting aroma defects that may affect wine quality. The monitoring and control of these organisms is of major importance for wine producers. This study aimed to evaluate the effect of chitosan, a natural polysaccharide, on the survival of Brettanomyces/Dekkera and on some physicochemical aspects of wine (pH value, colour intensity and hue, anthocyanin content and antioxidant capacity). Minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC) values were determined for 8 strains of Brettanomyces/Dekkera by the broth microdilution technique. The results show that chitosan inhibits the growth of Brettanomyces/Dekkera at concentrations ranging from 0.20 to 0.50 mg/ml, depending on the molecular weight of the chitosan molecules and on the assayed strain. The low molecular weight (LMW) chitosan presented the smaller MIC values. Time-kill assays performed in wine added of LMW chitosan revealed reduction of yeast cell viability over time. Furthermore, chitosan affected some physicochemical characteristics of wine, particularly the hue and colour intensity. Relevant data, potentially useful for the establishment of regimes comprising the use of chitosan for the control of Dekkera/Brettanomyces yeasts in wine, is presented.