Abstract
<p style="text-align: justify;"><strong>Aim</strong>: The antimicrobial properties of chitosan from different sources (fungal, crab shell, and lactate-forms) against <em>Brettanomyces bruxellensis</em> in culture media and red wines were investigated.</p><p style="text-align: justify;"><strong>Methods and results</strong>: While concentrations of 4 to 8 g/hL were needed for crab shell or lactate-forms of chitosan to reduce yeast viability in liquid media, fungal chitosan did not exhibit antimicrobial activities no matter the concentration. <em>B. bruxellensis</em> E1 and I1a were inoculated into Cabernet Sauvignon wine at 10<sup>6</sup> cfu/mL and treated with 0, 4, 8 and 12 g/hL fungal chitosan. In contrast to previous results with media, addition of fungal chitosan to a red wine resulted in a three-log reduction of culturability. Addition of fungal chitosan also reduced the viability of <em>B. bruxellensis</em> growing in oak barrels containing Merlot wine from 10<sup>5</sup> cfu/mL down to ≈10<sup>2</sup> cfu/mL.</p><p style="text-align: justify;"><strong>Conclusion</strong>: Depending on concentration, all preparations of chitosan added to red wines greatly reduced populations of <em>B. bruxellensis</em>. However, wines were not completely stable after treatment as populations eventually increased.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: As <em>B. bruxellensis</em> is considered to be a worldwide threat to wine quality, it is crucial to improve knowledge of alternative control methods and strategies such as chitosan that winemakers can apply.</p>
Highlights
Limiting or eliminating the spoilage yeast, Brettanomyces (Dekkera) bruxellensis, from red wines is not an easy task for winemakers
Depending on concentration, all preparations of chitosan added to red wines greatly reduced populations of B. bruxellensis
Significance and impact of the study: As B. bruxellensis is considered to be a worldwide threat to wine quality, it is crucial to improve knowledge of alternative control methods and strategies such as chitosan that winemakers can apply
Summary
Limiting or eliminating the spoilage yeast, Brettanomyces (Dekkera) bruxellensis, from red wines is not an easy task for winemakers. Sulfites are known to cause human allergic reactions (Vally and Thompson, 2001), thereby necessitating the need to develop alternative strategies One such approach could be the use of chitosan, a compound that has antimicrobial properties against a variety of bacteria and yeast species (Roller and Covill, 1999; Martín-Diana et al, 2009). Gómez-Rivas et al (2004) studied antimicrobial action of chitosan from crab shells against Saccharomyces cerevisiae and B. intermedius (B. bruxellensis). These authors observed addition of very high concentrations of chitosan (300 to 600 g/hL) resulted in inhibition of B. bruxellensis in a culture medium while S. cerevisiae was unaffected. Recent work by Taillandier et al (2015) concluded that the antimicrobial action against B. bruxellensis was the result of a number of mechanisms including cell aggregation and leakage of certain constituents
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