<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 10⁶ 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 10⁵ cfu/mL down to ≈10² 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>

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New 16 L and three-year-old commercial 225 L barrels representing French and American oaks of different toasting levels, contaminated with Brettanomyces bruxellensis, were obtained. Center sections of individual staves were sawn into 3 x 3 cm cubes and submerged 2 mm into heated water at 50°C, 60°C, 70°C, or 80°C. Following heat treatment, cross sections and/or shavings were collected and transferred into a yeast recovery medium for incubation for ≥60 days. Culturable cells were not recovered from cubes heated in water at 70°C for 20 minutes, or 80°C for 15 minutes, when the yeast was present in oak at depths of ≤4 mm. However, longer heating times (70°C for 30 min or 80°C for 20 min) were required if B. bruxellensis was present at depths of 5 to 9 mm within cubes made from staves. Based on these results, heating water to at least 70°C for a minimum of 30 minutes is recommended to reduce risk of wine spoilage by barrels contaminated with B. bruxellensis.

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