Effectiveness of Ozone against Different Strains of Brettanomyces bruxellensis on Postharvested Winegrapes and Impact on Wine Composition

Spoilage by Brettanomyces bruxellensis is a major concern for the wine industry. The negative effect of this yeast on wine quality, due to the production of phenolic off-flavors, and potentially large associated economical losses, requires the application of specific control measures. In this study we investigated the ability of ozone to control B. bruxellensis population on Barbera treated wine grapes berries and the impact on subsequent winemaking or fermentation. To further explore the ability of the ozone treatments to reduce B. bruxellensis population, a mix of three different strains were artificially inoculated on the surface of grape berries. Grape berries were ozone-treated either in aqueous (6 and 12 min) or gaseous form (12 and 24 h), crushed and then fermented to evaluate the effect of these treatments on B. bruxellensis and S. cerevisiae growth dynamics and wine composition. Microbiological analysis revealed a significant reduction of B. bruxellensis of about 2.2 Log colony forming units (CFU)/mL after treatments with gaseous ozone for 24 h. The wines produced from grape berries previously exposed to gaseous ozone for 24 h contained the lowest levels of acetic acid. Moreover, 4-ethylphenols were detected in wines produced from grape berries treated with water (6 and 12 min), in which B. bruxellensis population reached 5.0 Log CFU/mL at the end of fermentation. Molecular analysis results suggest that the three different strains tested had similar sensitivity to the ozone treatments applied. This study shows the first results about the ability of ozone to control the population of different B. bruxellensis strains within the same species in the same manner.