Enumeration and Identification of 4-Ethylphenol Producing Yeasts Recovered from the Wood of Wine Ageing Barriques after Different Sanitation Treatments

Aims: This work was aimed at the evaluation of several sanitation procedures on the reduction of total microbial flora and of D. bruxellensis recovered from the inner layers of the barrique’s wood. Methods: A group of used oak barrels tainted by 4-ethylphenol and contaminated with D. bruxellensis were differently sanitized and, afterwards, were dismantled to analyse samples of shaves taken from wood surfaces at different depths. Microbial counts were obtained by the Most Probable Number Technique using broths of general purpose medium and of Dekkera/Brettanomyces differential medium (DBDM). Results: The least inefficient treatment included barrique steaming at low pressure. Uncontaminated samples were only detected under this treatment and in the upper level (0-2 mm) of the staves. With this treatment complete destruction of the contaminating flora was not achieved in any level of stave side surfaces and in grooves. The presence of D. bruxellensis was detected in depths up to 6-8 mm in the wood corresponding to the maximum level of wine penetration. Significance: this work demonstrated that even after current sanitation procedures barriques used in wine maturation pose a severe risk to wine stability due to the presence of D. bruxellensis.