Studies on the incidence of Dekkera bruxellensis in Turkish wines and effect of low temperatures on 4-ethylphenol production

Mestrado Vinifera EuroMaster - Instituto Superior de Agronomia ; Brettanomyces/Dekkera bruxellensis has the ability to produce significant amounts of 4-ethylphenol (4-EP) and cause important organoleptic defects in affected wines. In this work we investigated the incidence of B. bruxellensis and of 4-ethylphenol in Turkish red wines randomly collected at winery facilities. Among 40 samples, this species was only recovered from one sample aged in oak barrels. In 4 samples, culturable population was not found but the 4-EP concentration indicated previous Dekkera bruxellensis activity. Thus, following potential Brettanomyces-sourced aroma impacts in wine using 4-Ethylphenol and 4-Ethylguaiacol concentrations as proxies should only be considered reliable at analyte levels >100 μg/l (Rayne and Eggers, 2007). Furthermore, we studied the influence of storage temperature on the production of 4-EP by wild of D. bruxellensis in 3 different Portuguese red wines. Temperatures of 10 ºC and 15ºC were not effective in preventive the increase of 4-EP over 600 μg/l during 90 days. At 3 ºC one sample showed similar 4-EP increase while in two other samples its concentration was kept unchanged. Production of 4-EP at 3ºC and 10ºC was confirmed when the strain TR 26 was incubated in red wine for 49 days. However, the total amount of 4-EP produced was below 150 μg/l while at 15ºC and 20ºC the values reached 1600 μg/l. Therefore, the effect of low temperatures acts by delaying microbial growth which results in lower concentrations of 4-EP but once temperature increases 4-EP production is readily stimulated