Preliminary lab scale of advanced techniques as new tools to reduce ethylphenols content in synthetic wine
Effects of low electric current (LEC) and/or activity of laccase from Trametes versicolor on 4-ethylguaiacol and 4-ethylphenol and their phenolic precursors (ferulic and p-coumaric acids) were investigated by working in small volumes of synthetic wine and with multiple tests. Above ethylphenols are produced by Brettanomyces/Dekkera sp. yeast and are associated with a serious taste defect in wine, known as ‘brett character’. Both techniques have produced a significant reduction of all phenolic compounds. Specifically, concentration of 4-ethylguaiacol and 4-ethylphenol was approximately 32 percent reduced as result of application of electric current (200 mA for 20 min). In comparison, after an incubation at environmental temperature for 20 min, laccase has produced a reduction of 4-ethylguaiacol and 4-ethylphenol by 55.3 and 44.1 percent, respectively. Finally, by applying together both two techniques (LEC and laccase) ethylphenols and their precursors were almost degraded completely.
Presence of a large amount of ethylphenols in wine is normally considered a negative factor since these compounds are associated to characteristic off-flavour that is evaluated as barn, horse sweat, clove or leather, mice urine (1). Yeasts of the genus Brettanomyces/Dekkera mostly produce ethylphenols, especially 4-ethylguaiacol and 4-ethylphenol, through decarboxylation and subsequent reduction of their precursors, which as the ferulic and p-coumaric acids, respectively (2). As result, a typical flavour defect, named ‘brett character’, is generated in the wine (3).
Brettanomyces/Dekkera strains are largely ubiquitous in the wineries where in colonize areas difficult to wash and sanitize, such as pumps, pipes, valves and wooden barrels. Brettanomyces/Dekkera growth is strongly favoured by presence of oxygen, high temperatures, high pH and low levels of molecular SO2 (4). Furthermore, Brettanomyces/Dekkera strains are low sensitive to ethanol and grow also with a small amount of residual sugar (5). Consequently, brett character can also occur when wine is stored in bottles or barrels, causing relevant economic damage.