Minimization of ethylphenol precursors in red wines via the formation of pyranoanthocyanins by selected yeasts

Different strains of Saccharomyces with different hydroxycinnamate decarboxylase (HCDC) activities, estimated by a bioconversion assay, were used for the fermentation of musts enriched with p-coumaric acid and grape anthocyanins, with the aim of favouring the formation of vinylphenolic pyranoanthocyanins, colour stabilization and (especially) the minimization of 4-ethylphenol. The development of anthocyanin-3-O-glucosides (precursors of vinylphenolic adducts), the decarboxylation of p-coumaric acid, and the formation of 4-vinylphenol, 4-ethylphenol and vinylphenolic pyranoanthocyanins were monitored by HPLC-DAD-ESI/MS. After fermentation, the wines were inoculated with large numbers (104 CFU/ml) of Dekkera bruxellensis to establish their potential for ethylphenol production. The HCDC activity of the strains significantly increased the formation of vinylphenolic pyranoanthocyanins and reduced the final concentration of 4-ethylphenol and 4-ethylguaiacol generated by the vinylreductase activity (VPhR) of D. bruxellensis. Early decarboxylation of hydroxycinnamates to vinylphenols, by means of Saccharomyces strains with strong HCDC activity, and their subsequent binding with anthocyanins to form stable pyranoanthocyanins, is a possible way to reduce the likelihood of ethylphenol production by Brettanomyces during in-barrel aging.