The Influence of Brettanomyces/Dekkera sp. Yeasts and Lactic Acid Bacteria on the Ethylphenol Content of Red Wines

Abstract

The ability of various lactic acid bacteria isolated from wine to synthesize volatile phenols from trans p-coumaric and ferulic acid was studied in a model medium and compared with that of Saccharomyces cerevisiae and Dekkera intermedia. Quantitative analysis of the produced vinylphenols and ethylphenols showed that some strains of Lactobacillus brevis and Pediococcus pentosaceus were capable of decarboxylating p-coumaric acid to form 4-vinylphenol as actively as S. cerevisiae, whereas the same bacteria had a much less marked effect on ferulic acid. The other bacteria, Leuconostoc oenos in particular, only synthesize very small quantities of vinylphenols. Apart from Lactobacillus plantarum, none of the other lactic acid bacteria studied released any significant quantities of ethylphenols during culture. However, the quantities of ethylphenols produced by L. plantarum were still very small compared to those formed by D. intermedia and have no negative impact whatsoever on the wine's aroma. The influence of lactic acid bacteria on the volatile phenol content of wine is, therefore, very restricted. These findings confirm that Brettanomyces/Dekkera are responsible for the development of a phenolic character in red wines. These yeasts multiply by fermenting the small quantities of residual sugars (glucose, fructose, galactose, and trehalose) in the wine. The fermentation of barely 275 mg/ L of sugars, much less than the normal residual sugar level of new red wine at the end of the usual fermentation process, is sufficient to synthesize an excessive quantity of ethylphenols with alteration of the aromatic quality of the wine.