|Schopp, Lauren - WASHINGTON STATE UNIVERSITY|
|Osborne, James - OREGON STATE UNIVERSITY|
|Chescheir, Stuart - OREGON STATE UNIVERSITY|
|Edwards, Charles - WASHINGTON STATE UNIVERSITY|
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/13/2013
Publication Date: 11/27/2013
Publication URL: http://dx.doi.org/10.1021/jf403440k
Citation: Schopp, L.M., Lee, J., Osborne, J.P., Chescheir, S.C., Edwards, C.G. 2013. Metabolism of nonesterified and esterified hydroxycinnamic acids in red wines by Brettanomyces bruxellensis. Journal of Agricultural and Food Chemistry. 61:11610–11617.
Interpretive Summary: Strains of the spoilage yeast Brettanomyces bruxellensis were evaluated for their ability to convert the natural phenolic acid components found in grape juice/must into undesirable aromas (often described as barnyard or band-aid smells). Washington and Oregon red wines were inoculated with different strains isolated from wine samples collected in commercial wineries of Washington and California. Strains varied in their ability to convert phenolic acid precursors into corresponding undesirable aroma compounds. The strains evaluated in this study appeared to lack the necessary enzymes that breakdown the prevalent grape phenolic acids (esterified hydroxycinnamic acids like caftaric and coutaric acids) into simpler phenolic acids (non-esterified hydroxycinnamic acid like caffeic and coumaric acids) that allow for conversion into unwanted aromas.
Technical Abstract: While Brettanomyces can metabolize non–esterified hydroxycinnamic acids found in grape musts/wines (caffeic, p–coumaric, and ferulic acids), it was not known whether this yeast could utilize the corresponding tartaric acid esters (caftaric, p–coutaric, and fertaric acids, respectively). Red wines from Washington and Oregon were inoculated with B. bruxellensis while hydroxycinnamic acids were monitored by HPLC. Besides consuming p–coumaric and ferulic acids, strains I1a, B1b, and E1 isolated from Washington wines metabolized 40 to 50% of caffeic acid, a finding in contrast to strains obtained from California wines. Higher molar recoveries of 4–ethylphenol and 4–ethylguaiacol synthesized from p–coumaric and ferulic acids, respectively, were observed in Washington Cabernet Sauvignon and Syrah but not Merlot. This finding suggested that Brettanomyces either (a) utilized vinylphenols formed during processing of some wines or (b) metabolized other unidentified phenolic precursors. None of the strains of Brettanomyces studied metabolized caftaric or p–coutaric acids present in wines from Washington or Oregon.