A simple, cheap and reliable method for control of 4-ethylphenol and 4-ethylguaiacol in red wines. Screening of fining agents for reducing volatile phenols levels in red wines.

Abstract

Brettanomyces/Dekkera produces 4-ethylphenol (4-EP) and 4-ethylguaiacol (4-EG) from hydroxycinnamic acids that affect the wine aroma and overall quality. A simple, cheap, fast and reliable quantitation method is needed for routine quality control of wines. In this work a simple method based on one simple liquid-liquid extraction with pentane/diethyl ether (2:1) and analysis by GC-MS allow to obtain very good recoveries (98-102%) and low quantification limits (24 and 11μg/L for 4-EP and 4-EG, respectively), well below the sensory threshold for these volatile phenols and with an adequate measurement uncertainty: 70, 1.75 and 78, 1.95 and 1.35μg/L for levels of 1000, 25μg/L for 4-EP and 1000, 25 and 10μg/L for 4-EG, respectively. In addition a screening of eight fining agents (mineral, protein and polysaccharide based) for reducing the levels of these volatile phenols in red wines was performed, and the impact on the physicochemical characteristics of red wines was evaluated. At the levels used, activated carbon was the most efficient fining agent in removing 4-ethylphenol and 4-ethylguaiacol from red wines (57%) resulting in a 75% decrease of headspace concentration of these volatile phenols. Lower reductions were observed when using egg albumin (19%) resulting in a 30% decrease in the headspace concentration. Other fining agents although not reducing the total amount of the volatile phenols present in wine decreased their concentrations in the headspace like isinglass (27%), carboxymethylcellulose (15%) and chitosan (27%). All of these fining agents could be a possibility for treating wine contaminated with 4-ethylphenol and 4-ethylguaiacol.