Statistical Evaluation of 4-ethylphenol and 4-ethylguaiacol Concentrations to Support Sensory Evaluation of "Brett Character" of Wines: A Proposed Threshold

Abstract

nalytical data of 260 sensory evaluated wine samples have been statistically examined. All samples had been classified by at least one taster of the five member jury as having "Brett character". Wines have been finally judged as "Good", having "Other defects" or "Brett character". 4-etylphenol (4-EP) and 4-ethylguaiacol (4-EG) concentrations showed different distributions for the "Brett character" group while the other two groups could not be distinguished from each-other. Threshold concentrations for 4-EP, 4-EG and their sum (4-EP + 4-EG) were calculated to classify wine samples as "non-Brett" and "Brett character". 4-EP concentrations were found to be the most reliable markers, with a 245 µg/l lower and 968 µg/l upper threshold. Below or above this range a sample can reliably be classified as "non-Brett" and "Brett character" respectively, while within this range only sensory evaluation can distinguish the two characteristics. Other tested classical analytical parameters did not show significant differences between these groups except for SO₂ which was found to be lower in the "Brett character" group, stressing the importance of sulpihiting as a tool in the fight against Brettanomyces.