The aroma of Band-Aids in wine is a good indicator of so-caLLed 'Brett character'. In some cases, the aroma may be even more medicinal, or in extreme cases, horse dung is a common descriptor. The aroma is related to the presence of 4-ethylphenol (4-EP), which may be coupled with that of cloves, bacon or wood smoke arising from 4-ethylguaiacol (4-EG). On the palate, the tannins in red wine may seem gritty or metallic, lacking the smoothness that one seeks in a great red wine. The sensory threshold is wine dependent with the value for 4-EP being between 300 and 600 pg/L, considerably higher than that for 4-EG (around 10 pg/L). The production of these off-odours results from the actively metabolising yeast Dekkera/Brettanomyces bruxettenis (Brett) converting hydroxycinnamic acids (C6-C3 phenoLic acids) to ethyl phenol compounds. More detail can be found in the article by Lorenza Contemo and colleagues in Food Research International (2013, vol. 51, pp. 670-8).
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