In wine and beer, 4-EP is produced by the yeast Brettanomyces. At concentrations greater than 140 μg/L (typical sensory threshold) it gives the wine aromas described as barnyard, medicinal, band-aids, and mousy.
The yeast Brettanomyces produces 4-EP in wine and beer. At levels above 140 µg/L, this compound creates flavors that are often perceived as barnyard, medicinal, band-aid, or mousy.