4-Ethylphenol

A white solid, it occurs as an impurity in xylenols and as such is used in the production of some commercial phenolic resins.

At concentrations greater than 140 μg/L (typical sensory threshold) it gives the wine aromas described as barnyard, medicinal, band-aids, and mousy.

The level of 4-EP is roughly proportional to Brettanomyces concentration and activity, and can therefore be used as an indicator of the yeast's presence.

There are significant differences between strains of Brettanomyces in their ability to produce 4-EP.

Coumaric acid is sometimes added to microbiological media, enabling the positive identification of Brettanomyces by smell.

NFPA 704 four-colored diamond Health 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroform Flammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oil Instability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogen Special hazards (white): no code
The conversion of p -coumaric acid to 4-EP by Brettanomyces