Glossary
Phenol
Yeast-derived compounds giving clove, pepper, smoke and — at the wrong end — medicinal or plastic character.
Also called phenolic, phenols, 4-vinyl guaiacol, pof.
The clove note in a Hefeweizen and the peppery spice of a saison are 4-vinyl guaiacol and its relatives, produced by yeast strains carrying the POF gene. Most clean ale and lager strains do not carry it, which is why phenolic character is a strain choice rather than an accident.
The medicinal, TCP or plastic version is a different matter: chlorophenols, formed when chlorine or chloramine in brewing water reacts with phenolic compounds. That one is always a fault, and it is preventable by treating the water.
Commonly misunderstood
"Phenolic" is used both as praise and as a fault report. The clove-and-pepper kind is stylistic; the TCP-and-plastic kind is a water treatment failure.
Related
- Ester — The other yeast-derived flavour class.
- Chlorophenol — The version that is always a defect.
- Weissbier — The style defined by the desirable form.
More vocabulary
Astringency · Body · Chill haze · Ester · Head retention · Hop burn · Lacing · Mouthfeel
See every term on the glossary index.
Last reviewed 2026-08-16.
Evidence
What BeerHQ knows about this, and how. Every statement carries the state of the evidence behind it rather than being presented flatly as fact.
Not every phenolic character in beer comes from brewing yeast: Brettanomyces produces the volatile phenols 4-ethylguaiacol and 4-ethylphenol, which read as bandage, sweat and smoke rather than as the clove of a Weissbier.
Checked against the source
Source: Bokulich & Bamforth, "The Microbiology of Malting and Brewing" (2013), Yeasts (beer-spoilage organisms) (Microbiol Mol Biol Rev 77(2):157–172)