Phenols represent a broad class of compounds that may be very welcome or completely undesirable in beer, depending on the brewer’s intention and the target style. Chemically speaking, a phenolic compound contains hydroxyl (OH) and a ring of hydrogen and carbon molecules (an aromatic hydrocarbon ring). Such compounds are prolific in nature and are responsible for many well-known flavors and aromas:
- Capsaicin gives chiles their fiery bite.
- Carvacrol is responsible for oregano’s pungency.
- Eugenol is found in cloves, nutmeg, cinnamon, and vanilla.
- Guaiacol is the smoky essence in whiskey and roasted coffee.
- Methyl salicylate smells and tastes just like wintergreen.
- Raspberry ketone smells like raspberries.
- Thymol is what gives thyme its distinctive aroma.
Phenolic compounds are also produced synthetically for industrial and pharmaceutical applications. But when it comes to beer, you may or may not want phenolic character. As usual, it really depends on what you’re after:
- Bavarian Weißbier, or Hefeweizen derives its signature clove character from 4-vinyl guaiacol.
- Saison often contains a mix of clove and pepper-like phenols.
- Brettanomyces-driven styles are often described as horsey or barnyard-like thanks to 4-ethyl phenol.
While cloves, pepper, and even sweaty horse blankets may be desirable in certain brews, other phenolic flavors are rarely welcome guests. If your beer tastes of plastic, smoke, Chloraseptic, or Band-Aids, then look to these potential sources.