Dear Mr. Wizard,

The last two batches of beer that I brewed kind of tasted like Anbesol. I don’t think rinsing is my problem, because I rinse my equipment at least five times after sanitizing. The last batch was fermented in a brand-new glass carboy. Do you think that the trub that settles on the bottom of my carboy could be the problem? Or could it be the pellet hops that I used? I do siphon the wort through a funnel with a screen, so I really don’t get that much trub settling. Please help me; I’m going nuts over this.

Dan Dow
Easton, Pa.

Mr. Wizard replies:

Mmm, Anbesol beer! Two of the keys to problem solving in brewing are having a good palate and having the ability to describe what you are detecting with your senses. Anbesol is a phenol-based local oral anesthetic (like Chlorasceptic). There are several things that can make a beer taste phenolic.

The sanitizer problem you refer to in your question is the reaction between chlorine sanitizers and phenolic compounds found in normal beer. The result of this reaction is chlorophenols. Chlorophenols have a very low flavor threshold (they can be tasted even when they’re present only in small quantities) and taste nasty.

Certain malts can also impart phenolic flavors to beer. The most notable example is peated malt. Peated malt is intended for Scotch whisky, not for beer, but some clever brewer started a wave of "Scotch" ales brewed with peated malt. These beers are truly nasty (in my opinion).

Some highly roasted malts also have a phenolic flavor, but the intensity of the flavor is nowhere near that of peated malt.

However, the most common source of phenolic flavors in beer comes from yeast. Some yeast strains produce phenolic flavors as a normal part of their metabolism. These strains have enzymes that other brewing yeast lack. The phenolic flavors originate from phenolic acids naturally found in malt, especially ferrulic acid. Strains of yeast with the right enzymes transform these phenolic acids through a decarboxylation reaction into aromatic phenols, such as 4-vinyl guaiacol. These compounds are often described as possessing clove-like and vanilla aromas. Yeast used to brew Bavarian weizen beer is supposed to produce these aromas, and weizen beer is the best beer to buy if you want a standard for the phenolic flavor. Some Belgian and English ale yeast also produce detectable levels of phenols in beer. Phenolic aromas are not associated with most lager yeast.

In general, brewing yeast strains do not produce enough phenolic aromas to be detectable. Phenolic beers are usually a sign of wild yeast contamination. Wild yeast can get into a brewery fermentation through poor sanitation practices or can be dumped in the fermenter in high numbers if the pitching yeast is contaminated. Contaminated pitching yeast is not uncommon, even if you use "fresh" yeast from a packet. In general dry yeast contains wild yeast more often than liquid yeast, but both forms are capable of being contaminated. If I had to pick a likely cause of your problem, I would nominate your pitching yeast as the culprit. Try using a different strain from a different yeast company. If the problem doesn’t go away, then you need to work on the other causes of the dreaded phenolic aroma.

Mr. Wizard, BYO's resident expert, is a leading authority in homebrewing whose identity, like the identity of all superheroes, must be kept confidential.