Esters and Phenols in Beer. What are they, and what do they contribute? Part 2

You may be wondering, what exactly is a “phenol”?

Let me start off with a quote from a contributor to the Journal of The American Society of Brewing Chemists, CW Bamforth. Bamforth says: “there are few more intimidating topics in brewing science than that of polyphenols; the complexity is immense”

That’s not scary or anything, NAH! Luckily, today I will attempt to simplify this for you and distill it down to the info you really need to know.

So, what is the definition of a “phenol”? well, broadly, a “phenol” can be any of a family of organic compounds characterized by a hydroxyl (―OH) group attached to a carbon atom that is part of an aromatic ring.

Phenols are like alcohol but form stronger hydrogen bonds. Thus, they are more soluble in water than are alcohols and have higher boiling points.

So now that the technical definitions are out of the way, what do phenols in beer mean to us?

To put it simply, phenols or “phenolic flavors” are usually described as clove-like, spicy, smoky or in worst-case scenarios, band aid- like or rubbery and medicinal.

Phenolic flavors can be an innate feature of specific brewing yeasts such as Wheat yeasts and other Belgian yeast varieties. Beyond those styles, phenolic flavors are using considered as “off”.

Let’s use the clove-like flavor that comes from Hefeweizen beers as an example. Wheat yeasts can target a specific acid found in malt called “ferulic” acid, into a compound called 4-vinyl guaiacol. So actually, while the primary precursor for this phenol comes from the malt (specifically wheat malt in the highest concentrations, as opposed to barley which produces less) This transformation cannot occur without yeast that is capable, though it’s the genetics of this chemical conversion process. This is how we are still able to brew wheat-based beers, with low phenol production, by using a yeast less likely to catalyze the transformation.

It’s also important to remember that phenolic flavors can also come from wild yeasts, either intentionally, or unintentionally via unwanted infection.

There is yet another way you can end up with phenolic flavors in your beer, and it’s no fun at all.

Enter something called a “chloro-phenol”, what in tarnation is that?! That is phenol created by chlorine… yep, the same chlorine you might find in pool water.

So how does this happen? Chlorophenols occur when chlorine is present, usually from the brewing water itself but sometimes it can come from cleaners containing chlorine, too. That chlorine bonds itself with the low molecular weight phenols found in malts to produce a Chlorophenol. This is the “phenol” that brings us that awful, burnt band-aid, medicine flavor. And yeah, it’s as gross as it sounds.

Luckily, that risk can be eliminated by not using chlorinated brewing water or cleaners that leave chlorine residues.

Now I think this next part is worth mentioning, for our All-grain brewers out there. Believe it or not, excessive phenols can also be extracted from malt during the mash and sparge program. The phenols created through this are called “polyphenols” or sometimes “tannins”. If you are an all-grain or even partial mash brewer, you can reduce the incidence of the “polyphenols” by simply lowering your sparge temperature below 170 degrees, and by using brewing water with low alkalinity and or residual alkalinity.

If you are steeping grains, and you find yourself getting acrid, sharp tannins in your finished product, try lowering your steep temperature just a bit, this reduces the extraction of tannins coming from the grain husk itself. These astringent tannins serve a purpose for the grain, in that they help to protect the “seed” from fungal infection.

So, is there anything positive about phenols outside of them tasting nice in specific beer styles? There is! According to published scientific consensus documents, studies have shown that the phenols in beer and wine, may actually be good for your heart! Here’s a quote from the abstract: “A large evidence-based review on the effects of moderate consumption of beer on human health has been conducted by an international panel of experts who reached a full consensus on the present document. Low-moderate (up to 1 drink per day in women, up to 2 in men), non-bingeing beer consumption, reduces the risk of cardiovascular disease.” In fact, the Managing director for Cooper’s brewery, Dr. Tim Cooper, is a cardiologist! So… if you needed a good excuse to enjoy that nightly brew, now you have it!  You’re welcome.

Keep in mind, however, this only applies to wine and beer and not to distilled spirits. Sorry guys!

Fortunately, science has taught us that phenols protect LDL against peroxynitrite-mediated oxidation. In short, they act as antioxidants! YAY beer! As a side note, if you wish to learn more about the healthy aspects of phenols, I highly recommend checking out the work of Ph.D.’s, Christy Tangney, and Heather E. Rasmussen.

All being said, there are too many individual phenols and polyphenols to name them all here. But this should tell you what you need to know for the purposes of brewing delicious beer as well as a bonus justification for drinking it.

All right guys! That about wraps it up for today! Thank you for hanging out with me again, and nerding out on my favorite thing, BEER! We’ll see you next time!