So we’ve seen some of the basic flavors in beer and from they originate. Other flavors and aromas persist, though, and these aren’t so good. Let’s take a look at some of the common ones now, and how they invade your beer. Bad flavors originate from different sources. From the brewing method, to storage, to serving and sometimes drinking.
Perhaps the most popular bad taste is the ‘skunk’. This is a particular taste (and smell) that is akin to the skunk’s, uh…defense mechanism. There are two main causes of this:
One: The beer has been ‘light struck’. This means that light (ultraviolet and visible) motivates present riboflavin to break apart certain hop molecules. In turn the free pieces attach to sulfur atoms to produce the skunkiness. Certain brewing techniques (e.g. Miller) use a different hop extract lacking these certain molecules and is thus more resistant to skunking. To protect against light, some breweries use brown bottles or enclose their 6 and 12 packs with more cardboard packaging. Some have even moved to canning their beers, a trend gaining more and more momentum as canning technology advances. Green and clear bottles offer minimal, if any, protection from light.
Two/a: To assume a skunked beer is the result of light damage is just that, an assumption. In fact some beers are designed to offer tastes similar to that of skunkiness. While similar in taste and smell to skunked bottles, these beers derive their taste from natural sulfur tendencies in yeasts or hop strains used in brewing. So, if you taste a beer that has a skunkiness characteristic, it might be due to light damage, or as the brewer intended.
Two/b: You could find yourself sipping a beer from a glass at a restaurant, a brewery, a party or by yourself outside, enjoying the sun. Chances are, if you are in the straight sunlight for more than a minute or two, your beer will suffer from the beginnings of light damage. The beer might taste different from start to finish. It ain’t the beer’s fault, it’s the lucky ole sun.
Diacetyl: This a volatile compound found in the fermentation. While low levels can give a beer a “slick” feeling in the mouth, it is most noticeable at high levels as a butterscotch flavor. This can, in large part, due to poor maintenance of tap lines. Diacetyl can absolutely ruin a beer.
DMS (dimethyl sulfide): This volatile compound is developed during the brewing process from the malt at high temperatures. During boil the DMS is expelled, but as soon as the boil stops DMS builds up again and the wort must be cooled quickly to limit its presence. DMS will give off a cream corn aroma and slight taste. While this may be normal, in small amounts, in some lager it is most commonly an error in brewing and sometimes by infection.
Chlorophenol: This is a plastic-medicine like aroma, kind of like a Band-Aid. It’s more prominent in the aroma than taste when present and is due to residual cleansers and sanitizers in the beer. Could also be a yeast problem.
Those are the more common imperfections in beer. So the next time you taste or smell some of these you will be able to identify what may have happened to the beer and if it's avoidable next time you try that particular brew.