"Is There A Skunk In My Beer?" by Mike Sherlock

So let's say it is just before Thanksgiving and you're hosting a large group. If you're like me, you have stocked your refrigerator with lots of beer. Your wife says, "where am I going to put the 24-pound turkey? I can't fit it in there with all your stupid beer!" But you reply, "it's already cold. I can't take it out because then it would go skunk."

This is patently untrue.

Like many, I believed for a long time that temperature-shock spoiled beer. Surely, radical shifts in temperature can alter the taste of beer. But in order for this to happen, one would have to nearly boil the beer, quickly freeze it, boil is again, and freeze it again. So pulling some bottles or cans out of a (roughly) 42-degree refrigerator and letting them warm to room temperature (roughly 72-degrees) will not bother the flavor/aroma of the brew in the least. One may chill beer again after it has gone warm and the process won't affect it at all.

The actual cause of "skunky" beer is a nasty chemical compound known as MBT. That stands for 3-methyl-2-butane-1-thiol, but "MBT" rolls off the tongue a lot easier. In order to explain where this compound comes from, we must first discuss what goes into beer to begin with.

During the brewing process, brewers boil the unfermented beer (called "wort") and toss in hops. Hops are a vining plant and the female flowers (which look like adorable little green pinecones) impart both bittering and preservative characteristics to beer. The latter effect is why our ancient brethren originally added hops to beer.

Hops are rated by how much alpha acids they contain as a percentage of their overall weight. The more alpha acids that are in the hops, the more bitter a finished beer will taste (depending on the hop variety and how long they are boiled). But there are lots of different kinds of alpha acids. One particular kind is called isohumulone. When this alpha acid sees certain light (some UV and some visible light, caused by the sun or fluorescent bulbs), it reacts with the riboflavin present in the beer and forms MBT, leaving a sulphur-like flavor and aroma. This process can happen rather quickly and the compound may start to form after only 60-seconds of exposure to light. It doesn't matter what temperature the beer was or is kept at. MBT is actually the exact same chemical compound that a skunk excretes from glands located near its backside; hence the term "skunk beer."

One may have noticed that most bottled beers come packaged in brown glass. The reason for this is to ward off the effects of sunlight on the finished product. But some come in green, clear, or (to a lesser extent) blue bottles. Why would a brewer package their product in a bottle that would allow such a hideous chemical reaction to occur?

There are three reasons: 1) they already took care of it, 2) marketing, or 3) it's part of the flavor. To the first point, some brewers use hops that do not contain (or only have a limited amount) of isohumulone. So they (and the drinker) don't have to worry about it.

Some use clear or light-colored bottles because their brands lend themselves to a "Summer" or an "island" feel. Would you want to sit on the beach during a 90-degree day and drink a thick, heavy stout ale from a brown bottle? Of course not. So, in order to keep in line with their brand positioning, they use a clear bottle to showcase the light color and refreshing nature of their product. They might even convince you to stick a lime wedge in it to counteract the off flavor of MBT. I'm not naming names here.

Another reason why brewers might not be concerned is because a mild "skunky" flavor is what they actually want in the finished product. It sounds weird, but consider sourdough bread or sourdough pretzels. Why would someone want to eat something that's gone sour? Because it's just part of the flavor.

Look at some European imports that come in green bottles. They've made the trip all the way to the US in those bottles and have been exposed to at least some sunlight. Try drinking a Heineken, Grolsh, or Pilsner Urquell from a bottle and then drink one from a tap. The differences in taste and aroma should be obvious.

Homebrewers tend to only use brown bottles. Other colored bottles are OK, but one needs to carefully store them. Even while the beer is fermenting, sun and fluorescent (and even incandescent) light should be avoided.

The Lu Lu Brewmeisters always take the utmost care when brewing, bottling, and storing. Next time you see us, go ahead and have a bottle. And remember, there are no skunks in our beer!