Beer, Chemistry and Marketing, a violently exothermic reaction of the brain.

Television advertisements.

Some of them can be absolutely ingenious. Some of them can be incredibly annoying. And some of them can be unquestionably, mindbogglingly stupid. The latest marketing campaign for Miller Genuine Draft beer belongs to this last category.

You've probably seen the commercials. They portray someone in a tough situation where they are uncommonly open, and consequently resolve the situation to their benefit. This is complete with their marketing slogan: "Miller Genuine Draft is in a clear bottle because it has nothing to hide", showcasing their unique clear bottles. And it's those damn clear bottles that make this marketing campaign so stupid. It would seem that the folks at Miller forgot to hire a chemist or two for their marketing department, because beer is bottled in dark bottles for a reason.

One of the key ingredients in beer is hops. Hops contributes much to the flavour of beer, through a class of chemicals known as isohumulones. Isohumulones are in all types of beer, and are perfectly fine. They are not a problem by themselves. Problems can arise, however, because of another chemical found in beer: riboflavin.

Ribovlavin (better known as Vitamin B2) is found in all kinds of foods and beer is no exception. Unfortunately, riboflavin and isohumulones don't get along very well. Riboflavin tends to break down isohumulones, so having them both in beer can be problematic. Normally, this is not a big deal, though, because the chemical reaction whereby riboflavin degrades isohumulones requires a catalyst, and that catalyst is light. This is the reason why beer comes packaged in dark-coloured bottles. The dark colouration keeps out light, and prevents the isohumulones from breaking down.

Why is isohumulone degradation a bad thing? Well, when these chemicals are broken down by riboflavin, they form a compound called 3-methylbut-2-ene-1-thiol. This compound gives the beer a very, very bitter taste: the beer becomes spoiled (unless you happen to enjoy very bitter beer, I suppose). If this happens to beer, then it is often referred to as being "skunky". Little wonder why: 3-methylbut-2-ene-1-thiol is very similar to the compound used by skunks in their spray.

So beer that is bottled in clear bottles like Miller Genuine Draft (as well as Corona, and beers bottled in green bottles like Heineken) will end up spoiling and becoming very bitter much quicker than beers packaged in dark bottles.

So does Miller Genuine Draft really have nothing to hide? I think the fact that their beer contains skunk juice is something worthy of keeping hidden.

EDIT: It's been brought to my attention that Miller uses a strain of hops that contains a more light-stable form of isohumulone to prevent their beer from skunkifying when exposed to light. Nevertheless, the chemistry remains the same and is still interesting. Take note all you home brewmasters out there.