I decided to do some research on the mystery taste that I experience whenever I choose to drink a pilsner or German lager. What I found, while not really great news, certainly explains my previous findings in a reasonable manner.

“Whoa! This beer is skunked!” is probably something you’ve heard before, uttered by someone who was probably drinking a green-bottled Heineken. And from the guy who thinks he knows something about beer: “That’s because it’s in a green bottle, dood.”

Not quite, junior beer guru. That so-called “skunked” character has nothing to do with green bottles, or any color bottles. True, some beer bottle colors are more susceptible to being what’s called “light-struck,” however, the whole idea that the color is the cause is completely wrong.

What does light-struck mean?
This is when the beer has been exposed to ultraviolet light for a period of time. Hop-derived molecules, called isohumulones, are basically ripped apart. Some of these parts bind with sulfur atoms to create that “skunk” character, which is similar in character to a skunk’s natural defense and is such a potent compound that parts-per-trillion can be detected and even ruin a beer. Although brown bottles aid in protecting beer from being light-struck, it hardly makes the beer invincible. Green or clear bottles provide little to no protection. And it’s been said that bottled beer can become light-struck in less than one minute in bright sun, after a few hours in diffuse daylight, and in a few days under normal fluorescent lighting.

This light-struck condition is often to blame for a skunked beer. Many popular imports are distributed in green bottles. Pair the two, mix with misinformation and an inexperienced palate, and the common belief becomes that if beer is in a green bottle, it has to be skunked.

Yeah, but everything I drink from (a green bottled, imported beer) tastes skunked.
Well, it’s not like there’s an international conspiracy by the brewery to expose all of its beer to being light-struck before being sold. Breweries are not in the business to sell spoiled beer. And did you ever consider that that’s the how the beer was intended to smell and taste? The natural and often times wanted sulfur character produced by certain strains of lager yeast, under certain beer style brewing conditions, does not make a skunked beer. Nor does a pungent hop character that you might not be used to. Don’t confuse these characteristics with being skunked, as it’s not always the case.

Yeah, but it’s always skunky in the bottle and not the keg.
Drinking from the bottle is a more concentrated experience. Drinking from a glass allows the beer’s characters to become more volatile, thus a less concentrated experience. It doesn’t necessarily mean that the beer in the bottle is skunked.

How can I avoid skunked beers?
Simple. Don’t buy beer on display, don’t buy beer in a cooler that is brightly lit and don’t leave your beer exposed to light.

So there you have it. Just remember that before you give up on a beer and write it off as being skunked, keep in mind that there’s a lot more that could be going on, and that perception of characters is highly subjective. What you might call skunked due to lack of knowledge could be a tasty German-style Pils to another.

Source: Skunked Beer @ Beer Advocate

It turns out that some beer (often in green bottles) uses a yeast strain which produces a sulfur flavor in beer. This is what I dislike. The reason it tasted so much better in a keg is that it is less concentrated. The yeast’s flavors are much more diffused in a keg, and much more intense in a bottle.

It doesn’t mean that beer in a green bottle is bad, though it does have a higher risk of being really skunked (or light-struck). If you want to avoid that, don’t buy beer out on display or in brightly lit coolers. Buy it in a case or 12-pack that is completely sealed. Or, if you are like me and don’t like green bottled beer at all, learn your beer types, and stay away from that style of beer.