Jason Foster

Check out more of Jason Foster’s beer news and views at onbeer.org

Think about sitting around enjoying a glass of beer. Maybe you are on your deck on a sunny summer afternoon. Or you are in a pub chatting with a few mates. Something you are not likely to be thinking about is how the bottle or glass that your beer comes in might affect the taste.

Well, it can in the most telling fashion. In the wrong container, your delicious beer could quickly turn into something undrinkable. The wrong colour of glass can create the most unpleasant beer taste imaginable. Allow me to explain.

In short, if a beer is not protected by the right kind of glass, it quickly becomes “light-struck”, or in the beer biz what we call “skunked”. Beer, as it turns out, is very sensitive to light. Or, more accurately, the hops in beer are sensitive to light.

Here is what happens. Hops contain something called alpha acid, the substance that gives beer its bitterness. When dissolved in beer it isomerizes and turns into something called iso-humulone. Beer also naturally possesses undetectable trace amounts of sulphur.

When iso-humulone comes into contact with light, it triggers a photo-chemical reaction with the sulphur to create 3-methyl-2-butene-1-thiol - not a very pleasant compound. In fact, it is the same substance skunks spray to ward off attackers. Yummy!

The reaction can happen very quickly. Exposure to the sun of even 10 or 15 minutes will create noticeable levels of this compound. Leave an unprotected beer in the sun for a few hours, and it will taste and smell of skunk to almost any palate. This effect happens in both natural and fluorescent light.

If you don’t believe me, try it yourself.  A few years ago in preparation for my beer judge certification exam, I intentionally skunked a beer to familiarize myself with the taste. I put a clear bottle of beer in the sun for 12 hours. Upon opening skunk aroma filled the room in seconds. I will never forget the horrid taste and smell.

Before you panic, there is some good news. This reaction only occurs with light wavelengths closer to the violet spectrum. This means something can be done. Brewers have discovered that brown beer bottles filter out the offending wavelengths and the beer is protected from skunking. That is why most beer is bottled in brown glass.

You may see where I am going with this. Clear or green bottles are no help whatsoever to prevent skunking. Which naturally leads to the question - what about those beers in clear or green glass?

Quite frankly most of them are skunked before you even buy them from the store (since most stores are lit by fluorescent light).  Maybe, luckily, you buy it soon after it hit the shelves and the skunkiness is mild.  At low levels it can add a sweetness and silkiness to the beer. Or more likely the beer has been sitting on the shelf for three weeks. Skunk-a-rama! There is a reason why some of those companies advise adding lime or lemon to the beer. The fruit masks the skunk with strong citrus flavour and aroma.

If you are perplexed by the thought of professional brewers packaging their beer in a fashion that guarantees it will develop off-flavours, I share your confusion. The explanation is, unfortunately, rather cynical. A while back I had a chance to ask a European brewer why they put their beers in green bottles for North America (in Europe they use brown bottles). His response? North Americans apparently like skunked beer because it seems “European” to them.

The reason brewers use clear or green glass is marketing pure and simple. It makes the beer more attractive, especially if it is a summer-inclined brew. For Europeans, it is a way to distinguish themselves on the shelves as an import. They are all hoping that beer drinkers don’t notice.

Avoiding skunked beer is not that difficult. The easiest approach is to buy beer only in brown or other light-impermeable packages. If your favourite beer does come in clear or green glass, I suggest you do your best to keep it out of the light. Buy it fresh and keep in an enclosed container until consumption.

This can be a challenge. Even in the best liquor stores the beer cooler is lit by fluorescent lights, and the beers sit exposed on the shelf. Try encouraging them to package clear and green bottles in cardboard box or similar solid container.

Beer in mugs and pint glasses can be more difficult. At home on a sunny day, go for a ceramic or opaque mug. On a pub patio, where you can’t choose your glass, just do your best to shield it from the sun and try to drink it as efficiently as you can. For most drinkers exposure of 30-60 minutes will not create noticeable off-flavours.

But mostly don’t let it wreck your enjoyment of the moment. Beer is supposed to be a relaxed beverage. Enjoy your friends and the time you are having. That is more important than some photo-chemical reaction.

This entry was posted on Friday, March 19th, 2010 at 7:40 pm and is filed under Beer 101 w/ Jason Foster. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.