Through a Glass Darkly

I seem to read more and more articles by beer, and other beverage, writers extolling the virtues of the widening range of bottled beers available to the British drinker. Very good, so far. However, I get more and more disenchanted when I read many of them recommending beer bottled in green or clear glass. If you know why, you have no need to read further but if you ask 'why?', you really need to read this piece.

For over 100 years, brewers have known that when beer is exposed to light, particularly in the range of 350 - 500nm , it affects certain hop components in the finished beer. In most places in the world this is known as the 'Light-struck' effect. However, because the chemical that is formed, mercaptan thiol (or MBT), is the basis of the defensive odour given off by skunks, American brewers and beer drinkers call affected beer 'Skunked'. To make matter worse, MBT has an extremely low taste threshold which means that the smallest amount in beer makes its presence noticeable.

This photo degradation is minimised by the use of dark brown glass bottles, which filter out this dangerous light but green or clear bottles give little or no protection. Obviously, the strength of the light affects the process but even here MBT takes no prisoners. Direct sunlight will cause the reaction in 5 minutes, fluorescent light a few hours and normal, incandescent, lighting takes a little longer.

So, why are brewing companies packaging their beer in green and clear glass? Because their marketing departments have found that most bottled beers are bought, particularly in supermarkets, by women and that they, the young and trendy and, frankly, the ignorant, think that brown bottles are fuddy-duddy and that green and clear are more attractive. The marketing people wear down the brewer's objections and, of course, sales are good, the marketing people win again and the brewer takes bottles of his beer home in cardboard boxes and keeps them in the cupboard under the stairs or other dark place. That's also what I do when I buy Pilsner Urquell.

There are two ways round the problem; one is to use a hop extract which has been chemically modified to prevent the reaction and the other is to use an expensive light-filtering sleeve over the bottle. There may be some UK brewers using the extract but I do not know of any using the sleeve technique. However, most of the new interesting bottled beers come from small breweries that boast of their 'traditional' brewing methods - I can't see them using the fact that they use 'chemically modified extracts' instead of real hops as a USP!

You don't believe me? Speak to Peter Ogie or read 'Brewing' by Ian S. Hornsey, (A micro-brewer and chemist) published by The Royal Society of Chemists, 1999.

Why do I have a particular bee in my bonnet about this? Some 15 years or so ago I learnt about this 'light-struck' effect from a talk given by the then Quality Manager of Whitbread. That weekend I stood by the recycling bins, feeding them with over 100 pretty green and clear bottles, which I had laboriously de-labelled, cleaned and sterilized. You don't forget such an experience!

James McCrorie - September 2001. Originally published the British Guild of Beer Writers' Newsletter