The Dawn of the Obvious
As I reflected on what had happened, a pattern took shape in my mind that I should have understood a long time ago: When it comes to the care of rare and expensive beers, our beer stores and pubs are often frivolously dysfunctional!
Merchants do precisely the wrong thing when they allocate store space for beer. The fast-moving cans in a suitcase or the 40-ounce bottles of un-ruinable malt liquor are always in the cooler, while the slow-moving, most expensive beers are always out on the floor shelf, where they are exposed to permanent light and warmth. Yet, as professional merchants, beer store owners ought to know the most elementary truth about beer, one that any brewer has internalized as a core part of his professional credo, namely that beer is a perishable food commodity, one that does not get better with age, and one that undergoes flavor-destroying chemical changes when kept under the influence of light and heat.
With age, beer eventually becomes stale, hazy and skunky, a condition more likely to occur in slow-moving specialty brands than in ordinary, fast-selling mass brands. So consumers are paying the highest prices for the brews that receive the worst treatment.
Beer Aging Dissected
Light energy causes a photochemical process in beer, during which the hop’s bittering agents react with sulfurous fermentation trace elements and dissolved oxygen elements to form a revolting, skunky-tasting compound known by the impossible name of 3-methyl-2-butene-1-thiol. This photochemical reaction occurs both on warm shelves and in brilliantly lit coolers, and it is fastest in clear or green bottles, which cannot block the frequency of light that is most responsible for the process. Brown bottles have optimum (though not perfect!) blockage ability, but they, too, can only delay, not prevent, the inevitable. Skunked beer, therefore, is also termed “light-struck” beer.
Oxygen is another great enemy of beer shelf life. There is always a small amount of oxygen in solution in any beer. In addition, bottled beer picks up so-called packaged oxygen during the filling process. The amount of pick-up depends on the sophistication of the bottling and kegging equipment. The effect of oxygen on packaged beer is called “staling.” Among the key compounds that oxidize during staling are fatty acids (lipids), of which beer contains a few trace elements. The impact of oxidized lipids is disproportionate to their numbers.
The flavor sensation of staled beer is variously described as soapy, fatty, sweaty or goaty. Other oxidized products in beer may impart winey, wet cardboard, cooked vegetable, celery, sour or acrid flavors. Importantly, the rate of oxidation accelerates significantly with an increase in the beer’s storage temperature. For instance, a particular brew that may have a shelf life of four months if kept at a temperature of 42 degrees F may have a shelf life of less than three months if kept at temperature of 86 degrees F.
There are exceptions, of course. Among these are, for instance, high-alcohol bocks and eisbocks, such as Samichlaus and EKU 28; or barley wines, such as Sierra Nevada Big Foot or Thomas Hardy Ale. Many of these brews carry the “vintage” year on their labels and are intended to be “put down” for a few years. Like Madeira, port, and sherry, which are deliberately oxidized wines, these big beers seem to acquire their sought-after signature flavor only after oxidation. Yet even these heavyweights ought to be allowed to age gracefully in a dark, cool environment, not on a brightly-lit store shelf at room temperature. Even an old eisbock or barley wine does not benefit from light-struck skunkiness.
Finally, beer exposed to higher temperatures and plenty of oxidation also tends to develop of permanent haze over time. Hazes tend not to be present in fresh beer. Technically, such hazes are formed when beer loses what is called its colloidal stability. The haze occurs when normally invisible dissolved protein particles form a loose bond with polyphenols (from grain husks and hops) and become visible. All beers eventually develop such hazes, but the rate of haze formation can increase as much as five-fold in heavily oxidized, over-the-hill beers.
From these explanations, it ought to be clear that after six months on a warm shelf in a well-lit store, there is hardly a bottle of beer that is anywhere near the wonderful treasure it was when it left the brewery. Even the best of brews can become undrinkable. The breweries themselves, too, seem to understand this problem, as I learned during a lunch meeting in November 2000 with the then-head of the quality lab of one of the big Munich breweries. He candidly admitted to me that it is next to impossible to reconcile the brew-technical rules for making a great brew with the modern commercial imperative of having that brew last a full year on the shelf. This, he said, was his biggest quality challenge.