While drinking beer is supposed to be about pleasure, tasting beer sometimes involves a certain element of pain. Beer is not always perfect. Not every beery flavor is delicious, and as tasters our job is to make note of every sensation we find, not just the happy ones. Beer is a fragile product, vulnerable to the whims of nature, easily tainted by tiny wild beasts, poorly tended tap systems and, more than anything else, the passage of time.
Stale beer is the brewing industry’s No. 1 technical problem, costing millions of dollars every year. Staling turns beautiful freshly brewed beer into a disappointing soup of blandness punctuated by notes of cardboard, decaying apples and other unpleasantness. There is probably more funding and experimental science going on in this area than just about anywhere else in brewing. And why not? Every brewery—wild and sour beers excepted to some degree—must deal with the issue of stale beer in the market. The stakes are high.
The life-sustaining air that surrounds us is deadly for fresh beer. Even though oxygen and time are the major actors, the stage is set long before bottling day, reaching way back to the chosen breeds of barley and the conditions under which they were grown. Being only a dabbler in this complex and highly technical area, I will attempt only a brief summary and hope no real brewing scientists are reading. Lucky for me there is a limit to the length of this article.
While brewers typically place a six-month shelf life on their products, the reality is that most of us can taste deterioration much sooner than that. Lauren Salazar has her tasters at New Belgium Brewing Co. so finely trained on stale flavors that they can differentiate between Fat Tire fresh off the bottling line and the same product just a week old. Even if we can’t identify specific off-flavors, we often grapple with beers that just seem a little dull and drab, lacking bright, fresh aromas and that sense of life we value so highly. Hops are especially vulnerable to the decay of freshness. Both bitterness and aroma fade, perhaps by as much as half in just a few months.
Beyond the simple wasting away of fresh, bright flavors, other changes pile on layers of weird fruitiness, beeswax and unwelcome sweet breadiness, topped off by a flavor that is universally described as wet paper, with nuances of shoebox, often accompanied by a drying, astringent finish, caused by an aldehyde—trans-2-nonenal—that is the most characteristic flavor of a beer in the final throes of old age. This paperiness may be apparent in the aroma, but is usually more obvious in the taste, especially at the finish. It’s not pleasant.
Other aldehydes and several esters accumulate over time, obscuring beer’s more subtle aromas. Overripe apple can be common, along with a sickly sweet honey/beeswax notes and sometimes a hint of aniseed.
For the übergeeks out there, here’s a little more detail: Oxidation of lipids, or fats, is one of the prime movers here, but there are many compounds in malt, hops and beer that play active roles in the process. There aren’t a ton of fats in malt, but as they oxidize into potent flavor chemicals, a little goes a long way. Some dark malts (and caramelized wort as well) are rich in chemicals that act as reductones, absorbing and later releasing oxygen. The caramel/crystal malts are especially suspect, and those in the middle of the range (about 60L) seem to be the most problematic. Beyond the weakening of aroma and bitterness, hops create other problems. Their aromatic chemicals morph into something called damascenone, which has a sort of a currantlike fruitiness that is not as pleasant as it sounds.
The keys to fresh or stale start quite early in the brewing process—out in the barley fields, in fact. And all through the malting and brewing process, the choices that maltsters and brewers make about the ingredients and processes used affect the way beers age. The liabilities continue through fermentation and especially packaging, and even in the bottle the beer is extremely vulnerable to the whims of those who transport, store and sell it. It’s the reason that lighter imported beers like pilsners in the United States rarely taste anything like they do in their home countries.
Various types of barley and malts differ in their vulnerability to oxidation and staling, but no matter the recipe, brewers must be careful during brewing not to offer easy access of air to the hot mash or wort, as exposure to oxygen anywhere in the brewing or packaging process lays the groundwork for later staling.
It is so important that packaging managers are sometimes given bonuses for keeping oxygen pickup at acceptably low levels. This is one of the biggest differences between small, semi-manual bottling equipment and larger more sophisticated lines. Equipment quality can dramatically affect the shelf life of packaged beer. Heat is also the enemy, as it accelerates all the chemical reactions. Beer will age twice as fast at room temperature than it will perhaps 15 degrees F cooler at cellar temperatures, and just a few hours at elevated temperatures can add months’ worth of normal aging.
There may be visual clues as well. For filtered beer, any haziness is likely a result of coagulated protein that manifests first as a simple haze and in extreme cases as little flakes that turn the whole bottle into a sort of a snow globe. It’s not harmful, but it is a sign that the beer is way past its prime—many months or even years.
Unfiltered or bottle-conditioned beers contain yeast, which is a pretty good scavenger of oxygen. As a result, this type of beer ages a little more slowly, but a bit of yeast in the bottle is no panacea. The same group of off-flavors found in filtered beers will show up in these as well. Yeast itself can also contribute its own flavors as it breaks down and releases chemicals from inside its cell. These may taste soapy or a bit toasty like vintage Champagne, or perhaps a bit brothy like soup stock. With beers aged for years, some umami tastes may show up as a bit of soy sauce flavor.
In a big beer, aging can be beautifully graceful, as bright hoppy or fruity flavors fade to a dry, burnished maltiness, sometimes with a sort of leathery tang or a pleasing port or sherry character. These qualities develop only after several months in the bottle and can continue to evolve in a delicious way for years if the beer is strong and well-brewed. A few years ago I tasted a Yorkshire beer that had been aged carefully since 1958. It seemed only a few years old, but such beers are quite rare these days, although older literary references abound in descriptions of beers that were decades old and as fine as any liquor.
Sadly, however, the vast majority of beers are like flowers blooming in the sunshine. Each has its brief moment, and then, poof, they become reminders of the swift passage of time, and of the importance of seizing the moment and enjoying every sweet, fresh, delicious drop.
This column appears in the January 2015 issue of All About Beer Magazine. Click here to subscribe.
Randy Mosher is the author of Tasting Beer and is a senior instructor at the Siebel Institute.