Aging Of Beer, an aspect of beer connoisseurship that is rapidly being rediscovered by modern breweries, beer enthusiasts, serious beer bars, and restaurants. Here we must distinguish aging from two other terms: maturation and staling. The term maturation refers to the relatively short controlled aging period employed by the brewery to transform freshly brewed “green beer” into a drink suitable for sale. Traditionally this maturation takes place over a period as short as 1 week or, in the case of certain beers, a few months. Staling refers to the onset of unwanted and unpleasant flavor, aroma, or appearance caused by inappropriate aging and/or exposure to heat, light, oxygen, and other harmful factors.

Beer aging, on the other hand, is deliberate, or at least felicitous. Many wine enthusiasts are of the opinion that wine is the only beverage that can benefit from aging, but this is not nearly true. In fact, the vast majority of wine is incapable of aging well and is designed to be consumed as soon as it leaves the winery. If aging is attempted, these wines will become stale. Precisely the same is true of beer—most beer is at its best the day it leaves the brewery and, depending on conditions, it has a limited shelf life, often measured in months and rarely exceeding a year. However, certain beers, kept properly, will improve and deepen with age, becoming increasingly complex and even profound.

Whereas most beer throughout history has been meant for consumption within days, weeks, or a few months, certain beer types have always been meant to age further. One of these is Belgium’s range of lambic beers, complex and acidic wheat beers entirely fermented by wild yeast and bacteria living in the brewery and its environs. See lambic and wild yeast. Lambics and similar beers have probably been made for more than 1,000 years and are traditionally aged in oak barrels. One or two years of aging in barrels is normal for lambic, and bottled styles such as Gueuze can age for many years further. Because of the interactions between its complex microflora, the aging of lambic is unique among beers. In some ways it resembles the aging and affinage of cheese, where continued action by bacteria and molds will help develop the cheese to the height of its flavors. In lambic, the microflora represent the biggest influence over the period of aging, but other factors are at work as well.

Oxidation, although usually considered a form of damage at virtually all stages of the brewing process, is an important part of the deliberate aging of both beer and wine. The difference between unwanted damage and desirable evolution is both qualitative and subjective. Beers that cannot age well, such as pilsners, are admired for their fresh, bright qualities, all of which will eventually be lost over a relatively short period of time. In such beers, oxidation tends to be rapid and somewhat violent, replacing malt flavors with unpleasant notes of black currant or tomato, followed by an impression of wet cardboard. These negative changes tend to be accelerated and compounded by dissolved oxygen in the original beer, oxygen in the headspace of bottles, and elevated aging temperatures (above 20°C, or 68°F). Certain esters will decrease in aged beer (such as banana-like isoamyl acetate), but other esters tend to increase, leading to wine-like flavors. Hop bitterness decreases over time, as does hop aroma. Hop aroma tends to degrade first to tropical fruit-like flavors, which can be pleasant, but then to less desirable tea-like flavors.

In beers that are age worthy, such as barley wine, slow oxidation and breakdown of various compounds will create a different set of new flavors as the old ones recede. Barley wine is a beer style that was originally designed to age and was traditionally never consumed young. See barley wine. In such beers negative flavor developments, if they arise at all, may be masked by more powerful positive aromatics within the beer. Rich bread-like malt flavors can become nutty and then toffee-like, eventually oxidizing to almond-like flavors reminiscent of sherry. Further aging can bring on leathery flavors that can be harmonious with the whole. Roasted malt character can change from “fresh coffee” to “dark chocolate” and eventually to “rich old Madeira,” picking up complex licorice notes along the way.

Many factors of beer aging are non-oxidative and not fully understood. As compounds break down, the components become available for new reactions, and new flavors, mostly esters and aldehydes, are formed in a fashion that can be difficult to predict. In bottle-conditioned beers, the complexity is compounded by presence of yeast. While the yeast remains alive, it can slowly synthesize new flavors, and the flavors of the beer may become more profound. The eventual death of the yeast can result in more typical “meaty” or “soy sauce” autolysis flavors, but it can also result in the toasty hazelnut- like aromatics that are highly prized in vintage Champagnes. Over time, however, bottle-conditioned beers tend to lose their foam stability because enzymes released by yeast autolysis break down the proteins responsible for foam formation. Old bottles of strong beers such as barley wines and imperial stouts can also throw a crust of sediment, even if the beer was originally filtered. Therefore, old bottles should be kept upright for at least 24 hr before pouring and then poured carefully to avoid sediment in the glass.

Although beer aging is highly complex, we do know that some beer types tend to age better than others. Strong beers tend to be more age worthy than beers that are lower in alcohol. Beers that age well tend to have relatively high hop bitterness, but are more malt forward than hop forward in their aromatics. Relatively high residual sugar confers an advantage (barley wines, imperial stouts, old ales), but some dry styles can fare well. Strong dark Belgian Trappist and abbey ales, for example, tend to age well, despite their relative lack of residual sugar. Although it is not always true that darker beers age better than paler beers, it does tend to be the case, with lambic styles and some Belgian tripels as notable exceptions. Pale beers tend to darken over time, but dark beers may become slightly paler as their color compounds combine with other elements and sediment out. As with age-worthy wines, beers that are destined to be beautiful after 10 years or more of bottle age will tend to first experience a tough, inexpressive, and disjointed youth.

Although slow oxidation can be positive, rapid oxidation is almost always negative for beer flavor, and brewers wishing to see longevity in their beers will avoid oxygen pickup throughout brewing and packaging.

The best storage conditions for aging bottled beer are similar to those for aging wine. Most beers age best at “cellar temperatures” of approximately 11°C to 13°C (about 52°F to 55°F). Colder temperatures will retard the aging process; much warmer temperatures can accelerate aging, but the results will tend to be less pleasant. Bottles of beer should be stored upright and in the dark. Aging wine bottles on their sides prevents drying and shrinkage of corks, but this is generally not a problem for beer because most beers are sealed with either a crown cap or a compressed Champagne-style cork. Very old bottles will sometimes be closed with straight corks, but these are often covered in wax to prevent shrinkage and ingress of air. Most beer enthusiasts are not blessed with perfect conditions for beer aging at home. At home, often the best that can be done is to keep the beer in a dark place where summer temperatures are moderate. Intentional aging of beer in kegs is far less prevalent than aging of bottles. However, well-brewed kegged beers can store well, usually at relatively cold temperatures (around 4°C [40°F], the average temperature for normal storage of non-pasteurized kegged beer), for 10 years or more.

As interest in “vintage beer” grows, many brewers have started printing the production year on the labels of their age-worthy bottles, a practice that was previously limited to a small number of breweries. Some high-end restaurants and enthusiast bars feature vintage beer collections, but supplies are naturally limited. Today, breweries sometimes struggle to provide the market with enough aged beer, so many are establishing their own in-house aging regimes, not too dissimilar to those of good wineries.

Although barley wines and imperial stouts aged for 10 or 20 years are not unusual, some beers possess considerably greater longevity. In 2006 the Worthington White Shield Brewery at Burton-on-Trent found some 200 bottles of Bass Ratcliff Ale 1869, a barley wine brewed to commemorate the birth of a member of the Ratcliff family, who were partners in Bass. The 137-year-old beer was found to be in astonishingly wonderful condition and reminded tasters of a fine old Amontillado.

See also bass & company and imperial stout.