Shelf Life refers to the length of time during which a beer will stay in a desirable state in the trade. Frequently it is used synonymously with the term stability.

Most beers start to deteriorate from the time that they are bottled. While it is true that some beers, especially stronger varieties, can change over time in ways that lead to interesting and desirable flavors (via reactions similar to those occurring in some wines) most do not. See aging of beer.

The shelf life of a beer may be declared on the label, in terms of a “Best Before” date or a filling date. The former refers to the date before which a product is ideally consumed. The latter gives the date on which the package was filled, usually with an injunction regarding how many days the beer will be in its best condition.

As beer is inherently resistant to contamination by pathogenic bacteria, there is no health risk associated with consuming it after the shelf life has expired. Indeed, in many markets some beer has certainly seen its best days well before the end of the allocated shelf life. “Best Before” dates are probably more frequently set on the basis of the time within which the brewer is confident that the beer will not develop undesirable turbidity. The time may even be nothing more than an “artificial” declaration driven by logistical considerations, with not even lip service paid to the flavor quality of the liquid in the container.

The shelf life of beer will depend on the packaging type, ranging from a matter of days for cask- conditioned ale once it has been broached, to several weeks for a kegged beer, to months for beer in bottles and cans, with the latter enjoying the advantage of the most airtight seal.

The instability of beer takes various forms, including susceptibility to certain spoilage organisms, sensitivity to light, and proneness to gushing. However, the most extensively studied forms of instability are colloidal (haze, non-biological) instability and flavor instability (staling). Of these, the biggest challenge by a wide margin is flavor instability. See colloidal haze and flavor.

Even though many modern consumers equate crystalline clarity with quality in beer, the achievement of haze stability still seems to elude some brewers. See haze. While both beer drinkers and laboratory methods can agree upon the question of whether a beer is clear or not, there is more debate about the desirability of clarity. Interestingly, there are regional differences apparently developing in the mind of the consumer. In the eastern United States, for example, most beer drinkers expect sparkling clarity in most styles of beer, whereas many in the west of the country regard clarity with suspicion, suspecting that the beer is over-processed.

Among brewers there remain deliberations centering on the merits and demerits of downstream stabilization methods.

Flavor instability is altogether a more complex issue, stemming at least from the fact that a perceptible change in the level of any single flavor component may be construed as instability. Considering there may be some 2,000 flavor active species in beer, many of which display extremely low flavor thresholds, the problem is manifest. Even if brewers take a more conservative approach and suggest that far fewer compounds than this are significant through their changing levels during beer storage, the range of substances is still substantial. Confounding the situation further is the reality that, whereas most brewers deplore classic aged character (cardboard/wet paper flavors and aromas), there appear to be a very many customers who either don’t recognize it, don’t care about it, or even might desire it (this mirrors winemakers’ experiences with cork taint, a problem that affects a fairly high percentage of wine bottles, but goes unnoticed by many wine drinkers). They are used to this aroma in their beers, often because the beer has travelled a long way for a long time to reach them. It has even been suggested that beers should be stressed to their ultimate, achieving aged character before leaving the brewery, with the intent of training the customer to accept aged character as the norm. That would certainly overcome the fundamental problem for brewers: if customers are accustomed to fresh beer, then it is desirable that they should always receive it in that condition, despite the enormous challenges involved. However, if customers are used to drinking a stale product (for example one that has been imported and which has traveled vast distances with agitation), then they will expect that flavor (rightly or wrongly depending on the brewer’s philosophy). It is amusing to note that the term “stale,” as applied to beer, was once a term describing a desirable aged quality, not the epithet it has become today.