It is important to note, not all aging is negative. When it comes to finished beer, dark malts tend to condition especially well, expressing deep complexity over elongated periods. Styles with certain spicy or peppery phenolic compounds may transform to soft tobacco, leather, or vanilla. Hops will fade, inevitably, but this can focus attention to body and mouthfeel. Even oxygen can contribute some benefits with the development of wine and sherry like compounds.
After nearly a year of practical analysis, many brewers expressed new questions about extending stability. Resources on the subject are extensive, but details can be overwhelming. In a brief overview, we will discuss what brewers can do to help improve the life of their finished goods.
In order to stabilize beer, simply reduce the number of active changes taking place. Of course, this is easier said than done. There are a number of avenues to pursue, however tradeoffs will always be made. Start with a process audit to confirm the critical control points, then identify areas of concern. Review each area individually for opportunities to improve.
First and foremost, I always suggest tracking Dissolved Oxygen levels. Although countless factors influence stability in your finished product, DO levels will have the largest impact by far. Oxygen reacts with many different compounds inside beer, changing the flavor, aroma, and appearance. Poor packaging practices can see a nearly perfect product fail sensory standards in a matter of days.
Oxygen is such a large concern that even raw material can be negatively affected. Nearly every brewer is familiar with hops that have been exposed to open air for extended periods, however many are unaware that crushed grain can undergo a similar transformation. As short as overnight, milled grist can react with oxygen to “stale” product. Ultimately these changes lead to reduced shelf-life in finished product. Take extra care to preserve your raw materials!
Most brewers are well familiar with the concept of “stabilizing” yeast, either through fining, filtration, or centrifugation. Perhaps uncommon today is the use of metabisulfites to inhibit fermentation activity. Even less common is the use of non-thermal high-pressure pasteurization (HPP). Regardless of technique, the concept is the same; less biological life means less changing in the finished beer. Pasteurization is a traditional favorite, but some rebuff the flavor compromise.
Microbiological stabilization is supremely important, however if care is not taken, yeast can be “inactivated” prior to full maturation of the wort. A proper fermentation is essential to long-term stability, so quantifying DO levels in cast out wort helps tremendously. Some yeast strains are prone to early flocculation and may drop out of suspension before re-metabolism of Vicinal DiKetones (VDK’s) can occur. In these cases, it may be necessary to take extended measures such as rousing or krausen to reach an acceptable threshold.