All hail the hop! It’s both a useful and tasty ingredient to your beer. It lends a wonderfully bitter taste to your favorite brew, while at the same time providing a wide range of fragrant aromas. It’s most important effect, however, may be as a preservative agent.

Hops have a unique ability to discourage the growth of bacteria that would otherwise sour your beer. Yeast cells are not effected by this hop antimicrobial effect, so they are allowed to ferment away in peace. Think of hops as providing an immune system for your brew. Brewers have long known about this preservative effect, and have used it to extend the shelf life of their product for centuries. The first IPA’s were brewed not for their flavor, but to make them hoppy enough to withstand the long journey from Britain to India (hence the name Indian Pale Ale). The great taste was almost an afterthought!

Hop flowers produce resins which contain a variety of different acids. These acids are responsible for the various effects of hops in beer. Typically, these acids are divided into two groups: alpha and beta acids. Alpha acids are primarily responsible for the bitter tastes of hops, while Beta acids provides the aroma. Both are thought to contribute to the antimicrobial effect.

When looking at hops from a beer aging standpoint, loss of hop smell is often the first thing noticed in a aging beer. The beta acids responsible for the hoppy aroma happen to be quite volatile, and simply won’t hold up long term in the cellar. Alpha acids will also degrade over time. You will inevitably notice your beer becoming less and less bitter the longer you age it. This is often perceived as a “smoothing” out of your beer. My 30-month old Celebration Ale has virtually none of the hoppy bitterness that was very apparent when the beer was fresh.

Despite losing hoppy flavor, you will probably notice some new tastes creeping into your brew that are direct results of this hop degradation process. Very commonly a “winey” taste is associated with degraded hops acids, which can be quite nice in the right beer. On the bad side of things, degraded hops can also sometimes be associated with an “old hops” flavor, mostly coming through as a cheesy kind of taste, which is usually not that pleasant. Degraded hops acids have also been shown to combine with ethanol to produce various kinds of esters, which we can taste as various fruity flavors.  This is one reason why beers in high ABV% are good to cellar; the higher levels of ethanol can lead to greater ester levels over time. Exactly how and what esters are produced as a result of these reactions are an area of continuing research.

It should be noted that as the hops compounds in your beer degrade, its “immune system” will also be less effective as time goes by. This loss of protective ability is usually only an issue if the integrity of a bottle has been compromised.  If you pull a bottle out of your cellar after a couple of years and it tastes very off (sour, buttery, ect..) chances are some bacteria have snuck in along the way somewhere. You don’t have to worry about them hurting you, but it won’t make for a very nice drinking experience.

Taking all of this info into account, it’s pretty easy to see that beers that rely primarily on hops for their flavor will not be great performers in the cellar. For a hoppy beer to succeed in the cellar, it generally needs to have some other background flavors that can come out and stand on their own as the hop flavors recede. A high ABV% will help as well, since that will encourage the development of new flavors over time. 

If you want to try a hoppy beer in your cellar, Dogfish Head’s 120 min IPA has been known to fare well over time. I haven’t confirmed it for myself, but I will!