If you haven’t read the first part of this article, be sure to check out Bottle Conditioning (Part 1)

Yeast in bottle-fermented brews can affect your beer in a myriad of different ways. Since the yeast are initially metabolicly active, munching away on sugars in your beer, they can continue producing flavorful compounds well after bottling. It should be noted that the impact on a beer’s overall flavor from these new compounds is thought to be fairly minimal. The real impact on flavor from these yeast suprisingly doesn’t come until after the yeast die off and their bodies start to decompose (usually after a year or so). This process of decomposing yeast is called autolysis, and it can have dramatic effects on the taste of your beer, both good and bad.

As the deceased yeast undergo autolysis, their bodies start to release enzymes and yeasty flavors into beer. These yeasty flavors can be pleasant in small quantities, adding some additional complexity to a brew.  In larger quantities however, they can quickly overwhelm a brew. These off-flavors from autolysis can come across as fruity, apple or cider-like, solvent, bready, buttery, or even grassy. One reason some brewers filter their beer and then add fresh yeast back in is so they can better control the quantity of yeast in their final product, so the beer’s flavor won’t be ravaged by yeast autolysis.

Another thing to realize is that yeast undergoing autolysis are also releasing amino acids into the bottle environment. Because of this increase in amino acids, maillard reactions can start to become much more frequent. This type of reaction can further influence the color and flavor of your beer. Be sure to check out my past article about maillard reactions in beer!

So with this new info about bottle conditioning, we can start to consider some guidelines when cellaring bottle-conditioned beers. First of all, while the yeast are still alive in your brew, you should be even more careful then normal in protecting your beers from sudden changes in temperature. Yeast do not fare well to sudden temperature changes, and you may be sending them to a premature death if you expose them to this kind of environment. If you do kill your yeast off at once, you won’t gain the benefit of the oxygen scavenging while at the same time speeding up the onset of autolysis. This is definitely not a good thing.

You should also pay close attention to these yeasty beers in your cellar. If the yeasty flavors are starting to get strong in a particular beer, it’s going to be a sign that flavors from autolysis are taking over. Refrigeration will help slow things down some, but you’re probably going to want to consume those beers quickly before they slip away.

That’s all for now. Thanks for coming by!

Jason

jason@brewbasement.com