If you drink craft beer chances are sooner or later you’re going to hear folks throw around the term ‘bottle conditioning’ or ‘bottle conditioned’. Chances are also pretty good that you haven’t a clue what that means. Well, fret no longer, because today we’re going to look at what it means for your beer.
On the most basic level bottle conditioning refers to how a beer is carbonated. Non-bottle conditioned beer, along with most carbonated liquids such as soda and tonic water are carbonated through a process known as forced carbonation. This involves taking carbon dioxide (CO2) and forcefully pumping it into a sealed container of your liquid of choice. Under the right conditions the CO2 will dissolve into the beer, carbonating it. Once the container is depressurized, for example by popping the cap off a beer bottle, the CO2 rushes out of the beer, giving it that lovely fizzy quality we’ve all come to know and love.
When a beer is said to be bottle-conditioned the process works a bit differently. Instead of artificially carbonating the beer, bottle conditioned beer allows the yeast to naturally carbonate the beer after fermentation is complete. As you’ll recall from our article on how beer is made, fermentation works by having the yeast eat the sugars in the wort and spitting out alcohol and CO2 as waste products. During fermentation the CO2 is allow to bubble off and escape, but once fermentation is complete and the yeast has magically transformed your sugary wort into alcoholic beer, bottle conditioned beer has a little bit of extra yeast or extra sugar or something else added to restart the yeast. Once again the yeast produces alcohol and CO2. Since the beer is now bottled and capped before this happens the CO2 produced by the yeast has nowhere to go and dissolves into the beer, carbonating it.
Because active yeast remains in a bottle-conditioned beer, it continues to develop and age ever so slightly over time. This makes bottle conditioned beer perfect for aging, as it will continue to mature, much like a fine wine. Non-bottle conditioned beer on the other hand has all yeast removed from it before it’s bottled, ensuring the beer will change much slower and providing a higher level of consistency than the bottle conditioned stuff. This gives non-bottle conditioned beer a much shorter shelf life than it’s yeasty cousin.
While certain styles of bottle-conditioned beer benefits from pouring the yeast into your glass, such as hefeweizens, the majority will taste a bit off if the yeast makes it into the glass, so when pouring your beer it’s recommended you take care to avoid pouring the last bit with the yeast into your glass.