For most beers, bottling is the final step in the brewing process. But a technique called bottle-conditioning throws the process a little off-track while adding layers of flavor, mouthfeel and ageability.
When brewers opt to bottle-condition, they add live yeast just before capping or corking a beer and leave it in a warm room for at least two weeks to allow the yeast to work its magic. In the simplest terms, the yeast converts sugar to carbon dioxide and alcohol.
"Bottle-conditioning is that kiss of carbonation done in the bottle, as opposed to carbonating in a tank," says Dogfish Head Quality Control Manager Rebecca Newman.
Each of those beers goes into the bottle with little to no carbonation. Namaste and My Antonia go through suspended fermentation, meaning the yeast goes after the residual sugars in the beer. 75 Minute IPA, on the other hand, is primed.
"With the 75 minute," says Rebecca, "the sugar we use for bottle-conditioning is maple syrup, so it lends a really unique flavor dynamic that's different than all our other beers."
Although bottle-conditioning typically doesn't change alcohol content all that much, it can help a beer age gracefully. The live yeast suppresses oxidation and the breakdown of flavors, potentially adding years to shelf life.
There are two tell-tales to bottle-conditioned beers. One is a lively, champagne-like mouthfeel, and the other is a residue that often settles on the bottom of the bottle.
"A lot of people will pour off the brighter top part of the bottle and then swirl the dregs in and finish the pour," says Rebecca. "Personally, I like the brighter pour. I like what the yeast did, but I don't necessarily want to taste it. It just depends on what kind of flavor and mouthfeel you like."