Beer Fact Friday: Carbonation
We’re nearing the end of our deep dive into the brewing process, folks. We’ve covered eight steps so far: Milling, Mashing, Lautering, Boiling, Whirlpooling, Cooling, Fermentation, and Filtration. At this point in the process, our beer contains alcohol and tastes great, but it’s missing one key element. Time to add some bubbles.
During the fermentation stage, yeast produce carbon dioxide as a byproduct of their sugar digestion. For some beers—British cask ales, primarily—this yeast-derived carbonation is all the brewer will need. More often, however, brewers will allow any gas produced by yeast to escape from the fermentation tank via blowoff tubes submerged in water—you’ll often see these furiously bubbling inside buckets set up near the fermenter.
Once fermentation is complete and the yeast is filtered, the beer is usually transferred to another vessel called a brite tank. Here, carbon dioxide can be added directly to the beer with a “carbonation stone,” a hollow steel rod punctured with thousands of tiny holes. As CO2 is forced through the carbonation stone, the gas enters the beer in the form of miniscule bubbles that dissolve into the liquid as they rise. This practice enables brewers to quickly carbonate a large volume of beer while controlling the level of CO2 in the finished product.
Another method of carbonating beer is by adding sugar and live yeast to uncarbonated beer just before it’s bottled. As the yeast consumes the priming sugar, it gives off carbon dioxide, making the beer inside the bottle sparkling and lively. This method, known as “bottle conditioning,” is common among Belgian brewers and producers of sour and wild ales.
Beer Fact Friday is our weekly exploration of the topics that make beer the world’s most interesting beverage. Check back here next week—or follow us on Facebook, Instagram, or Twitter—for more fascinating beer trivia.