How is beer carbonated?
That’s actually a question that has more answers than you might think, and for some beer enthusiasts, it’s serious enough to determine whether they’ll drink a beer or not.
In simple terms, beer is carbonated by adding carbon dioxide to it, to achieve the desired level depending on the format and style. Most ales contain around 4.8g/L (or 2.7 grams per pint) of carbon dioxide.
Lagers or wheat beers generally have more carbonation, while cask beers typically have less. The most common method of carbonating beer is simply by forcing carbon dioxide into it under pressure. The specific process may vary among breweries, but it is usually done when the beer has finished fermenting and is cold (around 0 degrees Celsius). This step is typically the final one before the beer is stored and packaged.
Due to something called Henry’s Law, colder liquids can hold more gas. That’s why a warm can of Coke fizzes more when opened compared to an ice-cold one from the fridge. The warmer coke cannot contain as much gas. Brewers are aware of this law and utilize it, as higher pressure and lower temperature facilitate more efficient gas absorption by the liquid.
Brewers often utilize a device called a ‘carbonation stone’ (mentioned above), which is a small ceramic cylinder through which the gas is bubbled into the beer. The tiny pores in the stone reduce bubble size, allowing for more efficient contact between the gas and the beer. This concept may be familiar to those who own a home aquarium.
ACE beer carbonation stone
Another method involves applying significant pressure to the top of the liquid so that the beer absorbs carbon dioxide through ‘top pressure’. However, this method takes longer, typically a few days compared to a few hours with a carbonation stone.
Larger breweries, as they often do, employ a faster and more expensive method. They use machines that instantly carbonate the beer to precise specifications as it flows rapidly through pipes, heading for packaging. The beer enters the machine without carbonation and exits carbonated.
Anecdotally, this method may result in a rougher mouthfeel, but there is no concrete evidence to support this claim.
However, these methods can upset purists. If you enjoy beer, you’ve likely encountered CAMRA in some form. This group was formed in response to a decline in cask beer consumption during the 1960s and 1970s.
One of CAMRA’s fundamental principles revolves around carbonation. In fact, they only consider beer as ‘real ale’ if it is ‘alive’. In terms of carbonation, this means that the beer is added flat to a cask or bottle and then sugar is added. The package is sealed, allowed to warm up, and the yeast still present in the beer consumes the sugar, converting it into carbon dioxide.
Since this process occurs under pressure in the cask, can, keg, or bottle, the carbon dioxide cannot escape, resulting in carbonation. The presence of live yeast makes the beer ‘alive’, and this particular method of carbonation qualifies it as ‘real ale’. Some breweries opt to add fermenting beer instead of sugar, achieving a similar effect without the need for processed sugar.
Another method, perhaps the rarest, involves deliberately halting fermentation by cooling the beer before the yeast has finished consuming all the sugar. The beer can then be packaged, allowed to warm up again, and the yeast will reactivate, continuing to consume the remaining sugar.
If this is done at precisely the right time during fermentation, the yeast will complete its task, rudely interrupted by the brewer, and the beer will carbonate perfectly in the package.
So, the next time you enjoy a cold beer and feel that tingle on your tongue (or proudly burp in celebration), you can impress others with your knowledge of the carbon dioxide you’re interacting with.
