The Science Behind Beer Carbonation

Glass of foaming beer

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Bubbly beer is such a unique and distinct element of beer. Carbonation gives the beer it's distinct refreshing aspect and contributes to its mouthfeel. 

What Is Carbonation?

In simple terms, carbonation is the carbon dioxide gas in a liquid. To keep the carbon dioxide gas in the liquid, there needs to be pressure. With beer, this pressure is a sealed bottle cap or tab. When the pressure is released, the carbon dioxide rises to escape in the form of bubbles or carbonation.

All beer leaves the brewer carbonated. This is accomplished in one of two ways—natural and forced carbonation. In both cases, beer and carbon dioxide are sealed in a container under pressure. The beer absorbs the carbon dioxide giving the beer its fizz.

What Is Natural Carbonation?

Natural carbonation results from the fermentation process. Fermentation produces alcohol and carbon dioxide as yeast digests the sugar in the wort. Although most of the carbon dioxide is allowed to escape during fermentation, the brewer will seal the beer in a container when it is almost complete. This is how natural carbonation is used to carbonate beer in holding vessels at the brewery and in casks.

Another way to use natural carbonation is in the bottle. In this case, the beer is allowed to ferment completely. It is left unfiltered which leaves active yeast suspended in it. Then a small amount of sugar is added at bottling time. Once the bottles are sealed and the yeast begins to act on the sugar, carbon dioxide is released and absorbed by the beer.

What Is Forced Carbonation?

When beer is force carbonated it is allowed to fully ferment. Then carbon dioxide is pumped into a sealed container with the beer and absorbed into the liquid. It is common to use a forced carbonation method for kegs. Forced carbonation involves pumping carbon dioxide into a keg of beer after it’s been refrigerated. After a few days, the carbon dioxide will be absorbed into the beer and will completely carbonate it. 

Keeping Beer Carbonated

Beer must be fully sealed with a tight bottle cap to maintain the carbonation. A tight bottle cap ensures that no carbon dioxide can escape until the beer is opened. Once a beer is opened, it should be drunk within a few hours. Any longer than that and the beer will taste much different than you expected. The carbonation will be gone (also known as "going flat") and it will not be enjoyable. Most beers with low alcohol by volume (ABV) percentage, can be stored unopened for about 6 months. After that, they risk going flat. Most beers with a higher ABV number are made to age, so leaving them unopened for a few years actually improves their flavor. Beers with higher ABVs that can be aged include lambic or stouts

Storing Beer Correctly

Beers do not like light, so they should be packaged in dark bottles and stored in a cool, dark place away from sunlight. If the beer is in a keg or can these are both impenetrable to sunlight and your beer is safe from bright light.