Carbonation of Beer

All beers have carbonation to some extent, whether it be a bubbly, often gassy, lager, or a smooth but still slightly fizzy ale or stout. Where some beers differ is whether the carbonation is a natural process or forced.

Let’s take a look at what carbonation is, how it occurs, and the different methods to carbonate beer.

What is Carbonation?

Put very simply, carbonation is the carbon dioxide gas in a liquid. To make sure the liquid keeps the carbon dioxide inside, there needs to be pressure.

With beer bottles, an air-tight lid helps keep the gas inside. Sealed kegs of beer or casks can also do the same job, although kegs may often use an external source of CO2 to keep the beer under pressure once it is being served.

Once the pressure is released, either by removing the cap of the glass bottle, pulling the ring pull of an aluminum beverage can or tapping a cask, the excess carbon dioxide rises in the form of bubbles or carbonation. It’s what contributes to the distinctive mouthfeel of a beer and many argue adds to the aroma and taste of the beer.

All beers normally leave the production stage carbonated – it would be a pretty bad deal if you received a batch of beer that was flat and lifeless.

The carbonation of beer can be achieved by two methods – natural or forced carbonation. Both techniques seal beer and CO2 in a container which allows the beer to absorb the CO2 over a period of time and gives the beer that fizz.

What is Natural Carbonation?

Natural carbonation is a completely natural process that results from the fermentation stage of brewing beers. As the yeast in a brew digests the fermentable sugars in the wort alcohol and carbon dioxide are produced.

Although most of the carbon dioxide will escape during the primary fermentation process, a brewer has two options to keep the carbon dioxide in the beer.

The first option is to seal the beer in a container when the fermentation is almost complete whereby leftover yeast and additional sugars will continue to produce CO2. This method is most commonly used to carbonate beer in the holding vessels at a brewery or the casks.

The second option is to allow the first fermentation stage to completely finish, then add some additional sugars (known as priming sugar) to the beer after fermentation. This will use any residual yeast in a secondary fermentation inside the sealed vessel.

The beer is then put into secondary sealed containers like beer bottles, growlers, or kegs where the leftover yeast will produce more alcohol and CO2. Because the container is sealed the CO2 will dissolve into the liquid and therefore carbonate the beer.

Adding sugar or secondary yeast is also a method used by many craft beer producers when creating bottle-conditioned beers.

Advantages of natural carbonation include:

• Many beer enthusiasts argue natural carbonation gives a thicker head to the beer with smaller bubbles and more lacing (the ring of foam around the glass as the head dissipates) which is considered more desirable.

• Natural carbonation requires less equipment (which can be costly) than force carbonating. Homebrewers tend to prefer the natural carbonation method for this reason.

• It’s more traditional and all-natural. Some experts argue that force adding CO2 to a beer can result in much carbonic acid which can affect the flavor and aroma of the finished beer.

The disadvantages of natural carbonation include:

• It takes much longer to carbonate the beer. Beer that has been carbonated naturally will need a rest time or additional 2-4 weeks for fermentation and conditioning to occur.

• A constant temperature needs to be maintained to avoid yeast flavors occurring when the yeast has to work too hard during secondary fermentation.

• Care has to be taken on how much extra sugar is added. Too much sugar can lead to the beer being over carbonated or beer in bottles will often explode. Most homebrewers have had this happen to them at some time or another, especially when first starting out.

• It’s possible more yeast will settle at the bottom of the bottle which doesn’t always look too pretty. Although brewers yeast is pretty harmless to most beer drinkers it can still be off-putting to some consumers, especially those with yeast intolerance.

What is Forced Carbonation?

Forced carbonation is when beer is allowed to fully ferment before being transferred to a sealed container which is then refrigerated.

CO2 is then pumped into the sealed container, most commonly a keg, until the desired level of carbonation is reached. Over a period of a few days, the carbon dioxide will be absorbed into the beer and carbonate it.

Although many larger scale brewers use this technique to carbonate beers, Sour beers or many of the Euro styles of beer can pick up some off flavors from the carbonic acid reaction in the beer due to the specialized yeasts used.

Advantages of Forced Carbonation include:

• It’s a much quicker and more efficient carbonation process taking only 3-7 days on average.

• The finished beer looks “cleaner”.

• No more guesswork on how much priming sugar to add.

• No residual yeast flavors or sediment are leftover. A filtered beer can be force carbonated so the beer is completely yeast free.

Disadvantages of Force Carbonation include:

• Expensive equipment is required.

• The head of force carbonated beer can be less billowy and has a worse lacing effect – i.e. it dissipates very quickly and has larger looser bubbles

• Not a natural process and some beer snobs argue it adds off flavors to the beer.