Creating the Perfect Head: How Carbonation Affects Your Beer

When we walk into a bar on a hot summer day and order a cold crisp beer, all those little bubbles that rise from the bottom only to be lost into a head of foam is certainly visually appealing! While admiring all this we take a sip of the beer, we are immediately rejuvenated by the flavour and aroma imparted by a well-carbonated beer. All this is only possible when the beer is adequately carbonated, resulting in a beverage which can be thoroughly enjoyed.

Carbonation is the process by which carbon dioxide is dissolved in a beverage under pressure and at lower temperatures. Carbon dioxide dissolves in beer until it reaches saturation and when we remove the pressure blanket from the bottle/tank or pour it into a glass, carbon dioxide escapes which then result in the bubbles!

In a brewpub, we maintain the beer under a carbon dioxide blanket for two reasons:

1. The first step is to maintain the beer well carbonated at a given pressure depending on the beer style.

2. Since beer is a delicate beverage, we need to avoid its contact with air. Whenever it comes into contact with oxygen, it starts to oxidise and you wouldn't want that in a beer. Oxidation in a beer is generally considered as an off flavour.

We describe a beer based on mouthfeel as having low carbonation, medium carbonation, or high carbonation.

In a brewery, beer can be carbonated in three ways:

1. Natural carbonation : It is my preferred technique of carbonating a beer, at least in a microbrewery. When yeast gets added to wort, it converts sugars into CO2 and alcohol. We trap the Carbon dioxide in the beer, and since it does not have anywhere to go, it dissolves into the beer. The dissolution produces extremely minuscule bubbles that bind to the beer's flavours. A naturally carbonated beer also has excellent head retention! When the temperature is lower, CO2 attains saturation and dissolves quicker in beer.

2. Forced carbonation/Artificial carbonation: As the name implies, this method of carbonation is injected from the outside, either using a “carb stone” (made of porous material to bubble co2 through) or simply by maintaining a blanket of CO2 on top of the beverage. Both the variations have their own way where using a carb stone in beer carbonates the beer faster, whereas a blanket of co2 takes few days to attain saturation. Temperatures would have to be relatively low in both instances. We typically keep it between 0 - 2 degrees Celsius.

3. Shaking the kegs: If the beer on tap is low on carbonation, breweries using kegs could carbonate it by rolling and shaking the kegs in the cool room while slowly adding carbon dioxide. It takes some effort and time, but it works!

There are other times where the beer is overly carbonated, this result in excessive foaming during pouring which results in losses of beer. One method is to release part of the CO2 from the tank or keg and let it sit for a period till the pressure rises, as releasing the pressure from the top causes an imbalance between the dissolved CO2 in the liquid and the top pressure, it will eventually approach the required pressure, providing us with the desired volume of CO2.