Why is beer fizzy/carbonated?

Why is beer fizzy/carbonated?

That fizz or carbonation can vary from beer to beer, and can also be the maker or breaker of a beers enjoyment. The gas itself is called Carbon Dioxide or Co2, but when dissolved in liquid you refer to this as carbonic acid. This little change in name already reveals one of the reasons why this gas can be essential to a beer.


There are a few different methods for carbonating beer, but one element that is kept the same is that all containers will be either a keg, cask, can, or bottle. The beer will then be sealed within to keep the Co2 locked inside. The big difference is that some are naturally carbonated, and most are force carbonated.



Natural Carbonation

The reason why this is natural is that when certain ingredients for beer interact (yeast and sugar) they produce carbon dioxide. During primary fermentation in the brewery most of the Co2 escapes, but then the brewer can seal the beer in a container when fermentation is nearly complete. This way some of the Co2 is absorbed into the beer to give a light level of carbonation. This is one form of natural carbonation.


The other comes from secondary fermentation in the bottle, can or cask. Here the Co2 created by the beer in the cask or bottle, is absorbed back into the liquid. Again the container must become pressurised so a decent amount of Co2 must be created.


Visibly, naturally created Co2 is smaller and rounder meaning that the foam/head created on top of the beer can be thicker and last longer. It is also softer on the palette, therefore affecting aroma, taste and mouthfeel. More about this later.



Forced Carbonation

When we say forced, we mean it. The beer is sealed into a container, the container is pumped full of Co2, and after a few days the Co2 is absorbed into the liquid to the brewers desired levels. This is how the majority of beer around the world is carbonated. Then, they are served from pressurised kegs within cellars, bars and festivals across the world.


What about the shape of forced Co2? Well, this form of Co2 is actually a little bigger and is slightly misshapen. This is part of the reason why forced keg products often cannot develop such a thick, creamy head on top of a beer. Or at least not one that lasts!


GEEK OUT: “According to Henry’s Law, “at a constant temperature, the amount of a given gas dissolved in a given type and volume of liquid is directly proportional to the partial pressure of the gas in equilibrium with that liquid”.”[1]


Carbonation and Flavour

So, believe it or not Co2 can really affect each individual’s enjoyment of beer. Some find the forced Co2 very sharp or harsh on their palette. Others find it incredibly refreshing. Some swear that natural Co2 beers lead to more aroma and taste. Others find it incredibly flat and dull. So, who is right?


We are afraid that this article says - all of you! Here’s why…


All individuals taste receptors are different. Carbonic acid is by nature sour, but your beer doesn’t often taste sour, right. What is happening is your tongue is meeting this slight sourness causing your mouth to release more saliva. By releasing more saliva, your palette is watering down the aromas and other tastes. Depending on the nature of the Co2, and the quantity, this can enhance the beer or neutralise it.


That’s an odd word to use: “neutralise”. Yes, I know but I refer to the PH of your mouth being very neutral, and therefore the beer being fairly neutral as well (also, felt nicer than saying bland).


So, your enjoyment of a beer might be related to something as simple as whether the Co2 is balanced correctly. And, whilst that might be a ridiculous statement, we ask that you do a test at home. From the same bottle of beer, pour half the liquid gently into one glass. Then, pour the other half from a much greater height (careful not to miss the glass or splash).


Now, taste the two liquids. You should find the softly poured liquid tastes like the beer you know. The second glass however has changed. Lots of the Co2 has been forced out just by pouring from a decent height (also known as a hard pour). Without the balancing carbonic acid in the beer its flavour is off balance, and doesn’t taste the same. The mouthfeel is also very different.

So, now we have discussed why is beer carbonated. And the reason is – it improves the overall consumer enjoyment, whilst also giving great variety to the third most drunk liquid in the world (water, tea, then beer).

Last question, if carbonation can be so great for enjoyment and variety, why are the majority of wines not carbonated? Well, this is Beer Dad. If Wine Dad ever opens up you should ask them.

Now someone please pass me my tankard of Czech Pilsner on this most awesome of days!


[1] The Oxford Companion to Beer: edited by Garrett Oliver, Steve Parkes, Carbonation; p221

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