How does beer get carbonated?

A close up of a glass of light beer on an outdoor patio table. You can really see the carbonation bubbles. There is fresh-cooked corn on the cob in the background..

Much of what you love most about beer is ultimately thanks to its bubbles. Here’s how carbonation works and why it’s so important

Quick: What’s the most important ingredient in beer? If you answered “yeast,” then you are correct. No offence to malt and hops, of course, but without yeast, your favourite beverage (and ours) would lack two rather crucial components: alcohol and carbonation. And the latter is responsible for a lot more of the good stuff you love about beer than you might think. So, how does beer get carbonated? Let’s find out!

What is carbonation?

What we refer to as “carbonation” is actually tiny bubbles of carbon dioxide (CO2). This fizz is created naturally during the brewing process, but levels are usually further enhanced by the brewer before the beer is ready to drink.

Why is carbonation so important?

Aside from creating the refreshingly zingy mouth feel of most beer styles, those tiny bubbles also play a huge role in how beer smells and tastes. They’re the vehicle that draws those delicious aromas — pine needles! Pineapple! Toasted biscuit! — out of the glass and into your nose. And their work doesn’t end there: Aroma, in turn, influences how beer tastes, too.

Read this article for more on why you should always smell your beer.

How is carbonation measured?

Carbonation is measured in two ways: by volumes and by grams per litre. One volume means one litre of CO2 in one litre of liquid, which equals approximately two grams of CO2 per litre. Carbonation levels vary by beer style, but typically range from two to five volumes — meaning that a litre of beer typically contains between four to 10 grams of CO2 per litre.

Do low-carbonation beers exist?

Some styles of beer have less carbonation than others, which may make them a better pick for people who want to avoid feeling gassed-up after enjoying a pint. Here’s how some of the most popular beer styles rank in terms of carbonation. (Please note: all ranges are approximate.)

  • British ales: between 1.5 and 2.0 volumes
  • Porters and stouts: between 1.7 and 2.3 volumes
  • American lagers: between 2.5 and 2.8 volumes
  • American ales: between 2.2 and 3.0 volumes
  • Belgian ales: between 2.0 and 4.5 volumes
  • German wheat beers: between 2.8 and 5.1 volumes

By comparison, champagne is typically carbonated to somewhere between six and seven volumes, and cola is between 3.5 and four volumes.

How is beer carbonated?

Carbonation is a natural by-product of brewing beer, but additional carbonation is often added after brewing is complete.

Need a refresher on the brewing process? Here’s how the magic happens.

  1. Malt is soaked in hot water to create a substance called “mash.”
  2. Next, the mash is strained, and the resulting sugary liquid is called “wort.”
  3. The wort is then boiled with hops. When the desired flavour is achieved, the mixture is cooled.
  4. Yeast is added to the cooled wort-hops mixture, kicking off the fermentation process.
  5. During fermentation — which can take up to 10 days or more, depending on the beer style — the yeast feasts on the sugars in the wort-hops mixture, creating two by-products: alcohol and carbon dioxide (a.k.a. carbonation).
  6. Finally, the fermented beer is cellared for one to three weeks, allowing optimal flavour to develop. It’s then canned or bottled and shipped directly to retailers, such as The Beer Store.

(Want to know more about how beer is made? Here’s a detailed explainer on the brewing process.)

Is all beer carbonated?

Pretty much! The carbonation level of just-brewed beers is usually around one volume or less, but most brewers bump up this number, either via natural methods or through forced carbonation.

What is natural carbonation?

Natural carbonation is the process of adding an additional bit of yeast and/or sugar to beer right before it’s packaged in cans or in bottles. This addition causes the beer to referment during cellaring — referred to as “can conditioning” or “bottle conditioning” — before it’s ready to be enjoyed. The yeast eats up the small amount of oxygen that remains in a can or a bottle after packaging, leading to several good things. First of all, it creates additional carbonation. Second, it adds another subtle layer of aromatics and flavour. Finally, it enhances shelf life, as lingering oxygen eventually deteriorates a beer’s flavour.

What is forced carbonation?

As the name implies, forced carbonation is the process of directly adding additional CO2 to beer in order to increase carbonation — the same process employed by your countertop soda water maker. It’s an easy way to get beer to its optimal carbonation level, with two drawbacks: You won’t get that additional layer of aromatics and flavour created by conditioning, and it doesn’t prolong shelf life.

What is cask ale?

Cask ale, also called “cask-conditioned ale” or “real ale,” is a form of draught beer that predates kegs. This ale completes its fermentation process in the cask at the pub. Before the cask is tapped, a vent is opened to allow extra gasses to escape, then the beer is pumped manually. (This means that, unlike beer that runs through draught lines, no additional gas is added.)

Cask ale is typically served at a warmer temperature than most other beer styles — usually between 10 C and 14 C, referred to as “cellar temperature” — and is lightly carbonated (approximately one volume). Cask ale remains popular today, and, in addition to ales, barley wines and imperial stouts can also be cask-conditioned.

What is nitro beer?

Nitro beer is any beer that is carbonated with a higher proportion of nitrogen than traditional beer. Brewers use nitrogen to achieve a greater number of tinier bubbles than with CO2. These bubbles create a rich, silky texture and an incredibly creamy head.

Nitro beers were created to mimic the qualities of cask ale, while reducing the types of style inconsistencies that can arise when a beer finishes its fermentation process at the pub, rather than at the brewery.

At first, nitro beers were only available on draught. But, eventually, a nitrogen-filled widget was invented for canned beer, so that people could enjoy the same experience at home. Today, a variety of brewers make nitro beers (typically stouts).

What does it mean when a beer is “on nitro”?

You might notice certain beers listed as “on nitro” at your local pub. Most draught systems use a mix of around 70 per cent CO2 and 30 per cent nitrogen. A beer that’s on nitro is put through a draught system that flips these proportions, using 70 per cent nitrogen and 30 per cent CO2. This type of nitrogen infusion is most commonly done with stouts and porters.

How does beer stay carbonated?

A properly sealed and stored can or bottle of beer will retain its ideal carbonation for at least three months. Remember, it’s always best to store beer upright, in a cool, dark place — whether it’s in your fridge or in your basement. This will help minimize surface contact with the small amount of oxygen that remains in a can or a bottle of beer after packaging.

The best indication that your beer is still well carbonated? That satisfying “hiss” after you crack open the can or the bottle.

Why does beer go flat?

Oxygen is enemy number one when it comes to beer. Over time, it deteriorates flavour and carbonation — a process known as oxidation. Exposure to light and heat accelerates this process (which is why we’re a bit of a broken record when it comes to how to store beer properly at home).

Carbonation also decreases after you’ve opened a beer. Once again, oxygen is to blame here, as is heat. Colder liquids hold on to carbonation better, so as your beer warms up, its carbonation begins to dissipate.

What can I do with flat beer?

Sure, you can still drink it, but the experience will fall a bit…flat. Instead, consider giving your stale beer a second life in one of the creative ways listed in this article: 8 things you won’t believe you can do with beer.

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