After writing about nucleation points, I began pondering carbonation as a whole. Typically we laud water, barley, hops, and yeast as stars of the show while CO2 remains a silent partner – why is that?
What would beer be without carbonation – those tiny bubbles of joy dancing on our palates?
Although it would be more similar to the beer of old (before high pressure-holding vessels like glass and metal kegs), un-carbonated beer would likely lose its mainstream luster in today’s world. Carbonation has a thankless, yet crucial job – doing all of the following and more:
- Brightening the beverage
- Lifting aromas to your olfactory system
- Scrubbing your palate
- Creating a sensational mouthfeel
Since it’s clear that CO2 is an important supporting actor, what are the basics of its production in beer? Here’s a three-sentence crash course:
At its core, brewing involves making wort (sugary grain water) which is then dosed with yeast. Since yeast loves to eat sugar, it proceeds to go on a feeding frenzy (i.e. fermentation). The two primary byproducts of that wort fermentation are ethanol (alcohol) and CO2 (which is typically vented via airlock).
With those basics in mind, what are the three most common techniques for carbonating beer?
1) Spunding
Literally translating from German to mean “bunging”, spunding is the process of closing off the fermentation tank after a vigorous primary fermentation takes place. By sealing the tank, additional CO2 produced by fermentation is contained and (if planned correctly) will carbonate the beer to the desired level.
Two elements make this method particularly attractive:
- Natural Process: This method harnesses the natural power of fermentation to carbonate the beverage. Not only is it less wasteful, but it’s also less costly in terms of materials needed.
- Mouthfeel: Carbonation created by this method has been described as creamier and smoother than force carbonation (see below). In the end, this could be more or less appealing depending on who you are, but the unique textural element is another reason to consider this method.
When it comes to the downsides, the biggest risk of spunding is the lack of control. The reason beer is vented during fermentation is due to the necessary release of certain compounds produced. If any of those compounds remain (e.g. DMS, Hydrogen Sulfide, etc.), they can lend to unwanted off-flavors in the final product. Because of this, it’s crucial to not start the spunding process too early or you’ll risk poorly-tasting beer.
2) Bottle/Cask Conditioning
If you’ve dabbled in homebrewing or live in Great Britain, you’re probably familiar with bottle or cask (a type of barrel) conditioning. Where spunding involves closing off a tank during active fermentation, conditioning typically involves stimulating a secondary fermentation in a bottle or cask.
In the case of bottles, this is typically done by adding a small amount of sugar (simple syrup, molasses, honey, etc.) and sometimes yeast prior to filling. Once bottled, the remaining yeast scavenges that sugar and converts it to CO2! Similar to spunding, conditioning is a natural process of carbonating your beer.
In the case of casks, it’s a similar process to bottle conditioning with the exception of being in a barrel and having more control. With bottles, once they’re sealed, your work is done. With casks, cellarmen/publicans carefully manage carbonation through the use of spiles, allowing them to vent or seal off the casks at the proper times. Casks are not always dosed with additional sugar; however, it’s a technique that can be used to reach the desired level of carbonation.
Cask-conditioned ale (or “real ale”) is a celebrated form of beer recognized especially in Great Britain. In fact, an organization (CAMRA) was founded to protect the existence and quality of real ale across Europe.
If you haven’t experienced cask ale before, you’re in for a treat!
3) Force Carbonation
Now that we’ve looked at two (almost magical) ways to carbonate beer, let’s shift our focus to the workhorse of the modern age – force carbonation. As its name suggests, force carbonation involves adding CO2 to flat beer. This can be done in a number of ways, but the most common is through the use of a carbonation stone – a device used to diffuse CO2 into beer. They can “be made of naturally porous stone, porous ceramic, or finely sintered stainless steel.”
The core advantages of this method are as follows:
- Speed: Carbonation can be completed in a matter of hours or even less in the case of in-line carbonation.
- Control: Force carbonation allows for precise control over volumes of CO2 present in a beer. Where spunding and conditioning are less precise, force carbonation allows for replication that many breweries desire – especially at a large scale.
If you’re reading this at your local brewery, it’s likely the beer you’re drinking is force carbonated. It’s a less historic and whimsical method, but it does its job wonderfully.
Final thoughts
Isn’t it crazy how trapping gas inside a liquid can create such a dynamic effect? Although CO2 doesn’t get the same attention as the core four ingredients, it tirelessly lifts aroma to our noses, scrubs our palates, and adds dimension and texture to our drinking experience.
Cheers to you, CO2!