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Foam on Beer: Facts about the Fizz

One of the things that makes beer unique from other alcoholic beverages is the effervescent fizzy sensation of abundant carbonation. Without those baby bubbles your beer would come off as lifeless and boring. You may know that all beer contains carbonation, but if you want to know how it gets there and just how important it is, read on.

Carbonation itself is simply carbon dioxide gas (CO2) that’s trapped in a liquid (in this case, beer!). CO2 is highly soluble in water-based liquids and will stay dormant under pressure and at cooler temperatures (this is why a warm beer goes flat faster). When the CO2 is released from beer, it leaves its state of suspension and shows itself in the form of millions of tiny bubbles that carry the wonderful aromas from your beer to your nose and collect at the top of your glass, forming a protective layer of frothy, foamy goodness called head. Beer is the only carbonated alcoholic beverage that creates quite this foamy effect, and it’s due to the type of proteins found in beer from the use of barley malt and adjunct grains, such as wheat.

Carbonation forms as a natural byproduct of fermentation. As yeast digests the sugars found in wort, it converts them to ethanol alcohol and CO2. During the fermentation process, however, brewers will allow the majority of the CO2 produced to vent out from the tanks, which results in beer that would be considered flat without additional help. To raise the CO2 content to more desirable levels, there are two basic methods that brewers use: natural or forced carbonating.

For natural carbonating, brewers transfer the beer to a conditioning tank before fermentation is fully complete. This tank will remain sealed, allowing the CO2 pressure levels to rise instead of venting out as when in a fermenter tank.

Another form of natural carbonating is bottle or keg conditioning. In this technique, brewers allow a select amount of yeast to remain in the beer after fermentation and will add a small dose of sugar during packaging. This allows the remaining yeast to reactivate and convert the added sugar into more CO2. A benefit to this technique is a beer that can often provide an extended shelf life and can continue to develop while aging. But the downside is that the beer will need more time to condition in the bottle (sometimes up to a month) before it can be served and will need to remain at stable temperatures in order to keep the yeast happy. These variables can potentially result in fluctuating levels of CO2.

The other technique, forced carbonating, is the most commonly used practice with commercial brewers, including Hop Valley. In this case the beer is transferred to the conditioning tank after fermentation in complete. Like soda, CO2 is then added to the beer through a diffusion stone and held at select levels until the beer absorbs the desired amount. This technique takes less time than bottle conditioning and can be calibrated to a perfect consistency every time.

Not all beer styles are carbonated equally. Commercial brewers determine the carbonation levels of beer in terms of volumes of CO2. Citrus Mistress, for example, has 2.5 volumes of CO2, and Light Me Up has 2.7. This means there are 2.5 to 2.7 parts CO2 for every one part liquid, respectively. Cask beers, on the other hand, feature a much lower level of carbonation at around 1 to 1.5 volumes, and Belgian styles showcase a very high level of carbonation coming in between 3 and 4.5 volumes of CO2. These varying levels of carbonation also play a part in how bartenders determine the proper pour for particular beer styles and what type of glassware is best.

Part of providing a perfect pour comes from ensuring the proper amount of carbonation is released from the beer prior to consumption. A proper pour helps ensure that the beer’s aromas, flavors, and drinkability are at their peak. A good indicator of this is simply checking the head of the beer in your glass. For most styles of beer, about a half-inch to one-inch of foam will do. If a beer is over-poured, too much carbonation is released and there will be mostly foam in the glass. The result is a flat-tasting beer that’s not as crisp and refreshing. If your beer is under-poured, not enough carbonation is released and there will be little to no head on your beer. This means the carbonation remains trapped inside the liquid. When this happens, aromas and flavors will come off as muted and the carbonation will now be released in your stomach instead of in your glass, filling you up quicker, making it harder to keep drinking and eating and resulting in the famous beer burps. This is also a reason why you should always pour your beer into a glass.

Carbonation serves another crucial function for beer-lovers: carrying the aromas of your beer to your nose and mouth. This is very important due to the fact that around three-fourths of your flavor experience in tasting comes from aroma. If you ever want to test this fact, try eating a cinnamon candy while plugging your nose. Without access to your orthonasal (inhale) and retronasal (exhale) senses, the cinnamon candy will not taste much like cinnamon at all. But once you unplug your nose, you will quickly be consumed by the intense aromatics of the cinnamon, filling out your tasting experience. For beer, it’s much the same and vital portions of the flavor you experience in taste are coming from hop, malt and yeast aromas. Without the aromatic benefits being carried by carbonation, you would be missing out on a lot of these flavorful components. Another reason to always pour your beer in a glass, people!

Carbonation also plays a role in pairing food with beer and is one of the big reasons that beer has the edge in a number of food pairings versus wine. Carbonation in beer is often referred to as “tiny scrubbing bubbles,” since carbonation has the power to scrub and cleanse the pallet preparing you for the next bite, especially with rich and fatty foods, which tend to stick around on your tongue.

So, now maybe you can agree, the effervescent qualities of carbonation in beer are a big part of what makes this beverage so unique and desirable. It’s as important a factor as any hop, malt or yeast, and, without this fifth element, beer would not be the enjoyed and sought-after treat that it is today.