Introduction to Beer Carbonation

Why Getting it Right is so Important

Author: Dan Broaddus

We don't list Carbon Dioxide (CO2) as an ingredient in our beer, but one could argue that we should. The primary reason we don't is that CO2 occurs in beer as a natural by-product of the brewing process. The reason that some of us feel it should be included, however, is because modern brewing, kegging, and packaging methods cause carbonation loss.

The lost CO2 is forcibly reintroduced during the finishing process of the beer. If the beer is served from a keg, CO2 is introduced again, during dispense. Finally, in the case of nitrogenous beers such as Guinness, Boddington's, Old Speckled Hen, and numerous others, we also add nitrogen gas as way to lighten the mouth feel of these low carbonation brews.

The reason I would advocate for listing gasses as ingredients is to show customers that only 1 or 2 gasses are supposed to be there, lending credibility to quality advocates. These gasses affect both flavour and presentation. When the additions of gasses—which are not part of the recipe—cause issues, it will help both brewers and quality advocates, such as good Technicians and Cicerone's, bolster our cause. We can say, "The beer is not the issue, your crappy gas mix, or air blend, is the issue."

For those of you not yet versed in the Beer and CO2 relationship, there are a few things we need to touch on.

Measuring C02 Content

There are several measurements of CO2 content, but the one most widely used in North America, especially when it comes to keg beer, is "Volumes of CO2."

Maintaining C02 Content

At Temperature and Under Pressure

CO2 does not want to stay in solution. At least, not in the amounts we want in our beers. We manage to keep it there by keeping it confined, under pressure, and cold. And by cold, I mean below 4°c/40°f. The temps at which many of us enjoy our ales are in fact too warm for successful dispense.

C02 Replacement

As we remove beer from a keg, we must replace it with pressurized gas, or some of the CO2 will come out of solution and the beer will taste "flat."

Ensuring Proper Flavour

Remember that CO2 is a HUGE part of beer flavour. The popping bubbles increase aroma. Sense of smell accounts for about half of the flavour experience. If you don't believe me, the next time you have a beer, pinch your nose, and take a sip.

CO2 also adds a sharp, vaguely smoky, bitterness. As the bubbles bloom on your tongue, they serve to balance the richest and sweetest notes, which might otherwise overwhelm the beer’s flavour profile. Think about how much sweeter a soda seems when it goes flat. Think about how carbonated water tastes vs. still water, and how, even if after it goes flat, the flavour lingers. The right amount of CO2 is needed to balance a beer's flavour correctly.

Balance, Balance, Balance

Ensuring Proper Pressure

Sometimes, the correct pressure for maintaining carbonation is all that is required to dispense the beer. Such beer systems are usually very short, most commonly serving right through the cooler wall: AKA Direct Draw.</p>

Most systems, however, require more pressure to keep the beer in solution as it travels toward the faucet. Mechanical Pumps, or blends of gasses, are used to provide this extra boost. If one simply turns up the CO2 it will over-carbonate the beer, be difficult to pour, taste sharp, and bloat the consumer. A bloated customer won’t order a second beer, appetizers, a dessert… and worst of all is less likely to go home with cans or a Growler.

Foreign Gasses

Nitrogen Additions & Blended Gasses

Often, the method used to augment pressure is blended gas, most commonly nitrogen (N2). At the lower pressures required for non-nitrogenous beers, nitrogen will not, to any great degree, go into solution. What little that may will boil out upon dispense, with infinitesimal effect on flavour.

Nitrogen's inert characteristics further safeguard the beer’s chemistry, which to this point, serves in keeping active yeast and bacterium dormant. This blend is commonly created on site with a blender that is fed by compressed gas cylinders, or by a nitrogen harvester/generator. Beer pumps are usually driven by gas or compressed air. This air is clean and dry, and never touches the beer. If need be, electric pumps are also available.

Compressed Air Ruins Beer

In days past, and even today on rare and sorrowful occasions, people use compressed air mixes, to provide the extra pressure. This ruins the beer. Oxygen is horrific for your beer!

The helpful yeast and bacteria that created your beer are, at this point, either dead and preserved, or comatose. Oxygenation causes the comatose ones wake up… and start brewing again. At this point, since yeast are weaker and fewer, they begin to lose dominance. They are overtaken by oxidizing bacteria.

Oxygenation Leads to Bacterial Growth

WARNING: NOT FOR THE QUEASY. If you have a weak stomach, trust that air and oxygen are bad for beer, and move on to Nitrogenous beers.

Air is the friend of oxygenating agents such as Lactobacillus acidophilus, and any of the 10 genera from the Acetobacteraceae family of Bacteria. Pediococcus and maybe even Megasphaera, like Clostridium (less common in beer, but the one that will cause food poisoning) or Pectinatus are likely present, as well.

These Bacteria create diacetyl lactic acids (butterscotch,) acetic acid (vinegar,) butyric acid (bile,) methane, and hydrogen sulfide (swamp/sewer gas.) The smells produced are as if someone were pickling eggs in a busy, 3rd-world brothel. The flavour addition, for me, is a cross between eggnog and over-cooked, hard-boiled egg, with a bit of preserved lemon and butter in the finish, all the while, vaguely whiffing of vomit.

Nitrogenous Beers

Not all Nitro Beers are Stouts!

This family of beers are commonly referred to as stouts, but this is not really correct. While many nitro beers are stout ales, some are not. Two popular examples are Boddington's and Old Speckled Hen. Furthermore, not all Stout Ales are Nitrogenous. Guinness makes a non-nitrogenous Extra-Stout, which is about 2.5 volumes, to my recollection. "Nitros" are generally ales, but nitro lagers have begun to make an appearance.

Nitrogen Balances Low C02 Content

One common characteristic of nitros is that they are lower in CO2 content. They are also usually malty, nutty, chocolaty, and/or seem heavier on the bitters. Even though they are often lighter in sugars, they are unfairly accused of being "heavy," as the reduced CO2 content makes for a denser mouth feel.

This is where nitrogen saves they day! The fine bubbles in the solution serve to lighten the mouth feel and draw out the sweeter and creamier notes, serving to offset and balance the bitters. If carbonated at the level of a regular ale or lager, the bitterness would be too intense for most drinkers.

These beers are designed for, and finished with, Nitrogen, and are crippled without it. Whenever possible, blend the gas on-site by Blender box, generator/blender, or in a cylinder equipped with a self-mixing valve.

Responsiblity, Ownership, and Ambassadorship

Responsibility

As an Equipment Technician and System Designer, my first responsibility is to the beer. I identify with Lord Varys from Game of Thrones, who answered the inquiry as to who he serves by saying: "I serve The Realm. Somebody ought to." Well, I act in service to the beer. We all ought to. To be more specific, I do my utmost to ensure that the beer in your glass meets the expectation of the brewer's intention. All of my choices are made to protect the beer, first.

My second responsibility is to practical operation and maintenance, over the 5-15 year life of the assorted components. My 3rd desire is to blend with, pay homage to, or enhance the aesthetic and culture of the location. Just remember, when it comes to front of house aesthetic, the most attractive, valuable thing you can put in view of potential customers is a smiling and happy patron who wants you to succeed. A pretty beer tower is a nice to have, not a need to have.

Taking Ownership

Remember that if you touch it, or can't prove you didn't, it belongs to you. Leave everything better than you found it. If there is a dangerous situation, you really should insist it be corrected. If the owner refuses, document it, and report it.

If somebody is injured or killed by something that you could have corrected or reported, I don't imagine it's going to sit well with you. Even if you or your employer are unmoved by concern for your fellow humans, there are still possible financial and criminal prosecutions that may result from an investigation. Keep good records, takes pictures, and report dangerous situations to the appropriate authorities.

Ambassadorship

Confession: I don't care for sours, and it isn't often that I find a lager or pilsner that I actually enjoy. Then again, I do enjoy some paint peeling porters, and some multi-layered Belgian ales that many would wrinkle their nose at. I also enjoy a radler or a shandy. There! I've said it. Can we just move on, please?

What I really want to illustrate, is that what makes a beer "good" is subjective. To each their own. Just because I don't care for it, doesn't mean it's bad. It only means that it is not to my taste.

Our community is smaller than it seems. It’s also a community full of people who are, for the most part, kind and generous. It is very easy to make friends. It is also pretty easy to gain a reputation as an asshole. And once you have managed to earn such a reputation, amongst such a kind and accepting community, it is awfully hard to change that perception. In this industry, if you take care of everything you touch, people will take notice… and in turn, they will take care of you.

I'm going to paraphrase one of my favorite authors, Robert A Heinlein:

"Moving parts, in rubbing contact, require lubrication to prevent wear. Formal politeness, honorifics, and manners serve to provide lubrication where society rubs together. Unfortunately, there are often entitled, ignorant, often poorly read, or untraveled people who ignore the most basic manners. They bypass and dismiss any politeness or honorific, formal or otherwise, espousing them as empty, meaningless, beneath them, or a waste of time. In actuality, this disregard is hurling sand into a machinery, which doesn't work too well to begin with."*

So now, with this basic understanding of beer gas, and this roadmap to enlightenment before you, go forth. I send you off with the words which saw my child to school, in the Before Times: Be safe. Be kind. Have fun.

Cheers,

Dan Broaddus
Technical Advisor
Canadian Beverage Supply & Chill-Max Beverage Solutions

*Paraphrased from Time Enough for Love and The Notebooks of Lazurus Long. By Robert A. Heinlein.