Carbon dioxide is a natural byproduct of fermentation.
As yeast consumes glucose sugars in the wort, it produces both carbon dioxide and alcohol; the process of making beer boils down to a simple chemical reaction.
Other than flavor, the alcohol content is, of course, what we greatly desire in a beer. Natural carbon dioxide from fermentation adds subtle carbonation, but not at the levels you’ll experience from a draft pour or in a bottle after it has been force carbonated.
It might be a challenge to think of it in this way, but gases actually dissolve into fluids, and we call that dissolution.
Henry’s Law (named after a British chemist named William Henry) states that the amount of gas dissolved into a liquid is directly proportional to the amount of partial pressure of that same gas applied on the liquid. That’s why both beer and soda, liquids that generally have plenty of carbon dioxide dissolved inside, go flat when they aren’t consumed in a reasonable time or if the lid is not tightly capped. Without the pressure applied in the headspace of the bottle, the carbon dioxide escapes.
Another factor that affects gases in a liquid is temperature: the colder a beer is, the more gas that can be dissolved in it.
Have you ever left a glass of water out on the counter overnight and noticed tiny bubbles clinging to the inside of the glass in the morning? What you witnessed was the gases releasing themselves from the solution as the liquid warmed, ready to flee to the surface. When you open a beer and pour it into a glass, the carbonation bubbles you visually see and physically feel on taking a sip are those gases slowly warming and, with no more pressure to keep them contained, escaping from the solution.
There’s another type of gas that’s sometimes used in beer instead of carbon dioxide — nitrogen.
About 78 percent of our atmosphere is nitrogen, an important building block of plant and animal life.
Nitrogen isn’t a naturally occurring byproduct of fermentation and its addition to beer had its beginnings with a mathematician, not a brewer.
Hired by Guinness
Michael Ash was hired by Guinness in the early 1950s, along with other brilliant scientists in their respective fields, to help breathe new and innovative life into the brand.
It was Ash who came up with the idea of adding nitrogen to kegs of beer to solve a problem the pubs had at the time, a required mixing of high cask ales (fresher and carrying more naturally-produced carbon dioxide) and low cask ales (older and flatter). The blending and pouring was time consuming and inefficient.
Ash believed nitrogen was the answer.
What does nitrogen do for beer?
For starters, nitrogen doesn’t dissolve into beer as readily as carbon dioxide. This, along with the gas bubbles being tinier, is what provides nitrogen-added beers with a creamy and velvety feeling in the mouth. It also influences how we perceive the flavor of the beer because carbon dioxide bubbles trigger a slightly acidic sensation, thanks to another chemical reaction between the carbon dioxide and water.
As mentioned, nitrogen doesn’t dissolve into liquid quite as well, so drafts are typically poured through a restrictor plate that has tiny holes, encouraging a foamy head. Bottling nitrogen beers presents a whole other challenge: how to make nitrogen foam up when it’s not poured through a tiny-holed restrictor plate.
One answer is a type of widget that Guinness has called a “draft can ball” that releases nitrogen when the can tab is pulled. These small plastic pieces have a hole or a few holes drilled into them and a bit of liquid nitrogen is added to the beer; when it is opened and poured, the widget creates agitation between the beer and the nitrogen and thus a head is formed.
Other methods of enabling the nitrogen to do its thing in a bottled or canned beer exist, but they often are proprietary or held as a guarded secret.
Red velvet cake in a nitro bottle
Ballast Point Brewing Co. released in January its Nitro Red Velvet, a golden oatmeal stout brewed with red beets and chocolate, the first nitrogen-powered bottled beer in its lineup.
Nitro Red Velvet pours a jewellike ruby red from the bottle with a pink-tinged head. After my “pour with a purpose,” as instructed on the bottle, a creamy cloud of dense, strawberry Yoo-Hoo-colored milkiness rapidly settled downward before dissipating entirely into a hazy body with wandering particulates. The head persisted with a dense foaminess throughout the session.
In aroma, I detected oats, chocolate, sweet butter cream, raspberry, light roast and vanilla.
The flavor offered significant bitterness to cut through beet sweetness; there was light roast, semi-sweet chocolate, slight earthiness, vanilla and cake batter. Although the body started somewhat rich, it ended disappointingly thin and watery.
Overall impression: This is a unique beer and I appreciate the idea and innovation behind its creation. That said, it wasn’t nearly as velvety and creamy as stouts poured on nitro at a bar (or what you’ll find when poured from a bottle of Guinness); in fact, it had the mouthfeel of just being mostly flat. The flavor was decent and maybe if you’re a huge fan of red velvet cake, this will appeal to you.
As an aside, the label art on Nitro Red Velvet is a feast for the eyes.
Contact Amber DeGrace with comments and questions at email@example.com and find her on Twitter and Instagram at @amberdegrace.