Episode 099

Understanding Carbonation

To start, let’s look at a curious little molecule called CO2 – you know, the thing that trees breathe.

And you know, CO2 isn’t always a popular molecule, right? We constantly hear ecological reports saying that we need to drastically decrease our global CO2 emissions in order to curb global warming, so there’s that. But when it comes to beverages, CO2 is the molecule most often responsible for activating your trigeminal nerve with its fizzy, tickly little bubbles.

The trigeminal nerve, of course, is the nerve responsible for sensation in the mouth and head. It communicates feelings like spiciness, cooling, and tingling to the brain. And the bubbles in your drink are there because at some point before it got to you, someone dissolved carbon dioxide in your water, producing a compound called H2 – CO3 – AKA, carbonic acid. So if you’ve ever noticed that carbonated water tastes a bit more acidic than normal water – you’re right, and that’s why. Acid.

Now, there’s a reason why carbonated beverages go flat when you leave them open, and that’s because, in order for CO2 to dissolve optimally (and stay dissolved) in water, the liquid has to be really cold (but not frozen), and everything has to be done in a closed system under a great deal of pressure. When you first open your carbonated beverage, the CO2 starts to escape, and as long as your beverage stays reasonably cold and you consume it in a reasonable amount of time, you get the benefit of those nice tingly bubbles to spice things up.

Joesph Priestly and the History of Carbonation

One great story about the history of carbonated water is that in 1767, a British dude named Joseph Priestly decided he was going to suspend a bowl of water above a fermenting batch of beer. And if you know how fermentation works, you know that yeast produce two substances when they eat sugar: alcohol and CO2. So when Joseph Priestly came back to his water and tasted it, he found that it was lightly bubbly, and this, of course, was pleasant to him.

Then he went about optimizing this process using bellows and various air bladders, and he would eventually go on to publish the rapiest sounding scientific paper ever, entitled: Impregnating Water with Fixed Air.

Flavor in Water

Of course, we all like to think about water as essentially flavorless, but that just ain’t the case. The primary culprits that affect water flavor tend to be minerals that are dissolved in that water either due to the mineral composition of the aquifer from which the water is drawn, or due to human intervention – for better or worse.

Lots of people like to fiddle with the chemical makeup of their water for a desired outcome. Starbucks does it with their coffee, brewers and distillers do it with their booze, and there’s even this odd cultural notion that the water in New York city is responsible for the quality of their bagels. I’m still skeptical of that last one (since the water in New York today is radically different than it was when the first bagels were boiled), but I think it’s safe to say that when you drink a glass of water, most of the time you’re consuming more than just pure H2O.

So, knowing that we like to dissolve stuff in our water to make it taste a certain way, let’s talk about the differences between sparkling water, seltzer, and club soda.

Seltzer vs. Club Soda vs. Sparkling Water

All you need to know to be able to understand the difference is whether the carbonation is natural or artificial, and whether or not any mineral flavoring compounds are present, either naturally occurring or through human intervention.

Seltzer

Let’s start with Seltzer, which is the simplest product of the bunch.

It is A.) artificially carbonated using CO2, and B.) contains no added mineral compounds for flavoring. Plain seltzer is just water plus bubbles, which is why so many brands out there choose to use fruit essences to make it more interesting.

Club Soda

Club soda is also artificially carbonated, but unlike seltzer, it contains the addition of a compound called “bicarbonate of soda,” which gives it a specific flavor and sets it apart from seltzer and sparkling water. This is why it’s really nice to use in your highball cocktails because that bicarbonate of soda is actually going to play off of your scotch or other whisky.

Sparkling Water

Finally, we’ve got sparkling water, which is the most magical sounding. And it is kinda magical because unlike the other two, sparkling water is naturally carbonated and bottled at the source, which is usually some sort of artesian well. Spring water has the benefit of added minerals for flavoring, but these are naturally occurring.

As a result of all this, sparkling water tends to be less aggressively effervescent than club soda or seltzer, but each different brand is going to have its own signature flavor due to the geologic mineral makeup of the aquifer from which it was taken.

Of course, this paints a romantic picture of a water that comes to us with its own inherent qualities, completely devoid of human intervention, but the ugly truth is that in most American markets, sparkling water contains some extra carbonation because we like BIG FLAVORS – AND LOTS OF BUBBLES!

Summary

But, that one fact aside, it’s pretty easy to tell these products apart, right?

• Seltzer – no flavor, human carbonated.

• Club Soda – one predominant flavor, human carbonated

• Sparkling water – natural mineral flavor, ideally naturally carbonated

We should also mention tonic water in this conversation – and the reason why we’re only giving it a brief mention is because it deserves its own episode. It’s got a rich history, some interesting ingredients and medicinal properties, and it also contains sweeteners, which puts it outside of the water plus bubbles category we’re playing in.

Topics for Further Investigation

Let’s wrap up this bar cart foundations episode with a few other little tidbits that are adjacent to carbonation in the cocktail world.

Carbonation Via Fermentation

First up, let’s talk about carbonation VIA fermentation, i.e. how beer and sparkling wine get their fizz.

Now, remember Joesph Priestly from earlier in the episode? There’s a reason why he chose to suspend his water above a beer fermenter. Basically, if you can bottle a beverage that’s been fermented before it goes flat, it’s going to have some bubbles in it.

Great examples are Kombucha, which is fermented using a synthetic mixture of yeast and bacteria called SCOBY, and Tepache, which is a Mexican fermented beverage containing pineapple skins, sugar, and spice. It is usually very lightly alcoholic in the tradition of the weak beers that people used to drink in the days before purified water was feasible.

Soda Siphons

Another bubbly topic that’s pretty interesting is that hardware that’s used to make carbonated beverages in the home or at the bar. Of course, we live in the age of the soda stream, which is a counter-top carbonation device with CO2 cartridges that can pump out flavored or unflavored carbonated beverages to your exact specifications. But what I’m most intrigued by is the classic soda siphon, or seltzer bottle.

You may have come across this device in old slapstick comedy or clown routines. It looks like if a fire extinguisher had a baby with a beautiful piece of crystal drinkware. It’s filled at a facility with commercial quality carbonation rigs and then delivered (like milk used to be) to the physical location where it would be used, be it a bar, restaurant, or private residence.

Not only are soda siphons totally cool to look at, and really fun to use, but they are unfortunately, a dying breed – a past commodity that is now an oddity. I’m going to put a link in the show notes for this episode over at ModernBarCart.com/podcast to a fantastic Bon Appetite Video called The Last Seltzer Men, chronicling the Brooklyn Seltzer Boys, the last company in the U.S. to still hand distribute charged, reusable seltzer siphons.

Nitro Beverages

Finally, I wanted to bring up a topic that was suggested by our audio engineer, Sami, and that topic is nitro.

You’ve probably come across this in cold brew coffee and beer most popularly, and basically, it is the addition of nitrogen bubbles, which is very similar to the carbonation process with a few key differences.

The important one is that nitrogen doesn’t like to dissolve like CO2 does. It just hangs out next to the liquid molecules instead of becoming “one with them.” Nitrogen bubbles are also smaller and smoother than CO2 bubbles. These two facts team up to create the rich, creamy mouthfeel of a nitro beverage. Some folks say that this has a noticeable impact of lower perceived bitterness in drinks – but for me, it’s all about that mouthfeel.

To date, there aren’t a ton of bars out there serving nitro cocktails (which are definitely different than simply cocktails on tap). But I think it’s a trend we can probably see following on the heels of the beer and cold brew coffee success stories.