How Water Freezes
A Couple of Cocktails

Carbonation Science

I was lucky enough to get a sample of the Perlini cocktail carbonating system, but before I even got around to using it I was fascinated by carbonation information the instruction manual. 

Note: Yes, I read the instruction manuals.  Pretty much always. 

Perlini shaker

The Perlini is basically a cocktail shaker than you fill with carbon dioxide (CO2), then shake and pour. The manual comes with tips both for using the shaker, and also about carbonation in general. 

So here are some things I learned:

- The amount of CO2 that will go into solution is controlled by pressure and temperature. The higher the pressure, the more CO2 fits. Obviously when you release the pressure (such as opening a bottle of a carbonated beverage) the pressure equalizes and the carbon dioxide comes out of solution.

- The colder the temperature of the liquid, the more CO2 can go into solution. Thus in the case of the Perlini, you add ice to the cocktail shaker. You can also chill the liquids in advance and not use ice (though the shaker is optimized for ice). 

- To keep the carbon dioxide in solution, we want to minimize the amount of bubbles that form and carry CO2 out of solution. Bubbles form when microscopic pockets of gas are found in imperfections in a piece of glassware (note that in a champagne flute most bubbles form a stream from  certain points at the bottom and sides of the glass) or in debris (solids) in the drink. These imperfections and solids are called nucleation points. The CO2 diffuses into these tiny pockets and blows them into bubbles, which are buoyant and float to the top and release the CO2 into the air. 

- Your tongue has lots of nucleation sites for bubbles to form, and that's where we like them as it tingles. So we're trying to keep the CO2 dissolved into liquid until it hits our tongue. 

- When using the Perlini (or say if you wanted to create a bottled soda) you want top keep nucleation sites out of the container. Thus you want to avoid having solids (like bits of citrus from fresh juices- strain them instead).

- Also, the surface area of ice has lots of nucleation points. So you want to decrease the total surface area of ice, by using larger cubes rather than chipped ice. 

- The Perlini is meant to be shaken like a cocktail shaker, but when you do this bubbles form in the shaker. Thus they recommend waiting until the bubbles settle down before cracking open the shaker- otherwise it can foam over. Viscious liquids (liqueurs, milk) will hold bubbles for longer, so you need to wait longer for the shaker to settle before depressurizing. 

- You're also not supposed to strain the liquid coming out of the strainer when you pour the cocktail. There is a built-in strainer to keep the ice out of the drink, but double-straining will add more nucleation points and fizz while you're pouring it through the strainer. Instead, strain any drink before putting it in the shaker. This cuts down on nucleation points from the pulp, etc. before you shake it. Also, pouring it on new ice will increase nucleation points as well. 

- Carbonated beverages taste more tart than non-carbonated beverages. This is because CO2 dissolved into water produces carbonic acid, which itself is flavorless but somehow adds the perception of tartness. 

- To adjust for the above, you should adjust citrus cocktail recipes towards the sweeter side so they come into balance when carbonated.

- Egg white (and other high-protein) drinks are going to be problematic as they are very foamy. 

- "The acidity from the carbonic acid can interact with the tannins of wood-aged spirits in a way that emphasizes acerbic notes in their flavor profi les, requiring extra care in optimizing recipes." Weird. 

I am excited to crack this thing open and give it a try. I am especially curious to experiment on how carbonation affects the perception of tartness and tannins!