carbonation

, in the context of spirits and cocktails, refers to a process in which carbon dioxide gas is dissolved into a liquid under pressure. When a carbonated liquid is subsequently exposed to normal atmospheric pressure, the carbon dioxide comes out of solution, and small bubbles form.

Several factors influence the rate and size at which the bubbles of carbonation form, the two most important being the temperature of the liquid and the prevalence of nucleation sites. At temperatures above freezing, the solubility of carbon dioxide in water increases as temperature decreases, leading to slower release of carbon dioxide at lower temperatures. Nucleation points consist of microscopic imperfections or dust on the interior surface of glassware, particles present in the liquid, and features on the surface of ice cubes, garnishes, and other items that may be introduced into the liquid. These sites contain small pockets of trapped gas that increase in size with the addition of carbon dioxide until they grow large enough for a portion to break away and rise to the surface as a bubble, after which the process repeats with the portion of gas that remains trapped. Carbon dioxide therefore comes out of solution at a slower rate for colder liquids and liquids with fewer nucleation sites compared to warmer liquids and liquids with more nucleation sites, and as a result such liquids retain carbonation for a longer period of time.

Carbonation has several characteristic effects on flavor. Small bubbles bursting on the tongue produce a “fizzy” or “prickly” sensation that involves both the tactile and pain senses. The release of carbon dioxide can influence retronasal olfaction, the process in which odor molecules pass upward from the oral cavity to olfactory receptors in the back of the nasal cavity. Carbonation also produces a mildly sour flavor as a result of carbon dioxide and water reacting to form low concentrations of carbonic acid, in addition to which there is some evidence that carbonation itself may have a direct effect on the sour-sensing taste receptors in the mouth.Carbonation may be achieved by a variety of means including introduction of carbon dioxide from an external supply of pressurized gas, by sealing the ingredient together with a limited amount of dry ice or as a byproduct of natural fermentation. Because most edible ingredients contain a substantial proportion of water, these techniques can also be used to carbonate non-liquid foods such as fruits and vegetables that may then be used as a garnish or other component of a drink preparation.

The most common way carbonation is incorporated into a mixed drink is through the inclusion of a pre-carbonated liquid such as seltzer water, soda, or sparkling wine, which practice has given rise to several canonical families of drink such as the highball, fizz, daisy, and rickey, to name a few. See Collins; Daisy; Fizz; Highball;, Rickey. Bartenders have also begun to experiment with carbonating entire cocktails using specialized equipment, in which case care must be taken that the ingredients have been treated to contain minimal particulate matter, which would otherwise cause the rapid dissolution of carbon dioxide due to an overabundance of nucleation sites.

See also molecular mixology, wines, sparkling, still.

Arnold, Dave. Liquid Intelligence. New York: Norton, 2014.

Myhrvold, Nathan, Chris Young, and Maxime Bilet. Modernist Cuisine: The Art and Science of Cooking. Bellevue, WA: Cooking Lab, 2011.

By: Samuel Lloyd Kinsey