Uncovering The Chemistry of Carbonated Drinks
In 2014, food scientist Gérard Liger-Belair created a new, complex mathematical model solely to answer a whimsical question: how many bubbles are in the average flute of champagne?
His result?
Just a touch over 1 million.
Yet, when he tried to adapt his model to answer a similar question for beer, he made a surprising discovery: far more variables affected a beer’s bubble quantity.
In contrast to champagne, a beer’s style, container shape, and even small defects in the glass dramatically impact the drink’s fizziness. Thus, his 2021 follow-up paper could only offer a range: a typical beer has between 200,000 and 2 million bubbles.
While Liger-Belair’s model was innovative, he’s far from the first to approach the art of carbonation through chemistry and physics. Here, we unpack everything we’ve discovered so far about the chemistry of carbonated drinks.
What Makes A Drink Sparkle? The Carbonation Process
Carbonation is the act of dissolving CO2, a gas, into a liquid–usually something drinkable, like water or beer.
To effectively carbonate a beverage, it’s necessary to pressurize the CO2 and submerge it underneath the liquid’s surface. When the CO2 is forced into the beverage at a cool temperature, the water molecules enclose the CO2 molecules.
After this process, the beverage will contain forcibly dissolved CO2. As a result, a carbonated beverage in a sealed bottle or can has some CO2 in a dissolved form, a mixture of itself and water, and some in a gas form between the “ceiling” of the sealed container and the surface of the liquid.
Then, once the seal is broken or the lid is removed, the CO2 throughout the liquid reacts and rushes to the surface in the form of bubbles, forming a foamy “head.” The layer of bubbles, or fizz, creates a texture that “sparkles” on the tongue. The bubbles continue to form and rise as long as some CO2 remains in the drink.
It’s also possible to carbonate an unsealed drink in a glass, and people can carbonate certain alcoholic drinks through the fermentation process. The exact mechanisms, methods, and chemical reactions inherent to different carbonation processes vary to some extent, depending on a few different variables. Here’s what that means in practice.
The Chemistry & Physics of Fizz
The overarching principles of Physics and Chemistry give us a framework to understand the nature of carbonation. They also offer paths to model and predict the degree and experience of a given drink’s final “sparkle” after the carbonation process.
To understand the underlying principles, it’s vital to consider carbonic acid and pressurization.
Carbonic Acid
Carbonic acid is formed by a chemical reaction during CO₂’s dissolution. In essence, the combination of the CO₂ and the H₂O in the beverage react on a molecular level. The equation articulating this reaction is CO₂ + H₂O ≒ H₂CO₃. The reaction creates a molecule with two hydrogen atoms, one carbon atom, and three oxygen atoms.
Carbonic acid is a “weak acid.” Though it’s a relatively stable gas when floating in the air, in water the molecule will convert back into CO₂. The CO₂ within the H₂CO₃ will start separating itself from the surrounding water molecules, unless prevented from doing so by another force (pressure).
This de-conversion, or reversing reaction, will happen continually, just as the initial carbonic-acid-creating reaction will continue until equilibrium is reached.
When a seal is broken, the pressure is released, causing CO₂ from the diffused carbonic acid to break free and rise to the surface in its gas form. As the bubbles rise and break, releasing CO₂ into the air, the degree of CO₂ in the beverage decreases until the drink goes flat.
Pressurization
The pressurization aspect of the process brings Physics into the mix. In physical chemistry, there’s a gas constant, or principle of the nature and behavior of gasses, called “Henry’s Law.” It states, “The amount of dissolved gas in a liquid is directly proportional to its partial pressure above the liquid.”
Henry’s Law describes the principle that enables dramatic increases in carbonation in a given volume of liquid, simply by increasing the pressure of the gas pump. Increasing pressure both above and below the liquid’s surface increases the density of the gas pumped into a given volume of space. The dissolving is sustainable as long as that pressure is maintained.
CO₂ Reactions: Changing Temps, Elements & Ingredients
On top of the underlying chemical and physical principles, the science of carbonation accounts for variables. Differences in temperature, sweetness, and acidity can each alter the chemical reaction involved in carbonation.
Rule of Cool
Heat gives molecules kinetic energy, causing them to move around. The molecules in cooler liquids have less energy, so they’re unable to move around within the space as much or as quickly.
Moving slowly allows molecules of pumped-in CO₂ to connect with the H₂O molecules and form carbonic acid more readily, and also leaves more space to accommodate CO₂ molecules in their gas form.
Moreover, once the pressure is removed, the CO₂ molecules in a cold drink also have less kinetic energy, slowing their rise to the surface and keeping a cold drink fizzy longer.
Sugars & Sweeteners
Sugars and artificial sweeteners have multiple impacts on beverage carbonation. These include:
- Sugar molecules’ presence in a liquid blocks CO₂ from dissolving in the spaces those molecules occupy
- This can decrease the total level of carbonation in a drink
- Sugar “bumps” can become a surface, or “nucleation site,” on which bubbles form
- High concentrations of sugar can hinder bubble formation
- Even when CO₂ has effectively dissolved in the drink, the formation hindrance changes the resulting bubbles’ texture
- Different sweeteners, like stevia, can alter and reduce liquid surface tension
- This renders carbonation more visible and causes bubbles to break through the surface more quickly
Beverage Acidity
The acidity of a beverage similarly affects the result of carbonation. Since carbonation creates carbonic acid, it increases the acidity of the drink as a whole, lowering its pH. This creates a tang or sour note in a drink, which is sometimes desirable. Otherwise, it might need to be offset by some other aspects of the beverage.
Notably, nitrogenation doesn’t reduce pH as much as carbonation. So, it’s often a better choice for smoother beers and foaming highly acidic drinks, like cold brewed coffees.
How Much CO₂ Do Different Types of Drinks Contain?
A drink’s carbonation level is indicated with two measures: vol/vol CO₂ and g/L. Vol/vol CO₂ indicates how much CO₂ in its gas form has been dissolved in a given liquid volume of the beverage. Vol CO₂ will vary depending on the temperature and atmospheric level.
It can be easier to instead use the metric g/L: a similar ratio, one that specifically shows how many grams of CO₂ have been dissolved in a liter of liquid.
The degree of carbonation varies considerably from beverage to beverage. Fortunately, Quantiperm’s experts developed two comprehensive guides for your reference.
The first is, “Fizzy Perfection: A Complete Guide To Beverage Carbonation.” It dives deep into carbonation methods and results, and it offers an at-a-glance carbonation level chart to make it easy to reference. The chart details how much CO₂ is typical in different categories of soda, sparkling waters, fizzy teas & juices, and sparkling wines.
The second guide is, “Beer Carbonation Chart By Beer Style.” This chart is also intended as a quick reference—in this case, for brewers carbonating beers. It covers the typical degree of carbonation in seven popular styles.
Engineer Perfectly Carbonated Drinks With QuantiPerm
At QuantiPerm, we use cutting-edge science and technology to deliver best-in-class brewing solutions. Whether you need to automate carbonation, get control on dissolved oxygen levels with deoxygenation, or fingerprint your fermentation, we’ve got you covered.
For more information, contact us by phone or email using the details listed below.
