The short answer is that carbon dioxide gives drinks their fizz factor. Beverages, especially cold ones, have a certain amount of carbon dioxide gas dissolved in them. When the gaseous carbon dioxide mixes with water, it undergoes a chemical reaction to produce aqueous carbonic acid.
It is the carbonic acid that imparts the acidic flavor and a sweet sensation in your mouth. Without it, almost every soft drink tastes too bland – or ‘flat’ – as many call it. Have you ever gotten a soft drink from a restaurant that doesn’t have its beverage dispensing system balanced correctly? The taste of the resulting beverage is off putting to say the least.
However, what is so special about carbon dioxide that it is used in these cold drinks? Why don’t manufacturers use some other gas?
There are many reasons why carbon dioxide is the top choice as an additive in cold beverages. Let’s take a look at a few of them:
Perhaps the most important factor when it comes to mixing any gas with a liquid. Carbon dioxide is highly soluble in water; in fact, it is the most soluble of the common, non-toxic gases. Consider this… around 1.5 liters of carbon dioxide can be dissolved in 1 liter of water at normal atmospheric pressure.
Other common gases either don’t mix as well with water (e.g., helium, hydrogen), and if they do, they are usually toxic (e.g., hydrogen sulfide, ammonia, sulfur dioxide). Other gases are used in certain beverages, such as nitrogen, which gives beers such as Guinness its velvety mouth feel and dense foam head.
The reason carbon dioxide dissolves so well in water is that it reacts and forms carbonic acid, which is the primary cause behind the ‘fizz’. This fizz doesn’t just look cool, but also tastes good and has an oddly pleasant sound.
Carbon dioxide has no color and is flavorless. On its own, it is nothing much to write home about. On the other hand, the carbonic acid created during the carbonation process is what creates the fun fizz you love – and that tingly sensation. The colder the beverage and the tighter it is sealed, the fizzier your drink will be. So, when there is excess carbon dioxide, it will stay in the water until the pressure is released, the carbon dioxide escapes, and the beverage goes flat.
Carbonation also occurs naturally. This is true of naturally carbonated mineral water that absorbs the carbon dioxide from the ground. Carbonation can also be man-made, created during a process in which yeast and sugar combined to create alcohol as in homemade beer.
As mentioned earlier, there are a few of other gases that could serve as an alternative to carbon dioxide gas, but they are usually a bit too expensive for a casual drinker. Furthermore, carbon dioxide is readily available, so that also helps to bring down the cost.
You could oxygen instead of carbon dioxide, provided you are okay with all your drinks becoming undrinkable. Oxygen causes food and beverages to go bad, so you cannot use oxygen as an additive for preservation. Whereas, carbon dioxide does a great job preserving drinks for a long, long time.
Reference: Science ABC, (2019, December 4) Carbon Dioxide in Drinks: Why Is Carbon Dioxide Mixed in Cold Drinks & Beverages (https://www.scienceabc.com/eyeopeners/why-is-carbon-dioxide-mixed-in-cold-drinks-and-beverages.html)