Why is carbon dioxide added to cold drinks?

Five reasons stacked up at once: (1) it's the most soluble of the cheap, non-toxic gases, so a lot of it dissolves under pressure; (2) it reacts with water to form carbonic acid, which gives soft drinks their tangy, prickly bite; (3) the dissolved CO2 escapes as bubbles when you open the bottle — the iconic fizz; (4) the mildly acidic environment inhibits bacterial and mould growth, preserving the drink; and (5) it's chemically stable and food-safe, and very cheap to produce industrially.

Which gas is in fizzy drinks?

Carbon dioxide (CO2). It is dissolved into the drink under several atmospheres of pressure and forms small amounts of carbonic acid in the water. When you pop the cap, the pressure drops and the CO2 comes out of solution as bubbles.

What is the chemical reaction when CO2 dissolves in water?

Most of the CO2 stays as dissolved gas, but a small fraction reacts reversibly with water: CO2 + H2O ⇌ H2CO3 (carbonic acid) ⇌ H+ + HCO3- (bicarbonate). The H+ ions are why a soft drink is acidic (pH typically 2.5–4) and why it tastes tangy.

Why not use oxygen or another gas instead of CO2?

Oxygen is far less soluble than CO2 and, worse, it would accelerate spoilage by oxidizing the flavours, colours and sugars in the drink. Most alternatives are either toxic (chlorine, sulfur dioxide, hydrogen sulfide, ammonia), flammable (hydrogen, methane), or barely soluble (helium, argon). CO2 is the rare gas that is cheap, food-safe, soluble, stable and adds desirable taste — all at once.

Can you drink carbon dioxide?

You already do, every time you drink a fizzy drink. Dissolved CO2 is harmless in normal amounts — the body produces CO2 as a metabolic waste product and exhales it constantly. Drinking large quantities of highly carbonated water can cause bloating and burping, but not poisoning.

Carbon Dioxide In Drinks:Why Is CO2 Mixed In Drinks & Beverages?

Table of Contents (click to expand)

What Is Carbonation?
Why Is Carbon Dioxide Used In Cold Drinks?

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Carbon dioxide is the gas of choice for soft drinks, sparkling water, beer and champagne because it dissolves readily under pressure, is the most soluble of the cheap, non-toxic gases, and reacts with water to form carbonic acid — which gives the drink its tangy, prickly “fizz.” It is also food-safe, chemically stable, and slightly acidic, so it inhibits the bacteria and moulds that would otherwise spoil the drink.

You may already know that soft drinks and certain cold beverages (e.g., beer) contain a certain amount of gaseous carbon dioxide. That’s why these bottles fizz when you shake them vigorously, and champagne and wine bottles open with a popping sound.

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Why Is Carbon Dioxide Mixed In Cold Drinks And Beverages?

What Is Carbonation?

Most cold drinks and other beverages contain a certain amount of carbon dioxide gas dissolved in them. When this gas comes in contact with water, it reacts chemically to produce aqueous carbonic acid (H₂CO₃), which is responsible for the tangy, slightly sour flavor and the tingly, almost-burning sensation on your tongue.

Water carbon dioxide carbonic acid bicarbonate hydrogen ion formula

Without it, most soft drinks would taste too bland or “flat,” as many say. But what makes carbon dioxide so special that it’s used in these drinks? And why don’t manufacturers opt for other gases instead?

Why Is Carbon Dioxide Used In Cold Drinks?

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:

Solubility

Carbon dioxide is highly soluble in water, making it the most soluble of the common, non-toxic gases. To put that in perspective, water can dissolve roughly its own volume of CO₂ gas at 1 atmosphere of pressure and room temperature — and that figure climbs sharply when the drink is chilled and bottled under 2–4 atmospheres of pressure, which is why a soft drink can hold so much fizz.

Bubbling soft drink — Carbon dioxide dissolves well with water. (Photo Credit : Pixabay)

On the other hand, other common gases, such as helium and hydrogen, do not mix well with water. If they do, they are usually toxic, like hydrogen sulfide, ammonia, and sulfur dioxide. However, some drinks do use other gases, but they tend to be more expensive and less commonly consumed by the general public.

Stability

Once the bottle is opened, the pressure drops and the dissolved CO₂ escapes as the bubbles we see — that’s the famous ‘fizz’ of a cold drink (the carbonic acid mostly handles the taste; the bubbles themselves are CO₂ gas coming out of solution). It doesn’t just look cool — it also has that oddly pleasant prickling feel on your tongue and a satisfying sound.

Fizzing cold drink — The fizz of a cold drink makes it more aesthetically appealing, at least to some people. (Photo Credit: Pxhere)

In short, carbon dioxide is incredibly stable when mixed with other water, unlike many other gases. It leads to the formation of carbonic acid (which is desired), unlike some other gases that would result in some nasty byproducts when mixed with cold beverages.

Cost

As mentioned earlier, a few other gases could serve as an alternative to carbon dioxide gas, but they’re usually a bit too expensive for a casual drinker. Furthermore, carbon dioxide is readily available, which also helps bring down the cost.

Preservation

Oxygen is more abundant than carbon dioxide in the atmosphere, so one may wonder if using oxygen in cold drinks makes more sense instead of carbon dioxide.

Sure, you could use oxygen instead of carbon dioxide, provided you’re okay with all your drinks becoming undrinkable. Oxygen causes food and beverages to spoil, so you can’t use oxygen as an additive. On the other hand, carbon dioxide does a great job preserving drinks for a long, long time.

Safety

Hypothetically, gases like methane might dissolve in water, but they are non-starters for beverages — methane is flammable and odourless, and would create explosion and leak-detection hazards in a beverage plant.

Additionally, using other gases, such as chlorine, is not recommended because they can be poisonous.

Let me offer you this drink containing dissolved carbon dioxide and assure you that its perfectly safe meme

Furthermore, the long-term environmental impacts of using a specific gas in cold drinks on an industrial scale should also be considered.

In summary, while other alternatives to carbon dioxide gas can be used in beverages, they differ in carbon dioxide’s safety, stability, availability, flavor, and affordability. Therefore, manufacturers prefer to use carbon dioxide for industrial-scale production.

Last Updated By: Ashish Tiwari

References (click to expand)