Carbon Dioxide
What it does
Carbonation; packaging gas.
How it's made
Captured/compressed gas.
Carbon dioxide is the gas that puts the fizz in carbonated drinks, and it is also used to create a protective atmosphere in food packaging (to slow spoilage) and to chill or freeze foods as "dry ice". It is a normal, harmless gas, the same one we breathe out and that plants use to grow.
Food-grade carbon dioxide is collected and purified from several sources. Much of it is captured as a by-product of industrial processes such as fermentation (for example, from breweries and bioethanol plants) or from ammonia manufacture, where large amounts of pure carbon dioxide are released. The captured gas is cleaned, dried and compressed.
Careful purification removes impurities so that it meets strict food-grade standards, after which it is liquefied under pressure for storage and transport. In drinks it is dissolved under pressure to create carbonation; in packaging it displaces oxygen to extend shelf life; and as a solid (dry ice) it provides intense cooling.
Possible reactions
Generally safe; the fizz in drinks.