Carbon dioxide (CO2)
Carbon dioxide is the only gas suitable for providing the
effervescence (fizziness) in soft drinks. This is because it is
non-toxic, inert, virtually tasteless and is convenient for bulk
transportation and storage.
When dissolved in water, carbon dioxide is sparingly soluble
providing a characteristic mouth-feel and taste to the product.
This means some of it remains as the gaseous form, while a
proportion dissolves in the water. In addition, carbon dioxide has
a preserving property in certain conditions, where it inhibits the
development of harmful aerobic micro-organisms. However, it is not
used as a substitute for other methods to ensure microbiological
safety. Carbon dioxide also serves to provide internal pressure in
canning to prevent distortion in the container.
The amount of carbonation is dependent upon the type of soft drink.
Lightly carbonated soft drinksare usually fruity, whereas lemonade
and cola have medium carbonation and mixers are highly
carbonated.
Carbon dioxide can occur naturally and some bottled water are
naturally sparkling. Carbon dioxide can also be a by-product of the
petroleum and gas industries and of alcohol fermentation in beer
and spirit production.