Sodium Benzoate
What it does
Preservative in acidic foods and drinks.
How it's made
Sodium salt of benzoic acid, synthesised.
Sodium benzoate is the sodium salt of benzoic acid and a very common preservative, used to stop the growth of yeasts, moulds and bacteria in acidic foods and drinks such as soft drinks, fruit juices, pickles, sauces and dressings. It is chosen over benzoic acid because it dissolves readily in water.
It is made by neutralising benzoic acid (produced by oxidising toluene) with a sodium base such as sodium hydroxide or sodium bicarbonate. The reaction yields the soluble sodium salt, which is then purified.
The salt is crystallised or spray-dried into a white powder or granules. In the acidic foods where it is used, it converts to active benzoic acid to do its preserving work. One point of note: in the presence of vitamin C and heat, benzoates can form traces of benzene, so manufacturers control formulations to prevent this, and it carries the children's activity-and-attention advisory when used alongside certain colours.
Possible reactions
Linked to hyperactivity in some children (with certain colours); may affect asthmatics/aspirin-sensitive people.