Benzoic Acid

How it's made

Synthesised; occurs naturally in some berries.

Benzoic acid is a preservative effective against yeasts, moulds and bacteria, used particularly in acidic foods and drinks such as soft drinks, pickles, fruit products and sauces. It occurs naturally in some fruits (notably cranberries) and in other plants.

For food use it is manufactured by chemical synthesis, most commonly by oxidising toluene (a petroleum-derived aromatic) with air in the presence of a catalyst, which converts it to benzoic acid. This is the same efficient industrial route used to make benzoic acid for many purposes, purified to food grade.

The acid is purified and crystallised into a white powder or flakes. It works only in acidic conditions, so it is used in low-pH products, and because benzoic acid itself is not very soluble in water, its sodium salt is often used instead where better solubility is needed.