Benzoic Acid

About This Product

Benzoic acid is the simplest aromatic carboxylic acid, formula C7H6O2, carrying CAS number 65-85-0 and the European food additive number E210. It occurs naturally in cranberries, prunes, cinnamon and cloves, and is manufactured for food use by the partial oxidation of toluene. It is supplied as a white crystalline powder or flake with a faint balsamic odour, sparingly soluble in cold water and freely soluble in ethanol.

Its preservative action depends on pH. Only the undissociated acid crosses the microbial cell membrane, where it acidifies the cytoplasm and disrupts energy metabolism, and benzoic acid has a pKa of about 4.2. In practice activity falls away sharply above pH 4.5 and is strongest between pH 2.5 and 4.0. It is most effective against yeasts and moulds, with weaker activity against bacteria. Where a product is less acidic, or where cold-water solubility matters, the sodium salt is used instead.

Typical use is 0.05 to 0.1 percent, equivalent to 500 to 1,000 ppm, in carbonated soft drinks, fruit juices, pickled vegetables, sauces, dressings and jams. One formulation caution is well documented: benzoate and ascorbic acid together, under heat or light, can form trace benzene, so beverages combining the two need to be assessed rather than assumed safe.

Bio Green Foods supplies benzoic acid to a food-grade specification confirming assay, melting range, heavy metals and residue on ignition against the applicable monograph.