Food preservative

Benzoic acid and its salts are used as a food preservative, represented by the E-numbers E210, E211,E212, and E213. Benzoic acid inhibits the growth of mold, yeast^[7] and some bacteria. It is either added directly or created from reactions with its sodium, potassium, or calcium salt. The mechanism starts with the absorption of benzoic acid in to the cell. If the intracellular pH changes to 5 or lower, the anaerobic fermentation of glucose through phosphofructokinase is decreased by 95%. The efficacy of benzoic acid and benzoate is thus dependent on the pH of the food.[8] Acidic food and beverage like fruit juice (citric acid), sparkling drinks (carbon dioxide), soft drinks (phosphoric acid), pickles (vinegar) or other acidified food are preserved with benzoic acid and benzoates.

Typical levels of use for benzoic acid as a preservative in food are between 0.05 – 0.1%. Foods in which benzoic acid may be used and maximum levels for its application are laid down in international food law.

Concern has been expressed that benzoic acid and its salts may react with ascorbic acid (vitamin C) in some soft drinks, forming small quantities of benzene.

Medicinal

Benzoic acid is a constituent of Whitfield's Ointment which is used for the treatment of fungal skin diseases such as tinea, ringworm, and athlete's foot.