Sodium Benzoate and Benzoic Acid

Benzoic acid is found naturally in a wide variety of plants. It was isolated in the sixteenth century, but not commercially produced until the end of the nineteenth century. Researchers discovered in 1875 that this compound had potent antifungal properties, was relatively tasteless in foods, easy to make, and inexpensive. Sodium benzoate was the first chemical preservative approved for use in foods. Benzoic acid is most effective against fungi, yeasts, and bacteria in acidic environments. Proposed mechanisms of action include changes in cell membranes, loss of energy generation, reduction of intracellular pH, and inhibition of specific enzymes. Acquired resistance to benzoic acid depends on several factors including the microorganism and the environment from which it was originally isolated. It can be directly metabolized by microorganisms both aerobically and anaerobically. Certain food constituents may also affect its potency. Benzoate does not appear to be accumulated in humans and may be effective in reducing the frequency of urinary tract infections. However, allergic reactions (asthma and skin rashes) can occur in sensitive individuals. Benzoic acid and sodium benzoate are used in many food systems worldwide. More recent applications include addition to processed meat products, and incorporation into polymer coatings and in “active” packaging for foods. One proposed application has been as a substitute for antibiotics used in livestock feeds. Because of the long history of benzoate use in foods, the present chapter offers an extensive review of both research and commercial applications for the reader. In the future, combinations of preservatives (e.g., sodium benzoate and potassium sorbate) may offer enhanced protective effects (synergism), especially if combined with hurdle technology. This may address greater demand for more unique foods with less processing and less addition of chemical preservatives.