Undissociated benzoic acid is highly lipophilic and easily penetrates the cell membrane into the cell, interferes with the permeability of the cell membrane of microorganisms such as bacteria and mold, and inhibits the absorption of amino acids by the cell membrane. The benzoic acid molecule entering the cell inhibits the activity of the microbial cell respiration enzyme system, and reduces the reaction rate catalyzed by phosphofructokinase in anaerobic respiration by 95%, thereby playing a preservative effect.

Sodium benzoate is an acidic preservative. It is generally used under acidic conditions and can be converted into active benzoic acid under acidic conditions. Therefore, the anti-corrosion mechanism is the same as benzoic acid. Its antiseptic function is best when the pH is 2.5-4.0. There is no bactericidal and bacteriostatic effect in alkaline medium. Because the water solubility of sodium benzoate is much greater than that of benzoic acid, it is easier to dissolve and disperse in water media, and it is stable in the air, so it is more commonly used than benzoic acid.