This research was undertaken because of strikingly different experiences with sodium benzoate when taken by mouth in the following ways: (a) pure, as dry crystalline salt, or in aqueous solution; (b) in neutral or alkaline solutions, or in mixtures rich in fat, carbohydrate or protein, e. g., milk; (c) in acid vegetables or fruit, either warm, as in tomato soup, or cold, as in canned plums, peaches, tomatoes, etc.; (d) in beverages containing large percentages of organic acids, e. g., cider, lemonade, grape juice, etc.; (e) in mixtures containing inorganic acids, e. g., artificial gastric juice.
Brunton1 has compiled data that show the comparative arresting influence of various drugs on the action of ferments (Table 1). From these data it is evident that the inhibiting action of a given amount of benzoic acid in combined form, e. g., sodium benzoate, is very much weaker than when the benzoic acid is free.2
LUCAS DR. SOME EFFECTS OF SODIUM BENZOATE. JAMA. 1910;LIV(10):759-766. doi:10.1001/jama.1910.92550360001001b