EFFECT OF HYDROGEN ION CONCENTRATION ON THE TOXICITY OF SODIUM BENZOATE TO MICROÖRGANISMS

Abstract

The retarding action of sodium benzoate on rate of multiplication of Sac-charomyces ellipsoideus is much stronger at ph 2.5-4.5 than at 5.0-9. A similar relationship holds for the retarding effect of sodium benzoate on alcoholic fermentation by this microorganism. The concentration of benzoate required to prevent growth of S. ellipsoideus, S. cerevisiae, a mucor mold, 2 penicillium molds, 3 strains of mycoderma yeast, a lactic acid bacterium, a vinegar bacterium, B. coli, B. subtilis and B. sporogenes was greatly affected by pH of medium. Much more benzoate was required near neutrality, e.g., Ph 5-8, than in the moderately acid range, 2.5-4.5. While these observations are primarily of scientific interest, they also have an important bearing on the preservation of non-acid foods such as ripe olives, avocado pulp and non-acid vegetables by sodium benzoate. Preliminary experiments have proved that similar relationships hold for certain other food preservatives.