Antimicrobial Activities of Organic Acids Determined by Minimum Inhibitory Concentrations at Different pH Ranged from 4.0 to 7.0.

Abstract

Minimum inhibitory concentrations of organic acids against 15 strains of bacteria, 6 strains of yeasts, and 2 strains of molds were determined in the media with diffesent pH ranged from 4.0 to 7.0. Formic, acetic, and propionic acids showed almost similas activities of growth inhibition against most strains of microorganisms except that formic acid showed stronger activities to lactic acid bacteria and weak activities to fungi than other two acids. The activities of sorbic acid were different from those of other fatty acids such as acetic and propionic acids, and were stronger against yeasts and molds than to bacteria. The activities of lactic acid (D and L form) were most characteristic. It inhibited growth of all strains of lactic acid bacteria in any ranges of pH. On the contrary, there were no acitivities by lactic acid against fungi. Malic, tastaric, gluconic and citric acids showed rather weak acitivities to any kinds of microorganisms. Citric acid only showed moderate activities against some strains of lactic acid bacteria. Adipic acid showed very strong activity in lower pH ranges and no activities in the pH ranges above pH 6.0. Effect of pH on the antimicrobial activities of adipic acid was extensively large compased with those of other acids. And adipic acid showed almost no activity to fungi. These sesults elucidated that each organic acid had inherent antimicrobial activity individ- ually.