INFLUENCE OF SORBIC ACID ON THE GROWTH OF CERTAIN SPECIES OF BACTERIA, YEASTS, AND FILAMENTOUS FUNGI

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Abstract
The influence of sorbic acid on the growth of cultures, representing 66 species of filamentous fungi, 32 species of yeasts, and 6 species of lactic acid bacteria was studied. The pH of the culture medium was the principal factor controlling the effectiveness of sorbic acid as an inhibitor for microbial growth. All of the organisms studied grew in media containing 0.1% sorbic acid at pH 7.0. The yeasts and filamentous fungi were inhibited by this concentration of sorbic acid at pH 4.5 and the lactic acid bacteria were inhibited at pH 3.5. Certain species of yeasts and lactic acid bacteria were tested for growth in media containing 0.10% sorbic acid over a pH range from 3.5 to 6.8. The reduction in growth observed for these organisms paralleled the dissociation of sorbic acid over the pH range studied. The toxic action of sorbic acid appears to be directly related to the concentration of undissociated acid.