Antifungal effects of sorbic acid and propionic acid at different pH and NaCl conditions

The effect of pH (7, 5.6, 3.5), NaCl concentration (3 to 20% w/v) and EDTA on the antifungal activity of sorbic acid and propionic acid (Ca salt) against Candida spp., Sporothrix sp., Fusarium sp., Penicillium spp., Paecilomyces sp. and Aspergillus spp. was investigated by the Spiral Gradient End Point Test. Sorbic acid was active against most yeasts and molds, and in the presence of EDTA, which enhanced the effect of sorbic acid, all the organisms tested were inhibited. Sorbic acid was most effective at low pH. The inhibitory effect of sorbic acid increased with increasing NaCl concentration for all test organisms. Propionic acid was not as active as sorbic acid, but when combined with EDTA the inhibition was improved for some of the molds tested. increasing or decreasing the pH did not change the antifungal activity of propionic acid. Synergistic effects of NaCl occurred at concentrations higher than 10%, but when EDTA was added, the inhibition was seen even at the lower NaCl concentrations.