Background: Food borne pathogens are of the main concerns of food producers and consumers and Escherichia coli and Staphylococcus aureus create a lot of problems worldwide. The aim of this study was to evaluate antibacterial effects of monolaurin, sorbic acid and potassium sorbate on S. aureus and E. coli at different pH values and NaCl concentrations.
Methods: Micro-well dilution assay was used to determine antimicrobial potency of monolaurin, sorbic acid and potassium sorbate. First, stock solutions of each antimicrobial compounds were prepared and then two-fold dilution method was used to obtain final con-centrations of tested antimicrobials. A 96 well microplate was inoculated with different concentrations of antimicrobials and bacterial inoculums (final inoculums was approximately 5×10⁵ CFU/ml). After incubation, growth of E. coli and S. aureus were evaluated. Statistical analysis was made by the analysis of variance using SPSS software, version 16.0.
Results: The MICs of monolaurin, sorbic acid and potassium sorbate were respectively >4000, >5000, >10000 μg/ml for E. coli, and 128, 1250 and 2500 μg/ml for S. aureus. The results showed that all of these compounds had considerable effect on S. aureus while E. coli was less sensitive. It should be noted that, monolaurin had strong antimicrobial effect on E. coli when used in combination with ethylene diamine tetra acetic acid.
Conclusion: According to the results of this study, monolaurin and sorbates can be used effectively as food preservative and growth inhibitor of these food borne pathogens. Using NaCl and/or lower pH values may fortify their bacteriostatic effects.