Inhibition of Staphylococcus aureus in broth and meat broth using synergies of phenolics and organic acids

This study assessed the occurrence of an enhancing inhibitory effect of the combined application of thymol and carvacrol with lactic and acetic acid against Staphylococcus aureus using the determination of Fractional Inhibitory Concentration (FIC) index and kill-time assay in meat broth and in a food model (meat). Minimum Inhibitory Concentration (MIC) of carvacrol and thymol were 1.25 and 0.6 µL/mL, respectively. FIC indices of the combined application of the phenolic constituents and organic acids were 0.5 suggesting a synergic interaction. No difference (p > 0.05) was found among the bacterial counts for the meat broth added of the phenolics alone or in combination with lactic acid at sub-inhibitory concentrations. Contrarily, the bacterial counts found for the meat broth added of the phenolics alone were significantly lower (p < 0.05) than the counts obtained for the broth added of the combination of phenolics and acetic acid. No difference (p > 0.05) was found among the bacterial counts for the meat model added of phytochemicals alone and in combination with the organic acids. The tested antimicrobials alone or in mixture provided smaller anti-staphylococcal effect in meat broth than in meat model. These results could arise as an interesting approach for the improvement of food preservation using more natural procedures, considering the current demand of consumer and sensory quality of foods.