Combinational effects of Trachyspermum ammi and Zataria multiflora Boiss essential oils on some pathogenic food-borne bacteria

Application of natural compounds including essential oils (EOs) is an effective method to fight against the growth of bacterial pathogens in food. This study was conducted to determine the combinational effect of Trachyspermum ammi and Zataria multiflora Boiss essential oils on some pathogenic food-borne bacteria. The effect of different concentrations of Trachyspermum ammi and Zataria multiflora Boiss was assessed individually and/or in combination, using microdilution broth method to determine the minimal inhibitory concentration (MIC) effect on the pathogenic food-borne bacteria including E. coli O157: H7, Salmonella typhimurium, Listeria monocytogenes, Bacillus cereus, and Staphylococcus aureus. Moreover, the effect of EOs was analyzed, individually or in combination, on B.cereus and E.coli growth curves. Combination of Trachyspermum ammi and Zataria multiflora Boiss essential oils showed a synergistic effect against B. cereus and S. aureus and additive effect on E. coli, Salmonella typhimurium and Listeria monocytogenes. The results of growth curve analysis of the combinational effects of these two EOs showed that they decreased the rate and increased the lag phase of bacterial growth, especially for B.cereus. This finding has an important value in food microbiology. This study showed that T. ammi, and Z. multiflora Boiss essential oils were effective against bacterial growth, especially when they are used in combination. Based on this study it is suggested that their potential application to be considered in food industry