COMBINATION EFFECT OF ESSENTIAL OILS OF SOME HERBS WITH MONOLAURIN ON GROWTH AND SURVIVAL OF LISTERIA MONOCYTOGENES IN CULTURE MEDIA AND CHEESE

The antibacterial activity of tarragon, pennyroyal and spearmint EOs against Listeria monocytogenes in culture medium and fresh white cheese was evaluated alone, and in combination with monolaurin. Spearmint essential oil (EO) was the most effective, with minimum inhibitory concentration of 0.2% (v/v). The combination of monolaurin with EOs had an additive effect and fractional inhibitory concentration index of monolaurin-tarragon EO combination was the lowest (0.66). All the EOs, when added alone in the cheese, revealed the antibacterial effect that was directly related to the increase in their concentrations. Adding of tarragon EO plus monolaurin not only introduced the greatest inhibition compared with the other EOs, but also introduced listericidal activity; no bacteria were detected at combination of 0.6% Tarragon EO with 400 ppm monolaurin after 7 days of storage. The results of this study suggest the use of combination of these substances at low concentrations to control growth of L. monocytogenes in food commodity.