The effect of nisin and garlic (Allium sativum L.) essential oil separately and in combination on the growth of Listeria monocytogenes

In the present study, the anti-listerial activity of the nisin and garlic (Allium sativum L) essential oils (GO) alone and in combination was investigated at different temperatures (20 and 30 degrees C), pH (6.8, 5.6 and 4.8) and NaCl concentrations (0, 0.5, 2.5 and 4.5 g/100 mL). Minimum inhibitory concentrations (MICs) against Listeria monocytogenes were assessed for the nisin and essential oil. Furthermore, for combinations of the antimicrobials, the Differences in Population (DP) method were used to determine their effect. Both essential oil and nisin possessed considerable antimicrobial effects on the microorganism. The MICs for nisin and GO were 12.5 IU/mL and 100 mu g/mL, respectively. Regardless of NaCl concentration and temperature, the anti-listerial activity of both GO and nisin was strongly influenced by pH. Moreover, at the same temperature, and regardless of pH value, the growth of the organism was also affected by increasing NaCl concentration. In combination, the DP was related strongly to the agent's concentration and media pH. Meanwhile, among all combined systems, the effect of the combination (EC) of nisin with GO at 30 degrees C, pH 5.6 and 0 g/100 mL NaCl, showed significant anti-listerial activity (P <= 0.05). (C) 2011 Elsevier Ltd. All rights reserved.