Antimicrobial activity of Pistacia lentiscus and Satureja montana essential oils against Listeria monocytogenes CECT 935 using laboratory media: Efficacy and synergistic potential in minced beef

The aim of this study was to optimize the antimicrobial efficacy of plant essential oils (EOs) for control of Listeria monocytogenes (L monocytogenes) serovar 4b CECT 935 using laboratory media and minced beef stored at 5 +/- 1 degrees C. Commercial EOs obtained from leave parts of Mediterranean Pistacia lentiscus (P. lentiscus) and Satureja montana (S. montana) were analyzed by gas chromatography-mass spectrometry (GC MS). The main components of EOs obtained were beta-myrcene (15.18%) and carvacrol (29.19%), respectively for P. lentiscus and S. montana. The in vitro antimicrobial activity of both EOs was evaluated against L monocytogenes using the agar diffusion technique, the minimum inhibitory concentrations (MIC) were also determined against the same microorganism using the broth micro-dilution method. According to the diameters of inhibition, S. montana EO had more antibacterial effects than that from P. lentiscus. MICs showed a range of 0.03 and 0.10% (vol/vol) respectively for S. montana and P lentiscus. S. montana and P. lentiscus EOs were added respectively in minced beef (twofold MIC values) at 0.06 and 0.20%, experimentally inoculated with L monocytogenes at a level of 3 x 10(5) CFU/g and stored at 5 +/- 1 degrees C during one week. S. montana EO was the more effective (P < 0.05) against target bacteria. P. lentiscus EO also demonstrated antibacterial effect against the same bacterium. EO combinations were also investigated in minced beef and P lentiscus combined with S. montana had synergistic effects. This work shows that the combined EOs might be more effective against L monocytogenes when applied to minced beef at the ratio of 1/1 to 2/2 according to the MIC values. Sensory evaluation revealed that minced beef treated with EOs was acceptable by panelists at the levels used. (C) 2011 Elsevier Ltd. All rights reserved.