Antibacterial efficiency of Spanish Satureja montana essential oil against Listeria monocytogenes among natural flora in minced pork

The purpose of this study was to examine the effectiveness of winter savory (Satureja montana) essential oil (EO) for control of growth and survival of experimentally inoculated Listeria monocytogenes serovar 4b (10(4) CFU/g) among natural flora in minced pork. EOs of French thyme (Thymus vulgaris F) and rosemary (Rosmarinus officinalis) cultivated in the same region of Aragon (northeastern Spain) were used as reference ingredients. The EOs obtained by hydrodistillation were added at concentrations of 0.25, 0.5, 1, and 2.5 mu l/g (vol/wt), and the samples were kept at 4 degrees C in air for up to 7 days. The populations of L. monocytogenes and total viable bacteria were determined in the control and treated samples at 0, 1, 3, 5, and 7 days. Moderate activity of S. montana EO against L. monocytogenes was observed (at 2.5 mu l/g, reductions of 0.27 log CFU/g by day 3 and 0.61 log CFU/g by day 7), with higher activity against aerobic flora. The greatest reduction in aerobic flora was on day 3 (at 2.5 mu l/g) from 1.10 to 1.45 log CFU/g. S. montana EO was comparable to T. vulgaris F EO in listericidal activity, but R. officinalis EO was ineffective against the L. monocytogenes and aerobic flora in the minced meat model. The similar to 3-log reduction in aerobic flora with T vulgaris F EO at 0.25 to 2.5 mu l/g after 5 days of storage was the most significant reduction. Depending on sensory considerations, the addition of active EOs in combination with other preservation techniques for synergistic effects may provide alternatives to synthetic chemical preservatives. Suggestions on relationships between chemical composition and biological activities of EOs are outlined.