Antibacterial effect of Juniperus communis and Satureja montana essential oils against Listeria monocytogenes in vitro and in wine marinated beef

Juniperus communis and Satureja montana essential oils (EOs) were chemically characterized and their activity against Listeria monocytogenes was evaluated. Antilisterial effect was determined in vitro and in situ, in red winemarinated beef, where the effect against common meat contaminants (aerobic heterotrophic mesophyll bacteria, Enterobacteriaceae and lactic acid bacteria) was also monitored. Microdilution assay on L. monocytogenes (strain ATCC19111 and three primoisolates) showed that minimal inhibitory concentrations (MICs) varied in the range 0.5-1% for both EOs. Effect of EOs mixtures was monitored in checkerboard assay revealing that all types of interactions including synergism were obtained only for isolates. In vitro time kill assay confirmed the mode of interactions: synergism for isolate from beef carcass (LMB), and its absence for ATCC19111 strain. The analysis of concentration dependent growth rates showed that estimated curve MIC values were notably lower than in microdilution assay (0.03-0.14%). In situ time kill assay against inoculated L. monocytogenes (ATCC19111 and LMB strains) and pre-existing meat spoiling contaminants was performed on marinated beef using EOs concentrations that were confirmed to be sensory acceptable. Basic red wine marinades and the ones containing each EO or their combination remarkably decreased the counts of all monitored groups comparing to saline control. The most pronounced effect was obtained with the marinade containing EOs mixture. For all monitored bacteria, the bactericidal effect during marination was followed by bacteriostatic effect during subsequent meat storage. Our results demonstrate for the first time the in situ efficacy of J. communis EO against meat contaminants and provide additional data on the preservation potential of S. montana EO.