Inhibition of Listeria monocytogenes in minced beef by combined effect of oregano essential oil and caprylic acid

Both oregano essential oil (OEO) and caprylic acid (CA) are highly aromatic natural antimicrobials; their individual application in food is therefore limited. Their combined additive effect we proved previously in vitro. Following mixtures (v/w) were tested in minced lean beef inoculated with 6 strains of L. monocytogenes at concentration of 5 log cells/g: 0.25% of CA (MIC in vitro) + 0.1% of OEO (2×MIC); 0.5% CA (2×MIC) + 0.05% OEO (MIC); and both mixtures with 0.1% of citric acid. The treated meat was vacuum packed and stored at 3 ± 1 °C for 15 days. Approximately a 0.5 log reduction was observed at all experimental groups in comparison with the control samples (with distilled water) from day 6 to the end of storage. No differences in L. monocytogenes counts were found between the experimental groups. In sensory evaluation (odour, colour, overall acceptability) the mixtures with 0.1% of OEO showed during the whole experiment better scores in
odour and overall acceptability than the control group.