Inhibition of foodborne pathogen bacteria by essential oils extracted from citrus fruits cultivated in Sicily

The antagonistic activity of the essential oils (EOs) extracted by hydrodistillation from the fruit peel of several citrus genotypes (pummelo, grapefruit, orange, kumquat, mandarin and lemon) was evaluated against foodborne pathogen bacteria (43 strains of Listeria monocytogenes, 35 strains of Staphylococcus aureus and 14 strains of Salmonella enterica). Five commercial EOs were used for comparison. Most of the EOs were more effective against the Gram-positive bacteria rather than Salmonella. EOs of lemon genotypes 14 and 15 showed the best results in terms of number of strains inhibited and width of the inhibition zone. The most susceptible strain of each species (L. monocytogenes 133, St. aureus 473 and Salmonella Newport 50404) was used as indicator for the evaluation of the minimum inhibition concentration (MIC) of the EOs 14 and 15. The last two EOs, EO 16 (showing the weakest inhibition power among lemon EOs), and the commercial EO L (lemon) were analysed for their chemical composition. A total of 30 major compounds were identified by gas chromatography/mass spectrometry (GC/MS) and the oxygenated monoterpenes were suggested to be implicated in the process of bacterial inhibition by citrus EOs.