Chemical composition and antibacterial and antioxidant properties of commercial essential oils

The aim of this work was to determine the effectiveness of 17 essential oils to inhibit the growth of seven food-borne spoilage and pathogenic bacterial strains (Brochothrix thermosphacta, Escherichia coli, Listeria innocua, Listeria monocytogenes, Pseudomonas putida, Salmonella typhimurium and Shewanella putrefaciens). Additionally, the antioxidant activity (by free radical scavenging activity and ferric reducing power) and the chemical composition of these essential oils were evaluated. All essential oils inhibited the growth of at least four bacteria tested, and lower values of minimum inhibitory concentration (<3.0mgmL ^-1) were needed to inhibit P. putida. The highest reductions (8.0logCFUmL ^-1) were achieved with coriander, origanum and rosemary essential oils for L. innocua, as well as with thyme essential oil for both Listeria strains. The results showed that for the evaluation of antibacterial activity of plant essential oils, bacterial counts should be performed instead of absorbance readings when using microdilution methods. Regarding the antioxidant activity, clove and origanum essential oils showed the strongest antioxidant properties. Essential oils showed a great variety of compounds in their chemical compositions, some of those with known antibacterial and antioxidant properties. In conclusion, all tested essential oils have very strong potential applicability as antibacterial and antioxidant agents for food and pharmaceutical industries.