Preparation and evaluation of Menthaspicata L. essential oil nanoemulsion: physicochemical properties, antibacterial activity against foodborne pathogens and antioxidant properties

In this study, nanoemulsion of Menthaspicata L. essential oil (MSEO) was successfully formulated and characterized. The chemical composition of MSEO was analyzed by gas chromatography-mass spectrometry. MSEO nanoemulsion was prepared by ultrasonication method and mixing the MSEO (10% w/w) with surfactant (5% w/w) and water (85% w/w). Damaging effect of MSEO nanoemulsion was evaluated on the cell membrane of common foodborne pathogens (Salmonella Typhimurium, Staphylococcusaureus, Escherichiacoli, Bacilluscereus, and Listeriamonocytogenes) using scanning electron microscopy and it was compared with free oil. Also, the activity of MSEO nanoemulsion was studied on the growth behavior of bacteria during storage at 35 degrees C for 72 h. The antioxidant activity of pure oil was compared with its nanoemulsion using 2,2-Diphenyl-1-picrylhydrazyl. The mean droplet size (51.46 nm), Polydispersity index (PDI) value (0.296), and Zeta-potential (- 13.2 mv) of oil nanoemulsion were determined. The bacterial cells were remarkably disintegrated and the levels of cell membrane damages by nano-encapsulated oil were higher than free oil. The activity of MSEO nanoemulsion at sub-inhibitory concentrations against the growth behavior of pathogenic bacteria was better than pure oil. Also, the radical scavenging activity of oil was significantly (p < 0.05) increased after incorporation into nanoemulsions and the IC50 value was decreased by 17.05 +/- 0.03%. In the present study, a food-grade nanoemulsion of MSEO was successfully produced by the ultrasonic emulsification method. The results demonstrated that nanoemulsions containing MSEO can be used, as a promising natural preservative, to increase the shelf life of food products and beverages.