There is growing interest in the development of natural antimicrobials to preserve foods. In this research, Sage (Salvia officinalis) essential oil was converted into a nanoemulsion using nonionic surfactants (Tween 80, Span 80) and high-intensity sonication. The antimicrobial activity of essential oil nanoemulsions (d z 222 nm) was compared to that of pure essential oil against food-borne bacteria (Escherichia coli, Shigella dysentery, and Salmonella typhi) using minimum inhibitory and bactericidal concentration (MIC and MBC) methods. The antibacterial activity of the nanoemulsion was four-times higher than the bulk oil against E. coli and S. typhi. Kinetic studies showed that the nanoemulsions could destroy all the E. coli in about 10 min, whereas <50% of the bacteria were killed using pure oil. The potential mechanism of antibacterial activity of the pure and nanoemulsified oils was investigated using protein release, nucleic acid release, and potassium leakage studies, as well as infrared and electron microscopy analysis of the cell membranes. The results showed extensive bacterial cell membrane damage after nanoemulsion treatment. These results indicate that conversion of sage oil into a nanoemulsion improved its antibacterial activity by enhancing its ability to promote the destruction of bacterial cell membranes.
