Nanoemulsions of Trachyspermum copticum, Mentha pulegium and Satureja hortensis essential oils: formulation, physicochemical properties, antimicrobial and antioxidant efficiency

In this study, nanoemulsions (NEs) of Trachyspermum copticum (TCEO-NE), Mentha pulegium (MPEO-NE) and Satureja hortensis (SHEO-NE) essential oils were formulated and characterized. Their chemical composition was analyzed by gas chromatography/mass spectrometry. The NEs were formulated by ultrasound method using 15% EO (w/w), 80% water (w/w) and 5% surfactant (w/w). The droplet size, zeta potential, polydispersity index (PDI) and surface tension were measured. The NEs were characterized by ATR-FTIR. Their antimicrobial activity against four food-borne pathogens and their antioxidant effect were examined by DDPH and FRAP assays. MPEO-NE showed the smallest droplet size (125.40 nm) and the lowest PDI (0.37). The count of S. aureus decreased from 6.52 to 3.54 log cfu/ml after 2 h likely due to the presence of pulegone, germacrene D and isopulegone in M. pulegium EO while TCEO-NE had the most desirable IC50 value measured by FRAP test and 82.47% inhibitory activity against DPPH at concentration of 3 μg/ml. This high antioxidant activity could be attributed to thymol, limonene and α-terpinene in T. copticum EO. The results revealed that TCEO-NE and MPEO-NE could be incorporated into the food packaging materials to increase the shelf life of foods because of their favorable properties, antimicrobial and antioxidant activities. Therefore, they can be considered as natural alternatives for synthetic preservatives, however, some investigations are necessary to evaluate their use in food, potential health risks, and consumer acceptance.