Preparation and properties of cinnamon-thyme-ginger composite essential oil nanocapsules

Essential oils (EO) as one of natural antimicrobials possess excellent antibacterial, antifungal and antioxidant properties. However, their main components are easy to be oxidated and deteriorated when EO was exposed to the oxygen, light and heat. In this study, cinnamon-thyme-ginger composite essential oil nanocapsules (CEO-NPs) were prepared with chitosan as the wall via ionic gelification reaction. The effect of the mass ratio of chitosan (CS) to tripolyphosphate (TPP), composite essential oils (CEO) and surfactant concentration and pH on the properties of the CEO-NPs were investigated in detail. The morphology and structures of CEO-NPs were measured by dynamic light scattering (DLS), fourier transformation infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), gas chromatography–mass spectrometry (GC–MS) and ultraviolet spectrum (UV). Meanwhile, the antibacterial property of CEO-NPs was determined by inhibition zone method. CEO-NPs with the size of 215 nm and zeta potential of 25.12 mv were obtained when the mass ratio of CS/TPP, CEO and fatty alcohol polyoxyethylene ether-9 (AEO-9) concentration and pH were 8:1, 1.8 g/L, 0.7 g/L and 5.26. FTIR demonstrated that CEO has been encapsulated into NPs. TGA showed that the thermal stability of CEO-NPs was improved compared with CEO and the loading capacity of CEO was 13.4%. GC–MS displayed that more than 90% ingredients of CEO had been encapsulated into NPs. UV indicated that CEO-NPs had the excellent sustained-release property. Furthermore, CEO-NPs showed a long-lasting antibacterial activity against Escherichia coli, Bacillus subtilis and Staphylococcus aureus. In all, CEO-NPs can be used as a potential long-term natural preservative.