| Chitosan (CS) films prepared by casting-evaporation method, were processed by alkali leaching. Effects of alkali leaching on microstructure and physical properties of CS films were investigated. Chitosan-natural essential oils (NEOs) composite films were prepared by incorporating different concentrations of Florida mandarin oil (FMO), lavender essential oil (LEO) or Brazil sweet orange oil (BSOO) into chitosan films with casting-evaporation-alkali leaching method. Tween80and potassium hydroxide aqueous solution were used as emulsifier and lye, respectively. Microstructures of films were characterized by scanning electron microscope, Fourier transform infrared spectroscopy and X-ray diffraction. Influences of different concentrations (0%,2%,4%,6%,8%and10%) of natural essential oils to characters of the films, including appearance, thickness, tensile strength (TS), elongation at break (E), volatiles content (VC), water contact angle (WCA), water vapour permeability (WVP), total soluble matter content (TSMC), swelling index (SI) and antibacterial activity of films, were investigated. Results demonstrated that after alkali leaching, thickness, TSMC and SI of CS film decreased, meanwhile TS, E and WCA increased. Partial functional groups locations of CS matrix were occupied by NEOs, and vibration intensities of covalent bonds in CS matrix were impaired. TSMC, WCA and chitosan-acetate content of films increased with increase of NEOs concentraton. TS of films was increased by LEO incorporation, E of films could be increased by NEOs addition. Decrease of film VC and SI was caused by addition of NEOs. CS-LEO (2%) films had the lowest WVP (247.36±3.22mg-mm-kPa-1·h-1·m-2). CS-FMO (10%) possessed the best inhibitory ability on Escherichia coli, inhibition semidiameter was0.96±0.30mm. |
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