Characterization of edible films based on hydroxypropylmethylcellulose and tea tree essential oil

Edible films based on hydroxypropylmethylcellulose (HPMC) and different concentrations of tea tree essential oil (TTO) were prepared. Film-forming dispersions (FFD) were characterized in terms of rheological properties, particle size distribution and ζ-potential. In order to study the impact of the incorporation of TTO into the HPMC matrix, the water sorption isotherms, water vapour permeability (WVP), mechanical and optical properties of the dry films were evaluated. Results showed that the increase in TTO content promoted significant changes in the size and surface charge of the FFD particles. With regards to the film properties, the higher the TTO content, the lower the WVP and the moisture sorption capacity. In general, the addition of TTO into the HPMC matrix leads to a significant decrease in gloss and transparency and a decrease in the tensile strength and elastic modulus of the composite films. The properties of the films were related with their microstructure, which was observed by SEM.