UV responded polyvinyl alcohol bio-active films containing oregano essential oil microcapsules by chitosan-incorporated TiO₂: Physical properties, release characterizations, bio-functional performances and applications

In the present study, with oregano essential oil (OEO) as the active ingredient and polyvinyl alcohol/citric acid (PVA/CA) as the composite matrix, ultraviolet (UV) responded PVA bio-active films incorporated with microcapsules, which were established by chitosan-incorporated titanium dioxide (TiO₂), were constructed. The UV light-triggered process changed the structure of films, including the degradation of PVA, the fracture of ester bonds and the breaking of glycosidic bonds. UV irradiation reduced the elongation at break, increased the light resistance ability, the surface hydrophobicity and the roughness, and accelerated the release of OEO in films. The release process of films in food simulations and air environment conformed to Fick's second law and the first-order dynamics model, which were attributed to the synergistic effects of the random diffusion and the structural relaxation that were promoted by UV irradiation, leading to the increase of release rate, antioxidant activities and antibacterial capacities of films. Finally, chicken thighs with UV responded PVA bio-active films had better quality and the films could be considered as active packages for preservation.