Effect of different cation in situ cross-linking on the properties of pectin-thymol active film

Abstract

In this work, the effect of in situ cross-linking of different cations on the properties of pectin-thymol active films was investigated. Specifically, pectin-thymol composite films (P-T) were developed by solution casting method, and then P-T/Ca, P-T/Fe, and P-T/Cu films with enhanced properties were developed by in situ cation cross-linking in 50% (v/v) ethanol-water solution containing Ca2+, Fe3+, and Cu2+, respectively. The thickness, color, optical properties, water sensitivity, water vapor permeability, mechanical properties, antimicrobial properties and thymol release properties of films were investigated. The interactions and specific micromorphology of films were also analyzed using FTIR and scanning electron microscope. The results showed that Fe3+ and Cu2+ could be uniformly distributed on the film surface and diffused into the interior by external in situ cross-linking. And the water resistance of the composite pectin films was significantly enhanced by the in situ cross-linking with different cations. The P-T/Fe films exhibited excellent UV-barrier properties. The mechanical properties and water vapor barrier properties of cation cross-linked P-T films were also improved. In addition, this work indicated that “egg-box” model formed between the cation and pectin molecule has a slow release effect on thymol in pectin films, which provides a new idea for the controlled release of active substances in pectin films.