Development of green halochromic smart and active packaging materials: TiO2 nanoparticle- and anthocyanin-loaded gelatin/κ-carrageenan films

Sustainable multifunctional halochromic nanocomposite films (“smart films”) were prepared using a casting method. Natural pigments (saffron or red barberry anthocyanins) and TiO2 nanoparticles were included in these films as pH-responsive color indicators and for light blocking, respectively, as well as for their other functional attributes. The film matrix was constructed from a network of crosslinked biopolymers consisting of gelatin and κ-carrageenan. The mechanical, morphological, spectroscopic, colorimetric, thermal, barrier, ammonia-sensitivity, antimicrobial, antioxidant, and biodegradable characteristics of the films were investigated. Moreover, the efficacy of the films was demonstrated by using them to monitor changes in the freshness of packaged fish during storage. Incorporation of TiO2 nanoparticles and natural anthocyanins significantly improved the mechanical and moisture resistance of the films. Spectroscopic analysis (ATR-FTIR and XRD) indicated the nanoparticles and pigments were dispersed throughout the biopolymer matrix, and identified the important molecular interactions involved (such as hydrogen and electrostatic bonding). The films changed color in response to alterations in the freshness of the fish samples, which was correlated to ammonia production during fish degradation. The presence of the anthocyanins and TiO2 nanoparticles increased the bacteriostatic properties of the smart films, as well as inhibiting oxidative reactions. The smart films were shown to be biodegradable, decomposing within ∼30 days under simulated environmental conditions. In conclusion, these biodegradable smart/active films may be suitable replacements for plastic packaging materials. Moreover, they are able to detect food deterioration and prolong shelf life, thereby improving quality and reducing waste.