Intelligent poly (vinyl alcohol)-chitosan nanoparticles-mulberry extracts films capable of monitoring pH variations.

The aim of this study was to prepare a visually responsive intelligent film based on poly (vinyl alcohol) (PVA), chitosan nanoparticles (CHNPs) and mulberry extracts (MBE). CHNPs were first prepared by using ionotropic gelation method to enhance the mechanical properties of PVA based films. The morphology, particle size, zeta potential and crystallinity of CHNPs were measured. The resultant CHNPs were spherical with a diameter of 381.2nm, with high stability and a zeta potential of 49.1±1.33mV. The film with 6% CHNPs (P-C6) had the highest tensile strength (∼73.43MPa). MBE was incorporated into the P-C6 film. The film containing 20% MBE had the highest tensile strength and showed visible color responses to variations across pH 1-13. The film was tested by monitoring the spoilage of fish. The color of the film changed from red to green as the fish spoiled. Therefore, the pH responsive intelligent film developed here can be used as a package label to detect food spoilage.