Multifunctional halochromic packaging materials: Saffron petal anthocyanin loaded-chitosan nanofiber/methyl cellulose matrices

A new generation of eco-friendly packaging materials is required to improve food quality, safety, nutritional value, shelf-life, and sustainability. In this study, a novel multifunctional halochromic packaging material was fabricated by immobilizing saffron petal anthocyanins within a biopolymer matrix consisting of chitosan nanofibers and methyl cellulose. The gas barrier, light screening, physico-mechanical, and optical properties of the films were then characterized. The color of the multifunctional films depended on pH and ammonia gas levels as a result of changes in the molecular structure of the anthocyanins. The films changed from reddish/pink to violet to green to yellow as the pH was increased from 1 to 14, and went from violet to green/yellow when the ammonia vapor concentration was increased. Incorporation of the anthocyanins into the films also increased their tensile strength, light screening properties, antimicrobial activity (E. coli & S. aureus), and antioxidant activity (DPPH radical scavenging). Analysis of the microstructure and spectroscopic properties of the films showed that the anthocyanins were compatible with the surrounding biopolymer matrix. Finally, we showed that the anthocyanin-loaded films could be used as smart packaging materials for monitoring changes in the freshness of a model meat product (lamb) during storage.