Effect of metal cation crosslinking on the mechanical properties and shrimp freshness monitoring sensitivity of pectin/carboxymethyl cellulose sodium/anthocyanin intelligent films.

Although many preparation methods have been reported so far, it is still a great challenge for intelligent packaging films with both excellent mechanical properties and very high sensitivity. Herein, we report a facile method to prepare performance-enhanced pectin (PC)/carboxymethyl cellulose sodium (CMC)/anthocyanins (ACNs)/metal ion films by crosslinking with metal ions (Zn, Mg and Ca). Cross-linking reaction between PC/CMC and metal ions significantly improved water resistance and mechanical properties of composite films (P < 0.05). Even at high relative humidity (RH = 84 %), cross-linking of Ca, Mg, and Zn significantly increased the tensile index of the films by 1.37, 1.41, and 1.52 times (P < 0.05), respectively. Moreover, the complexation of metal ions/polysaccharides with ACNs reduced the decomposition rate of ACNs, improved the storage stability and antioxidant capacity of ACNs, and also increased the sensitivity of the colorimetric response of the indicator films in monitoring shrimp freshness. Thus, with this high sensitivity, the Red, Green and Blue (RGB) values of the films can be determined using a mobile phone application to monitor shrimp safety in real time. These results suggest that ACNs-metal cation-polysaccharide composite films have great potential for smart packaging applications.