Hydroxypropyl methylcellulose/microcrystalline cellulose biocomposite film incorporated with butterfly pea anthocyanin as a sustainable pH-responsive indicator for intelligent food-packaging applications

In this study, an environment-friendly pH-responsive indicator was prepared from hydroxypropyl methylcellulose/microcrystalline cellulose biocomposites (HMB) and butterfly pea (Clitoria ternatea) anthocyanin (BA). BA at concentrations of 10, 15, and 20 mg was incorporated into the HMB matrix. Physical and chemical properties, including NH3 sensitivity, of the fabricated indicators were analyzed. Results indicate that incorporation of 10 and 15 mg of BA improved the microstructure, tensile strength, transparency, and thermal stability of HMB. However, the HMB indicator with 15 mg of BA (1.5BA-HMB) exhibited better NH3 sensitivity than that of the HMB indicator with 10 mg of BA. Therefore, 15 mg was selected as the optimum concentration of BA for indicator fabrication. The 1.5BA-HMB indicator was used to monitor the freshness of mackerel (Scomber scombrus) by attaching it to inside of the package exposed to the headspace. The 1.5BA-HMB indicator clearly changed color with respect to variation in the quality of S. scombrus during storage at 4 °C. Based on the changes in the color of 1.5BA-HMB, the quality of S. scombrus was interpreted as follows: deep purple and light purple colors indicated that S. scombrus was fresh, violet color indicated that S. scombrus was suitable for eating, and blue, green ocean, and colonial blue colors indicated spoilage of S. scombrus. Thus, the 1.5BA-HMB indicator can be used as a sustainable pH-responsive indicator for intelligent food packaging.