An intelligent chitosan/polyvinyl alcohol film with two types of anthocyanins for improved color recognition accuracy and monitoring fresh-cut pineapple freshness

In this study, chitosan (CS), polyvinyl alcohol (PVA), and sodium tripolyphosphate (STPP) were used as bases to introduce a blend of black wolfberry (BW) and red cabbage (RC) anthocyanins. The chelation reaction of CS, PVA, and STPP resulted in the composite anthocyanins being fixed within the matrix with an appropriate ratio of composite anthocyanins stably distributed in the film. The FTIR and X-ray analyses revealed that the addition of both types of anthocyanins strengthened hydrogen bond interactions. Moreover, the CP/BR-4 film exhibited excellent antioxidant, mechanical, and antibacterial properties, as well as a sensitive and rapid response to acidic substances. The freshness of pineapples stored under refrigeration for 6 d was also evaluated, showing more significant color changes with the CP/BR-4 film than the other treatment groups. Therefore, the composite anthocyanin film can potentially serve as an intelligent film for the detection of postharvest freshness in practical applications.