pH-responsive halochromic films based on carboxymethyl cellulose infused with anthocyanin or curcumin dye extracts for smart packaging applications

Spoilage of food results in the formation of various compounds (amines and ammonia, among others) that affect the pH levels of the produce. Smart biodegradable packaging materials that detect food expiration by changing color based on the pH in their interior provide an eco-friendly solution to the issue of product expiration monitoring by eliminating the plastic waste otherwise generated by conventional packaging. In this study, smart packaging films were developed from a Carboxymethyl Cellulose (CMC) | Agar gel matrix infused with curcumin, red cabbage or butterfly pea flower anthocyanins. Systematic comparative tests were performed on the obtained films focusing on their thermal stability, surface and mechanical properties, Water Vapor Transmission Rate (WVTR), halochromic response, and durability to environmental exposure. The dye-infused films displayed halochromic responses with distinct sensitivities to pH levels depending on their corresponding color indicator. Finally, based on detailed colorimetric and UV–Visual spectrometric evaluations, complete mappings of the halochromic responses of the anthocyanin-infused and curcumin-infused CMC-based films, offering precise correspondences to both CIELAB color space parameters and computed RGB values of dye color changes, were compiled to serve as convenient and readily available references for researchers working on related applications.