Synthesis & characterization of κ-carrageenan/polyaniline film as intelligent food packaging

Abstract Food waste remains a significant issue globally, often driven by misinterpretation of expiration dates, resulting in the disposal of still-edible food. Intelligent food packaging offers a solution by monitoring food freshness through observable colour changes. As the freshness of protein-based foods deteriorates, gases like NH 3 will be released as a result of protein degradation, making NH 3 a reliable target analyte for monitoring food freshness. Polyaniline (PANI), with its ability to change colour based on oxidation states, offers a promising approach for freshness detection. However, its application as intelligent food packaging is restricted by poor mechanical properties and non-biodegradability. In this study, PANI synthesized via chemical oxidative polymerization was incorporated into kappa-carrageenan (κ-CGN) to enhance functionality while maintaining environmental sustainability. κ-CGN/PANI film was exposed to varying NH 3 concentrations from 200 to 1000 ppm and temperatures from −20 °C to 40 °C. A visible colour change from green to blue occurred after 45 min, measured using the RGB model of ImageJ. κ-CGN/PANI 0.50 % showed the best performance with good sensitivity (0.00005), linearity (R 2 = 0.9945), precision (RSD = 1.50 %), and LOQ (638 ppm). Long-term stability and real sample analysis showed signal ranges of 1.0620–1.0957 and 1.0151–1.0215, showcasing the potential of κ-CGN/PANI film as an effective label-form intelligent food packaging for real-time freshness monitoring.