Intelligent pH-responsive films based on natural blueberry anthocyanins: A non-destructive monitoring system for the freshness of aquatic products with prospective smartphone compatibility

Packaging plays a pivotal role in preserving food quality throughout processing and storage. This study developed a smart hydroxypropyl methylcellulose- κ-carrageenan- gelatin (H-K-G-B) film containing blueberry anthocyanins (BA) for freshness monitoring. The incorporation of BA significantly enhanced the film's antioxidant properties, with DPPH and ABTS radical scavenging capacities reaching 82.92 % and 86.44 %, respectively. The mechanical strength of H-K-G-B film was satisfactory, achieving tensile strength of 5.85 MPa and Young's modulus of 24.05 MPa, along with superior UV–vis light barrier performance. The H-K-G-B film exhibited high NH₃ sensitivity at 32.79 % and distinct color changes with pH response in alkaline environments (R² = 0.9502), which was successfully applied in salmon spoilage indication. Moreover, based on the significantly correlations (R² > 0.90) between chromatic parameters and quality parameters, including pH, TVB-N, and TBARS, a smartphone-based visual detection platform for real-time food freshness indication was established. So, this work provides a scientifically validated solution for intelligent food packaging.