pH ‐Driven Gelatin/γ‐ PGA /Alizarin Smart Films for Real‐Time Seafood Freshness Monitoring

To address the growing demand for fresh‐keeping and real‐time food freshness monitoring, a multifunctional intelligent packaging film was developed based on a gelatin/γ‐polyglutamic acid (γ‐PGA) composite reinforced with polydextrose and alizarin via a pH‐driven method. Systematic investigations confirmed that setting the pH of the film‐forming solution to 3 promoted the most intense electrostatic interactions and hydrogen bonding between the biopolymers. This optimal condition facilitated the establishment of a compact and robust network architecture, significantly enhancing the physicochemical properties. Compared to pure gelatin films, the optimized film (pH 3) exhibited a 4.3‐fold increase in tensile strength (38.8 MPa), a 45% reduction in water vapor permeability, and a 62% reduction in oxygen permeability. In preservation tests, the film extended the shelf life of shrimp by approximately 2 days at 4°C. Crucially, quantitative analysis demonstrated significant linear correlations between film color parameters (Δ E and S RGB ) and food freshness indicators (TVB‐N and pH). This research provides a theoretical foundation and a viable technical pathway for developing high‐performance, visually interpretable intelligent packaging materials that successfully integrate mechanical durability with reliable freshness monitoring for perishable food products.