A Facile Dual‐Functional Biodegradable Silk Fibroin/Sodium Alginate Composite Film With Antibacterial Activity and pH‐Responsive Freshness Indication for Shrimp Preservation

Traditional food packaging films suffer from single function, poor fresh‐keeping performance, inability to monitor food freshness in real time and inferior biodegradability. To address these industrial bottlenecks, a multifunctional intelligent food packaging composite film was successfully fabricated based on silk fibroin‐sodium alginate (SF‐SA) matrix via the synergistic modification of zinc oxide nanoparticles/polydopamine‐modified montmorillonite (ZnO/PDA‐MMT) functional fillers and red cabbage anthocyanin (RCA). The prepared composite film possesses the advantages of pH visual responsiveness, high‐efficiency antibacterial activity and excellent biodegradability. The structural, physical, and functional performances of resultant composite films were systematically characterized. Compared with pure SF‐SA film, the introduction of ZnO/PDA‐MMT improved mechanical properties and thermal stability and reduced moisture content (MC, from 13.82 ± 1.05 to 7.31% ± 0.35%) and water vapour transmission rate (WVTR, from 964.00 ± 17.33 to 871.15 ± 35.70 g m −2 d −1 ). The composite film exhibited enhanced antioxidant capacity and favourable antibacterial activity against Escherichia coli and Staphylococcus aureus . Soil burial tests verified its desirable biodegradability with obvious structural degradation within 28 days. It displayed distinct colour transition from red to dark brown over pH 2–12, with good colour stability and ammonia‐sensing performance. Obvious colour variation occurred during shrimp spoilage, enabling real‐time visual freshness monitoring. In summary, the as‐prepared SF‐SA‐based composite film integrates superior mechanical, antibacterial, and visual indication properties, holding great application potential for aquatic product preservation and smart food packaging.