Molecular interaction and synergistic effects of silver nanoparticles capped by thesinic acid in sodium alginate films: Toward active preservation and intelligent freshness monitoring

This study reported a multifunctional sodium alginate (SA) film enhanced with silver nanoparticles (AgNPs) for pork preservation and freshness monitoring. Spectroscopic analyses confirmed that thesinic acid (CBDA-11) served as a dual bio-reductant and capping ligand, facilitating the green synthesis of stable AgNPs. Those nanoparticles established a dense cross-linked network with the SA matrix, achieving an extraordinary tensile strength of 101 MPa while enhancing water vapor barriers and UV–vis shielding (>99.86% at 200–280 nm). The films exhibited potent antibacterial efficacy and robust antioxidant activity (84.54% ABTS scavenging). In practical applications, SA-CBDA-11-Ag films effectively retarded myoglobin oxidation, delayed protein degradation, and significantly inhibited volatile basic nitrogen accumulation and microbial proliferation, extending pork shelf life to 8 days. Furthermore, the film functioned as a colorimetric sensor, showing a pH-dependent visual transition for freshness monitoring. This work highlighted the potential of AgNPs-based films as advanced active-intelligent systems for sustainable food preservation.