Development of a UV-cured intelligent film based on sodium alginate/polyvinyl alcohol, Nano-TiO₂, and anthocyanins extracted from purple Asparagus for Salmon freshness assessment

In this study, an intelligent indicator film was developed through a photocatalytic process. The film was fabricated using a natural biopolymer matrix composed of sodium alginate and polyvinyl alcohol, into which purple asparagus anthocyanins and nano-scale titanium dioxide were incorporated. Following sufficient ultraviolet light (245 nm) irradiation to activate the titanium dioxide catalyst, the resultant solution was cast to form the film. Crucially, this tailored UV exposure simultaneously photo-activates TiO 2 and induces in-situ cross-linking within the sodium alginate/polyvinyl alcohol (SA/PVA) network, providing a novel non-thermal structuring step that distinguishes the present system from previously reported indicator films. Scanning electron microscopy and atomic force microscopy images showed that the addition of anthocyanins and titanium dioxide nanoparticles caused the film surface to become rough and porous. The photocatalyzed composite films significantly reduced moisture content and water vapor permeability. The ultraviolet light treated polymer (UV-SPTA) films exhibited enhanced mechanical strength, antimicrobial and antioxidant properties, as well as high sensitivity and rapid response to alkalinity compared to other treatment groups. In addition, the UV-SPTA film enhanced the freshness of salmon stored under refrigeration for 84 h by significantly inhibiting microbial growth and spoilage of flavor substances, with a more pronounced color change than in the other treatment groups. • A smart color-changing film containing purple asparagus anthocyanins. • Photocatalyzed titanium dioxide has enhanced antibacterial properties. • Intelligent film indicates freshness while extending storage • Combine Clean Energy and Smart Materials to Extend Shelf Life.