Development of sodium alginate-titanium dioxide films incorporating anthocyanin for antibacterial and freshness sensing applications

To address food waste and commercial plastic pollution at the consumer level, we developed UV-catalyzed active films by blending sodium alginate (SA), titanium dioxide nanoparticles (TiO₂), and red kale extract (RKE; Brassica oleracea var. sabellica). The solution was prepared and subjected to UV irradiation and finally cast into films. Mechanical properties revealed that UV films exhibited a 47 % increase in elongation at break, while water vapor permeability decreased by 41 %. When applied to cold-stored shrimp (4 °C, 84 h), the UV-activated films extended the detectable freshness period by approximately 36 h compared to non-activated control (SA), as evidenced by delayed volatile base nitrogen (TVB-N) accumulation (threshold reached at 84 h vs. 72 h) and pH evaluation. Real-time pH-dependent color shifts-transitioning from purple, lake blue to green between pH 6.5 and 9.3-allowed clear differentiation of fresh, sub-fresh, and spoiled stages. This study introduces a promising strategy for real-time freshness monitoring, offering new opportunities for differentiated food quality assessment.