123: Sustainable photoactive food packaging. Structural and optical characterization

Abstract: The development of sustainable food packaging materials with active preservation functions represents a key challenge for green chemistry and circular bioeconomy strategies. In this work, biodegradable photoactive films based on sodium alginate were designed and characterized as potential antimicrobial and antioxidant packaging systems. Natural and food-grade photosensitizers—curcumin, rose bengal, and riboflavin—were incorporated into the polymer matrix to provide light-responsive functionality while maintaining a fully biobased formulation. The structural and physicochemical properties of the films were investigated using complementary techniques. Surface morphology and microstructure were analyzed by scanning electron microscopy (SEM) and atomic force microscopy (AFM), revealing homogeneous matrices with photosensitizer-dependent textural features. Chemical interactions between alginate and the active compounds were evaluated through Fourier transform infrared spectroscopy (FTIR), confirming successful incorporation without major alteration of the polymer backbone. Steady-state fluorescence spectroscopy was employed to assess optical behavior, molecular distribution, and potential aggregation phenomena within the films. The results demonstrate that the selected photosensitizers can be effectively immobilized in alginate matrices, generating stable materials with tunable optical properties. These findings highlight the potential of naturally derived, light-activated packaging systems as environmentally friendly alternatives to conventional synthetic preservatives, contributing to safer and more sustainable strategies for food preservation.