Icariin-mediated photodynamic inactivation in antimicrobial packaging films for cherry preservation

Photodynamic antimicrobial technology based on natural functional molecules is increasingly being explored to address foodborne pathogen contamination in food preservation. Icariin (ICA), a natural bioactive flavonoid, has remained unexplored for its photodynamic potential. This study identifies ICA as a natural photosensitizer with photodynamic antibacterial activity and integrates it into active food packaging films for cherry preservation. Spectroscopic analyses confirmed the photoresponsiveness of ICA, with singlet oxygen (¹O₂) identified as the dominant reactive oxygen species. Under light irradiation, ICA achieved 99.92% inactivation of Staphylococcus aureus after 30 min and 99.96% inactivation of Listeria monocytogenes after 40 min, mainly through membrane permeabilization and intracellular leakage. To develop a safe and effective strategy for cherry preservation, ICA was incorporated into a polyvinyl alcohol/gelatin (PG) matrix to construct a photoresponsive ICA-PG film. ICA not only imparted photodynamic antibacterial activity, but also enhanced the optical, mechanical, and barrier properties of the film through hydrogen bond mediated network integration. Applied to cherries, the ICA-PG film suppressed microbial contamination, delayed softening and quality deterioration, preserved total soluble solids, pH, and firmness, and extended shelf life to 9 days. Overall, this work expands the functional scope of ICA and provides a promising route toward sustainable preservation strategies for cherries.