Curcumin/octyl gallate/chitosan photodynamic coating with enhanced adhesion and antibacterial efficacy for preservation of prepared mutton

Photodynamic inactivation (PDI) is a promising non-thermal antimicrobial technology. However, its practical application is constrained by the low-light utilization efficiency and poor adhesion of photosensitizers. To address these limitations, we developed a curcumin/octyl gallate/chitosan (COS) coating. COS was prepared via a two-stage self-assembly process by incorporating a curcumin/octyl gallate (CUR/OG) assembly into a chitosan (CS) matrix. The CUR/OG, characterized by a band gap of 2.3 eV, imparted visible-light activity to the COS. Furthermore, the COS exhibited good adhesion, storage stability, and photostability. Compared to pristine CS, the COS exhibited a 1.3-fold enhancement in adhesion strength. Upon visible-light irradiation, it achieved up to a 6.5-log CFU reduction in the population of four representative foodborne bacteria ( Pseudomonas fragi , Brochothrix thermosphacta , Escherichia coli O157:H7, and Staphylococcus aureus ). Biochemical analyses indicated that COS-mediated PDI was associated with the disruption of bacterial cell membrane integrity, impairment of energy metabolism, and induction of oxidative stress. Under visible light, the COS extended the refrigerated shelf-life of prepared mutton to 1.5 times that of the untreated control. Moreover, the COS-mediated PDI maintained approximately 99.99% reduction in bacterial counts after three consecutive reuse cycles on food contact surfaces. This study provided an effective approach for enhancing the bactericidal activity and adhesion of photodynamic coatings, offering a promising solution for preservation of prepared mutton.