Propyl gallate-mediated photodynamic inactivation: Mechanistic insights and applications for grass carp fish...

Propyl gallate (PG), a common food antioxidant, has demonstrated remarkable potential as a photosensitizer for antimicrobial photodynamic inactivation under UV-A irradiation. Against Pseudomonas fluorescens, PG-mediated treatment achieved an exceptional bacterial reduction exceeding 7 log CFU/mL. Mechanistic studies revealed extensive cellular damage through DNA degradation and protein denaturation, as visualized via electron microscopy, showing compromised membrane integrity. Antimicrobial action proceeded through the generation of OH-radicals, H₂O₂, and superoxide (O₂•^-), with intracellular reactive oxygen species accumulation confirmed by confocal microscopy. Beyond in-vitro grass carp fillet applications, PG-mediated reduced bacterial contamination by 3.5 log CFU/g while preserving food quality. PG-mediated based samples exhibited 47% lower lipid oxidation, 33% higher sulfhydryl content retention, and 29% reduction in total volatile basic nitrogen compared to the control ones. Additionally, the pH stability and color parameters remained consistent throughout storage. These findings establish PG-mediated photodynamic treatment as a combined antimicrobial and antioxidant functionality, simultaneously ensuring microbial safety and maintaining nutritional quality in seafood preservation.