Enhancement of curcumin-mediated photodynamic inactivation against Pseudomonas fluorescens on fish fillets combined with ε-polylysine hydrochloride

The application of curcumin-mediated photodynamic inactivation (Cur-PDI) remains challenging in controlling food microbial contamination for the poor aqueous solubility and bioavailability of Cur. This study aimed to evaluate the bactericidal effect of Cur-PDI combined with ε-polylysine hydrochloride (ε-PLH) on Pseudomonas fluorescens and its preservation effect on large yellow croaker using microbial indicators and physicochemical indicators such as total volatile basic nitrogen (TVB), pH value and color difference. After treatment of 45 μM Cur-PDI (60.97 J/cm 2 , 430 nm) combined with 100 μg/mL ε-PLH, the population of P. fluorescens PF07 were reduced by 6.36 log CFU/mL, and the stronger reactive oxygen species were produced in combination than single PDI, resulting in the significant damage of intracellular enzymes and DNA. Meanwhile, the combined PDI decreased initial total viable count and Pseudomonas population of large yellow croaker, and apparently inhibited their growth. Compared with the control, TVB production was restrained, and the alteration of in pH value, total color and sensory scores in combination were significantly delayed, extending the shelf life for 2 d at 4°C. Our findings would contribute to elucidating the bactericidal mechanism of PDI combined with ε-PLH and application in aquatic products preservation. • Cur-PDI combined with ε-PLH reduced P. fluorescens in vitro by 6.36 log CFU/mL. • ε-PLH improved the penetration of Cur increasing inactivation efficacy of Cur-PDI. • Excessive formation of ROS damaged cell structure as vital bactericidal mechanisms. • Combined PDI effectively extended the shelf life of fish fillet for 2 days.