Inactivation of human pathogens and spoilage bacteria on the surface and internalized within fresh produce by using a combination of ultraviolet light and hydrogen peroxide

Aims: To evaluate the efficacy of ultraviolet (UV) light (254 nm) combined with hydrogen peroxide (H2O2) to inactivate bacteria on and within fresh produce. Methods and Results: The produce was steep inoculated in bacterial cell suspension followed by vacuum infiltration. The inoculated samples were sprayed with H2O2 under constant UV illumination. The log count reduction (LCR) of Salmonella on and within lettuce was dependent on the H2O2 concentration, temperature and treatment time with UV intensity being less significant. By using the optimized parameters (1.5% H2O2 at 50 degrees C, UV dose of 37.8 mJ cm(-2)), the surface Salmonella were reduced by 4.12 +/- 0.45 and internal counts by 2.84 +/- 0.34 log CFU, which was significantly higher compared with H2O2 or UV alone. Higher LCR of Escherichia coli O157:H7, Pectobacterium carotovora, Pseudomonas fluorescens and Salmonella were achieved on leafy vegetables compared with produce, such as cauliflower. In all cases, the surface LCR were significantly higher compared with the samples treated with 200 ppm hypochlorite. UV-H2O2-treated lettuce did not develop brown discolouration during storage but growth of residual survivors occurred with samples held at 25 degrees C. Conclusions: UV-H2O2 reduce the bacterial populations on and within fresh produce without affecting the shelf-life stability. Significance of the Study: UV-H2O2 represent an alternative to hypochlorite washes to decontaminate fresh produce.