Effects of integrated treatment of nonthermal UV-C light and different antimicrobial wash on Salmonella enterica on plum tomatoes

The aim of this study was to evaluate inactivation of inoculated Salmonella enterica on whole tomato surface exploiting integration of nonthermal ultraviolet light (UV-C) treatment with antimicrobial wash. The effect of combined treatment on background microflora (aerobic mesophilic, and yeast and mold), during storage at ambient temperature (22 °C) for 21 days was also determined. A bacterial cocktail containing three serotypes of S. enterica (S. Newport H1275, S. Stanley H0558, and S. Montevideo G4639) was used based on their association with produce-related outbreaks. Tomatoes were spot inoculated using approximately 100 μL of inocula to achieve cell population of about 107 CFU/tomato. An inoculated tomato was initially treated with a low (0.6 kJ/m2) dose of UV-C light (253.7 nm) followed by immersion in selected sanitizing solution (700 ml) to wash under mild agitation (ca. 250 rpm) for 2 min at room temperature (22 °C). Inactivation efficacy of combined treatments varied widely depending on the sanitizer property. Combined UV-C plus aqueous ozone (1 ppm) provided 3.13 ± 0.47 log CFU/fruit Salmonella reduction which was significantly lower (p