Inactivation of Listeria monocytogenes on post-harvest carrot and tomato by gamma radiation, sanitizer, biocontrol treatments and their combinations

Control of foodborne pathogens on post-harvest produce may be improved by combined treatments. Hurdle applications may enhance the lethal effects of non-thermal interventions on pathogenic bacteria. We evaluated the effects of gamma radiation (0.5 kGy), nisin-based sanitizer (100%), and competitive biocontrol microbes (non-pathogenic Pseudomorias fluorescens) on the survival of Listeria monocytogenes on post-harvest tomato and carrot. Produce storage temperatures (5 and 20 degrees C) and days (0 and 7), with single, two or three treatment combinations of radiation (R), sanitizer (S) and biocontrol (B) were investigated for pathogen survival. Significant differences (P < 0.05) in L. monocytogenes and subsequent pathogen reductions on produce by hurdle treatments were recorded. L monocytogenes reductions on carrot and tomato varied, as R + S + B and S R + B hurdle treatments (day 7) reduced Listeria survival by 2.5-5.0 and 2.4-5.0 log CFU/g of produce, respectively, at both temperatures. The sanitizer (S) treatment reduced Listeria on produce by 2.2-4.7 logs (day 7), while R or B treatments also reduced Listeria survival on produce. The treatment efficacies on pathogen survival were sanitizer > radiation > biocontrol. Inactivation of Lister/a on post-harvest produce may be improved by treatment combinations as hurdle applications could enhance the safety of post-harvest carrot and tomato.