Impact of low‐dose gaseous ozone treatment to reduce the growth of in vitro broth cultures of foodborne pathogenic/spoilage bacteria in a food storage cold chamber

Cold storage coupled with gaseous ozone represents a potential strategy to reduce or inhibit the presence of pathogenic and spoilage bacteria in a food storage cold chamber. This study aims to evaluate the impact of gaseous ozone treatment (0.05 ppm at exposure times of 30 and 60 min) on the bacterial contamination of internal surface and air in a cold chamber (3C) intended for food storage. The bacterial load of internal surfaces was reduced by 0.99 ± 0.24 and 1.35 ± 0.27 log after 30 and 60 min ozone treatment, respectively. Airborne bacterial load was reduced by 0.93 ± 0.24 log after 30 min ozone treatment and became non-detectable after 60 min. Gaseous ozone treatments (0.05 ppm at exposure times of 1, 2, 6, 24, 30, and 48 hr) of the cold chamber were investigated to evaluate the effectiveness of this technology against Escherichia coli, Listeria monocytogenes, Salmonella enterica Typhimurium, Campylobacter jejuni, and Pseudomonas fluorescens cultured in broth cultures. Ozone treatment was effective against C. jejuni since the population at the highest concentration of inoculum (3.34 log CFU/plate) was reduced by 2.23 log after 1 hr and it was completely undetectable after 2 hr. S. enterica and E. coli showed the highest resistance to short ozone treatment since 6 hr treatment did not show antibacterial activity whereas after 24 hr treatment around 2 log reduction was observed for both pathogens. Short ozone treatment did not affect L. monocytogenes viability. P. fluorescens showed high sensitivity to short treatments, with 0.75–1.32 log reductions after 1 hr and further 0.22–0.53 log reductions after 6 hr.