Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/2/2022
Publication Date: 6/4/2022
Citation: Fan, X., Vinyard, B.T., Song, Y. 2022. Cold plasma activated hydrogen peroxide aerosols inactivate Salmonella Typhimurium & Listeria innocua on smooth surfaces & stem scars of tomatoes: Modeling effects of hydrogen peroxide concentration, treatment time & dwell time. Food Control. https://doi.org/10.1016/j.foodcont.2022.109153.
Interpretive Summary: Fresh produce contaminated with foodborne human pathogens such as Listeria monocytogenes and Salmonella spp. continues to present a risk to consumers. Our previous studies demonstrated that hydrogen peroxide aerosols activated by cold plasma was more effective than hydrogen peroxide or cold plasma alone in activating bacteria on fresh produce. However, the process has not been optimized to achieve maximum efficacy against various pathogens. Experiments were undertaken to evaluate and model three parameters important for the success of the process. As a result of the present study, the conditions that attain 99.999% reductions of Listeria and Salmonella on the surface of tomatoes have been established. This information would help the produce industry apply the technology to minimize the risk of human pathogens associated with fresh produce.
Technical Abstract: This study was conducted to evaluate the effects of hydrogen peroxide (H2O2) concentration, treatment time, and dwell time on the efficacy of cold plasma-activated hydrogen peroxide aerosols against bacteria on stem scar and smooth surfaces of tomatoes. Cherry tomatoes inoculated with cocktails of Salmonella Typhimurium and Listeria innocua on the smooth surface and stem scar area were treated for 10, 20 and 30 s followed by 15 and 30 min dwell times in a treatment chamber with cold plasma-activated aerosols generated from 0, 1, 2, 3, 4 and 6% and 7.8% H2O2. Results showed that the efficacy of the treatments was mostly influenced by the H2O2 concentration and treatment time. The reductions of the two bacteria were modeled as sigmoidal or exponential functions of H2O2. The models indicated that at H2O2 concentrations = 4.2 %, the treatments reduced populations of L. innocua to non-detectable levels (detection level: 0.70 log CFU/piece) achieving an average 5 log reduction on the smooth surface of tomatoes for all tested treatment times and dwell times. To achieve an average 5-log reduction of Salmonella populations on the smooth surface, H2O2 at concentrations = 5.7% H2O2 was required. On the stem scar area of tomatoes, populations of Listeria and Salmonella were reduced by less than 2 logs. Our results demonstrated that the efficacy of cold plasma-activated hydrogen peroxide aerosol mainly depended on the concentration of H2O2, and L. innocua was more sensitive to the treatment than S. Typhimurium.