Cold plasma-activated hydrogen peroxide aerosols inactivate Salmonella Typhimurium and Listeria innocua on smooth surfaces and stem scars of tomatoes: Modeling effects of hydrogen peroxide concentration, treatment time and dwell time
2022
Fan, Xuetong | Vinyard, Bryan T. | Song, Yuanyuan
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 type and location of inoculated bacteria.
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