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

Abstract

This study was conducted to evaluate the effects of hydrogen peroxide (H 2 O 2 ) 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% H 2 O 2 . Results showed that the efficacy of the treatments was mostly influenced by the H 2 O 2 concentration and treatment time. The reductions of the two bacteria were modeled as sigmoidal or exponential functions of H 2 O 2 . The models indicated that at H 2 O 2 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, H 2 O 2 at concentrations ≥5.7% H 2 O 2 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 H 2 O 2 , and type and location of inoculated bacteria. • Three main parameters for cold plasma-activated H 2 O 2 process were evaluated. • Non-linear regression models were developed for estimating the efficacy of H 2 O 2 . • Listeria was more sensitive to the activated H 2 O 2 aerosol than Salmonella on tomatoes. • At ≥5.7% H 2 O 2 , both bacteria on the surface of tomatoes were reduced by 5 logs. • Bacteria on stem scar area were more difficult to inactivate than those on surface.