Abstract
A submerged dielectric barrier discharge (DBD) plasma reactor was used to inactivate artificially inoculated reference strains of Salmonella Typhimurium ATCC 14028 on sliced onion (3 cm × 3 cm). Salmonella Typhimurium reductions obtained after 10 min of treatment were 3.96 log CFU/slice and 1.64 log CFU/slice for clean dry air and N2 feed gas, respectively. Variations observed in Optical Emission Spectra (OES) for different feed gases are responsible for the inactivation level variations of Salmonella Typhimurium. The physiochemical properties of the onion slices, such as quercetin content, ascorbic acid content and color parameters, were monitored before and after treatment and the changes that occurred were measured to be in the acceptable range. Quercetin content was reduced only 3.74–5.07% for 10 min treatment, higher reduction was obtained for the use of clean dry air than that of N2 feed gas. Ascorbic acid loss was measured to be 11.82% and 7.98% for a 10 min treatment with clean dry air and N2 feed gas, respectively. The color parameters did not show significant changes upon treatment (p > 0.05) of the same duration for the uses of different feed gases.
Highlights
A submerged dielectric barrier discharge (DBD) plasma reactor was used to inactivate artificially inoculated reference strains of Salmonella Typhimurium ATCC 14028 on sliced onion (3 cm × 3 cm)
We investigated the inactivation efficacy and mechanism for different feed gases used as well as the physiochemical quality changes of onion caused by DBD plasma discharged water treatment
Optical emission spectroscopy (OES) of the DBD plasma discharge used in this experiment shows that OH radicals and the 2nd positive system N2 (C-B) gave rise to the main peaks in the near-UV region (300–400 nm) of the Optical Emission Spectra (OES) spectrum in Fig. 1 for clean dry air gas
Summary
Optical emission spectroscopy (OES) of the DBD plasma discharge used in this experiment shows that OH radicals and the 2nd positive system N2 (C-B) gave rise to the main peaks in the near-UV region (300–400 nm) of the OES spectrum in Fig. 1 for clean dry air gas. In our previous study[25], it was observed that after 6, 4 and 8 min of plasma treatment time the amount generated for OH radical was 1.81 × 10−5 M, dissolved ozone gas was 1.5 ppm and H2O2 was 2.5 × 10−6 M, respectively. Typhimurium was 3.96 log CFU/slice onion and 1.64 log CFU/slice onion after 10 min of DBD plasma treatment inside water by clean dry air and N2 gas, respectively.
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