Sterilization by dielectric barrier discharge low temperature plasma under different treatment conditions

Abstract:

[Objective] To study the bactericidal effect of dielectric barrier discharge low temperature plasma on Listeria monocytogenes and Salmonella Enteritidis under different treatment conditions and the content of antibacterial active substances with treatment time. [Methods] Listeria monocytogenes and Salmonella enteritidis were used as research objects to determine the total number of colonies after treatment with different voltage, time and oxygen concentration. The concentration of O₃ and NO₂ was determined by gas-active substance determination tube with treatment time and fluorescence intensity was utilized. The concentration of free radicals generated in the bacterial liquid was characterized and the changes of·OH, H₂O₂ and ¹O₂ with the treatment time were determined by fluorescence spectrophotometry. [Results] Using 70 kV, 150 s or 80 kV, 120 s could completely kill Salmonella Enteritidis, whereas Listeria monocytogenes could be completely killed only at 80 kV, 120 s. A mixture of 50% O₂+50% N₂ could completely kill the bacteria in 90 s. With the increase of treatment time, The content of intracellular ROS in two bacteria gradually increased. [Conclusion] The voltage, time and oxygen concentration could significantly enhance the bactericidal effect of plasma. Active oxygen radicals such as H₂O₂ and·OH could promote the bactericidal effect on Listeria monocytogenes and Salmonella enteritidis. Moreover, the bactericidal effect of·OH and H₂O₂ was better than that of ¹O₂.