Moldgy, Ankit2020-09-082020-09-082020-06https://hdl.handle.net/11299/216065University of Minnesota M.S. thesis. June 2019. Major: Mechanical Engineering. Advisor: Peter Bruggeman. 1 computer file (PDF); xi, 94 pages.Cold atmospheric pressure plasmas are being widely studied for applications in biology and medicine. Non-thermal plasma-based decontamination has been one of the important areas of investigation due to the capability of cold plasmas to generate reactive species with antimicrobial properties close to room temperatures. Foodborne viruses and bacteria have been major causes of disease outbreaks, especially through the consumption of minimally processed foods and fresh produce. Conventional non-thermal food processing technologies face limitations and affect the properties of food. This work on plasma-based decontamination was motivated by the necessity to develop an effective and efficient non-thermal food decontamination technology. We used different plasma sources operating in air at atmospheric pressure for surface decontamination experiments. These experiments were performed with feline calicivirus (FCV), a surrogate of human norovirus, and Salmonella Heidelberg on stainless steel discs as model for food contact surfaces. The substrates were treated in dry and wet surface conditions. The plasma sources were designed such that the substrates are treated either directly such that there is direct contact between the plasma and the substrate or remotely such that the reactive species in the afterglow are transported to the substrate. It was shown that humidity on the surface of the substrate strongly enhances the decontamination effectiveness. Only direct treatment was seen to be significantly effective against dry samples. All the plasma sources achieve complete inactivation of wet samples. Synergistic effects between O3 and NO2 in the afterglow of the DBDs was recognized through positive control tests. With the use of a kinetic model to study the interaction among the chemical species in the afterglow of the plasma, the virucidal effects induced by the DBDs were attributed to the generation of gas-phase N2O5. The influence of surface humidity was studied through the quantification of reactive species in the water layer covering the substrate. It was found that the reactive species concentrations increased as the volume of the water decreased and this effect was consistent with the observed decontamination effects. The importance of enhancing the transport of reactive species from the gas to liquid phase for optimal decontamination efficacy of remote plasma treatment was identified. Finally, plasma sources were compared based on the energy consumption requirements for achieving complete decontamination. To gain an understanding on the possibilities of adoption of plasma technologies by the food industry, the plasma sources were compared with UV-C radiation in terms of energy costs and practical utility. For surface decontamination, direct plasma treatment was found to be four times more energy-intensive than UV-C treatment. A significant enhancement of energy efficiency was achieved using remote plasma treatment in a lab-scale batch reactor prototype employing a surface discharge generating predominantly O3, leading to energy per unit area requirements similar to that for UV-C. Preliminary estimates suggest that the energy efficiency might be further increased for a source enabling disinfection by reactive nitrogen species.enThesis or Dissertation