Moisture vaporization-combined helium dielectric barrier discharge-cold plasma treatment for microbial decontamination of onion flakes

Abstract

The effects of treatment frequency and time on the inactivation of Salmonella enterica serovar Enteritidis, Escherichia coli O157:H7, and Listeria monocytogenes on onion (Allium cepa L.) flakes were investigated using dielectric barrier discharge-cold plasma (DBD-CP) treatment combined with moisture vaporization, while optimizing the treatment conditions against microbial inactivation and studying the inactivation kinetic models. Onion flakes were subjected to CP treatment using helium for 2–20 min at 15–35 kHz. The microbial reduction decreased with treatment frequency and increased with time (P < 0.05). CP treatment at 15 kHz for 20 min resulted in the highest reduction of S. Enteritidis, E. coli O157:H7, and L. monocytogenes (3.1 ± 0.1, 1.4 ± 0.1, and 1.1 ± 0.3 log CFU/cm2, respectively), with a temperature increase of 14.6 °C from 25.0 °C. Among the first-order, Fermi, and Weibull models, the Fermi model adequately explained the microbial inactivation of all tested pathogens by CP treatment (R2: 0.84–0.94). Moisture vaporization into plasma-forming gas increased the concentrations of reactive oxygen species and hydrogen in He-CP. The optimal CP treatment at 15 kHz for 20 min did not significantly affect the surface morphology; color; or moisture, ascorbic acid, and quercetin contents of onion flakes (P > 0.05). CP treatment combined with moisture vaporization effectively inactivated the foodborne pathogens contaminating onion flakes, without altering the physicochemical properties of the food product.