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

- This is the first study to use a cold plasma system developed for flake treatment.
- Vaporization-integrated treatment inactivated pathogens on onion flakes well.
- The treatment resulted in the highest reduction of tested pathogens at 15 kHz.
- Fermi's model adequately explained the microbial inactivation of tested pathogens.
- The optimal treatment did not alter the physicochemical properties of onion flakes.

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.