Modelling of Inactivation Kinetics of Escherichia coli on Radish and Hemp seeds and Their Physicochemical Properties after Non-Thermal Plasma Treatment: A Comparative Study of Two Plasma Sources

In recent years, seed sprout consumption has been associated with several infectious outbreaks. To ensure sprouts are safe to eat, any potential pathogens must be eliminated before the sprouting process begins. The objective of this study was to compare the efficacy of two different plasma sources, producing non-thermal plasma under ambient air conditions, on the inactivation kinetics of Escherichia coli on radish and hemp seeds intended for sprouting. Plasma treatments were conducted using Diffuse Coplanar Surface Barrier Discharge (DCSBD) and piezoelectric direct discharge plasma called the Piezobrush PZ3. Microbial inactivation data were modelled using the Bigelow log-linear, biphasic, and Weibull models. After 90 seconds of DCSBD plasma treatment, reductions of 4.79 log10 CFU/g in radish seeds and 5.27 log10 CFU/g in hemp seeds were achieved. The inactivation effect of Piezobrush PZ3 was less effective in comparison to DCSBD and more pronounced against E. coli on hemp seeds than on radish seeds. Plasma treatments enhanced the physicochemical properties of seeds without causing significant changes to their surface morphology. Treatment with both plasma sources led to enhanced wettability in both seed types and an increase in soluble protein content in radish seeds. In the treatment with Piezobrush PZ3, reducing sugar content in both seed types increased up to 180 seconds of plasma exposure; however, prolonged exposure resulted in a subsequent decrease. Non-thermal plasma is a promising technology for the decontamination of seeds intended for sprouting; however, selecting the appropriate plasma discharge is crucial.