A cost-effective low-frequency powered plasma ozonation system for postharvest microbial control under vacuum condition

Growing demand for minimally processed foods requires preservation technologies that improve microbial safety without causing thermal damage or leaving chemical residues. Among these, plasma-based technologies are emerging as promising non-thermal approaches for extending the shelf-life of fruits and vegetables. In this study, we report the development of an in-house plasma ozonator powered by a standard 50 Hz household alternating current supply, designed as a cost-effective and accessible alternative to complex plasma systems. The oxygen plasma discharge in the reactor generates a variety of reactive species, including atomic and ionic oxygen, which subsequently recombine to form ozone—a potent antimicrobial agent. An electrochemical ozone sensor was utilized for the direct measurement of ozone concentration in the vacuum chamber. The finding reveals that the ozone concentration increased from 0.38 to 0.43 ppm with an increase in gas pressure at a fixed flow rate of 30 sccm. Plasma-ozone treatment (10- and 20-min exposure) demonstrated significant reductions in microbial contamination in comparison to untreated samples. These findings confirm that plasma ozone technology effectively enhances the shelf-life and microbial safety of fresh produce without compromising nutritional quality. This research contributes to sustainable food preservation strategies by demonstrating an environmentally friendly and economically viable plasma-based solution for postharvest treatment.