Barley sprouts are 5 to 20 day-old grown whole plants that are widely consumed as a functional vegetable due to their health-promoting compounds such as saponarin, γ -Aminobutyric acid (GABA), and policosanols. Recent plasma applications have been a promising approach in the agricultural and food industries to produce bioactive phytochemicals in sprouted crops. Therefore, this study investigated the plasma effects on the whole plant and its bioactive phytochemicals compared with those of an untreated control in barley sprouts. The optimal plasma exposure during seed germination can change physical and chemical properties of fully hydrated seeds of barley, accelerate the early growth of its sprouts and enhance bioactive phytochemicals in the sprouts. Thus, a single 6 min exposure of the plasma enhanced the fresh weight of whole barley seedlings by 137.5% of the untreated control at 9 d after the exposure and enhanced the contents of the primary metabolites including soluble sugars and free amino acids, and secondary metabolites including special phytochemicals such as saponarin, GABA, and policosanols. Therefore, our results suggest that the optimal plasma exposure can be used as a promising seed priming technique for the whole plant and the bioactive phytochemicals of barley sprouts.

In this study, we investigated the antimicrobial effects of plasma activated fine droplet (PAD) produced from arc discharge plasma on planktonic Listeria monocytogenes and Escherichia coli O157:H7. NaCl (0.9%, w/v) was used as the feeding solution for the plasma discharge. The inactivation mechanism of the PAD treatment was also investigated. PAD mainly contains H ₂ O ₂ and OCl ⁻ , which play a significant role in the inactivation process against L. monocytogenes and E. coli O157:H7. The population of L. monocytogenes and E. coli O157:H7 was significantly reduced by approximately 3 and 4 log units, respectively, within 5 min of exposure to PAD. However, the bactericidal effects of PAD against L. monocytogenes and E. coli O157:H7 showed different trends by showing 0.58 and 4.13 log reductions, respectively, after 1 min of PAD exposure time. The change of membrane integrity was evaluated using two DNA-binding fluorescence dyes, SYTO 9 and propidium iodide (PI). The breakage of the cell wall and membrane of both microorganisms was evidenced by the uptake of PI by cells after 5 min of exposure to PAD, but the effect was less in L. monocytogenes compared to E. coli O157:H7 after 1 min of PAD exposure time. The transmission electron microscopy results clearly showed morphological changes in both microorganisms, including denaturation or leakage of intracellular materials as a consequence of PAD treatment. These findings suggest that PAD-induced chemical species can eventually affect the intracellular materials of bacterial cells by passing through or attacking the cell envelope. In addition, L. monocytogenes are less susceptible to PAD compared with E. coli O157:H7.

The key reactive species generated by non-thermal plasma bubbles for the inactivation of Salmonella Typhimurium and the effects of organic matter on the inactivation efficacy were investigated. Plasma, which is primarily composed of ozone (O₃), was generated by dielectric barrier discharge and injected into a solution (400 mL) as a bubble. The surviving population of S. Typhimurium decreased in proportion to the treatment time, resulting in a 5.29 log reduction after 5 min of treatment. Verification tests to specify key reactive species were conducted using an O₃ destruction unit and reactive oxygen species scavengers. The results indicated that singlet oxygen (¹O₂) contributes substantially to the inactivation of S. Typhimurium, and that the presence of superoxide anion radicals (O₂^·−) from O₃ is essential for the production of ¹O₂. When a S. Typhimurium suspension containing organic matter (final concentration: 0, 0.005, 0.05, 0.1, and 0.5 g/L), consisting of beef extract and peptone, was treated with plasma bubbles for 5, 10, 15, 20, 25, and 30 min, respectively, the potential of the plasma bubbles for inactivating S. Typhimurium successfully was verified with longer contact time, despite organic matter attenuating the inactivation efficiency in a dose-dependent manner.

Hydrodynamic cavitation (HC) and Fe(II) are advanced oxidation processes, in which pentachlorophenol (PCP) is treated by the redox method of activating persulfate (PS). The kinetics and mechanism of the HC and Fe(II) activation of PS were examined in aqueous solution using an electron spin resonance (ESR) spin trapping technique and radical trapping with pure compounds. The optimum ratio of Fe(II)/PS was 1:2, and the hydroxyl radical (HO) and sulfate radical (SO4-) generation rate were 5.56 mM h-1 and 8.62 μM h-1, respectively. The generation rate and Rct of HO and SO4- at pH 3 and 50 °C in the Fe(II)/PS/HC system are 7584.6 μM h-1, 0.013 and 24.02 μM h-1, 3.95, respectively. The number of radicals was reduced as the pH increased, and it increased with increasing temperature. The PCP reaction rate constants was 4.39 × 10-2 min-1 at pH 3 and 50 °C. The activation energy was 10.68 kJ mol-1. In addition, the mechanism of PCP treatment in the Fe(II)/PS/HC system was a redox reaction, and the HO-/SO4- contribution was 81.1 and 18.9%, respectively. In this study, we first examined PCP oxidation through HO and SO4- quantification using only the Fe(II)/PS/HC process. Furthermore, the results provide the foundation for activation of PS by HC and Fe(II), but also provide a data basis for similar organic treatments other than PCP.