The optimization of plasma activated water ( PAW ) generation and the inactivation mechanism of PAW on Escherichia coli

Abstract

Plasma activated water (PAW) generated by nonthermal plasma, an acidified solution containing a variety of reactive species, has become a new decontamination approach because of its bactericidal ability. This study investigated the effects of various generation conditions of PAW on bactericidal activities against Escherichia coli and its physicochemical properties. PAW was prepared by ultrapure water with dielectric barrier discharge (DBD) plasma. The optimal generation condition of PAW was 30 min plasma activation time, 20 ml solution volume, 15.2 kV input voltage, and 5.5 kHz frequency operation. Under various mimicked liquid analytics, nitrate, nitrite, superoxide anion radicals, and strong acidification play significant roles in the antimicrobial properties of PAW. Therefore, these findings provide a basis for the PAW inactivation mechanism, and PAW can be a promising alternative to traditional sanitizers for food safety and preservation. Practical applications Plasma‐activated water (PAW) is an emerging non‐thermal technology that could be applied in the food industry. The liquid creates an acidic environment which results in changes of the redox potential, conductivity, and the formation of reactive oxygen and nitrogen species. As a result, PAW has different chemical composition than water and can serve as an alternative method for microbial disinfection. This study presents physicochemical properties and bactericidal effects of PAW under different generation conditions. Moreover, the inactivation mechanism of Escherichia coli by PAW was analyzed using various mimicked solutions. This investigation will help to have a better understanding of PAW technology and extend the potential applications in the agri‐food industry in the future.

A review on plasma‐activated water and its application in the meat industry

“…However, few researchers have proposed that the ROS in PAW are also responsible for the microbial inactivation of PAW by initiating lipid peroxidation in the cell membrane (Gan et al, 2022;Perinban et al, 2022). Han et al (2022) reported that •O 2 − has a key role in the mechanism of antimicrobial inactivation induced by PAW while NO − 2 and NO − 3 with pH drop acted as the supporting agents in the inactivation. •OH also plays a role in the bacterial inactivation by oxidizing unsaturated fatty acids in the cell membrane, cleaving peptide bonds, and oxidizing amino acid side chains (Guo et al, 2023).…”

“…In addition, the storage temperature of 4 • C maintained the inactivation efficacy of PAW higher than at 22 • C (Wang & Salvi, 2021). Han et al (2022) evaluated the influence of storage times at 7.5, 15, 30, and 60 min at room temperature during the PAW inactivation efficacy against planktonic E. coli. The authors reported that more than 6.18 log 10 reduction CFU.mL −1 of PAW was achieved with the storage time of 7.5 min (Figure 7).…”

“…Han et al. (2022) reported that ∙O 2 − has a key role in the mechanism of antimicrobial inactivation induced by PAW while $${\mathrm{NO}}_2^ - $$ and $${\mathrm{NO}}_3^ - $$ with pH drop acted as the supporting agents in the inactivation. ∙OH also plays a role in the bacterial inactivation by oxidizing unsaturated fatty acids in the cell membrane, cleaving peptide bonds, and oxidizing amino acid side chains (Guo et al., 2023).…”

“…The authors reported that more than 6.18 log 10 reduction CFU.mL −1 of PAW was achieved with the storage time of 7.5 min (Figure 7). However, when the storage time reached 30 min, the inactivation decreased (Figure 7), which was attributed to the decrease of superoxide anion radicals as they are important inactivation agents in PAW (Han et al., 2022).…”