Electrolyzed Water

As one of the most promising sterilization agents for microbial control in food industry in recent decades, electrolyzed water (EW) can be produced from diluted NaCl solution, and exhibits strong broad-spectrum bactericidal efficiency due to the synergistic effect of available chlorine concentrations, pH and oxidation reduction potential. To date, numerous studies have demonstrated the antimicrobial activity of EW against various kinds of microorganisms both in vitro and in vivo. However, the exact antimicrobial mechanisms of EW have not been determined at present, limiting its widespread application. In this review, we provide an overview of latest production equipment of EW, and briefly summarize the current advances of germicidal factors and antimicrobial mechanisms of electrolyzed water on different states of microorganisms. In addition, studies about hurdle enhancement of EW combined with other technologies are also discussed, providing guidelines for improving food safety and food quality both in conventional and organic food industry.

A novel method was used to produce near neutral pH electrolysed water (NEW) by developing a portable electrochemical sanitising unit that uses diluted sodium chloride and sodium bicarbonate solution (6 mM) as electrolytes. The unit produced NEW at pH 5.70 to 7.1, an oxidation-reduction potential of 802.2-933.8 mV, and free available chlorine (FAC) of 3.3-70 mg/L. NEW produced by the unit with NaCl 10 g/L showed stronger bactericidal effects than NEW produced by mixing the anode and cathode product from commercial unit's (P < 0.05): 2.03 log colony forming units (CFU)/mL reductions compared with 1.66 log CFU/mL reductions. To further understand the sanitising result, electron spin resonance and flow cytometry were performed. The results showed NEW produced by the developed unit induced 82.2% injured cells compared with 54.4% by NEW without detected free radicals. Overall, the current efficiency and power consumption were increased during NEW generation for NEW using sodium bicarbonate compared with sole NEW. The developed NEW generator is a promising sanitising unit for consumers and food industry to control foodborne pathogens.

To maintain the quality and shelf life of cherry tomatoes, microbial decontamination is essential. The objective of this study was to determine the effect of acidic electrolyzed water (AcEW), hydrogen peroxide (H2O2), ozone water (O3) and sodium hypochlorite (NaClO) on quality, shelf life and microbial decontamination of cherry tomatoes. Water was used as control. AcEW, H2O2, O3 and NaClO were sprayed one day prior to harvest. Afterwards, tomato fruits were stored at 5 ˚C to determine their quality, shelf life and microbial activity. Respiration (p ≤ 0.001) and ethylene production (p ≤ 0.01) were significantly lower in O3-treated tomato fruits compared to those in other treatments. The lowest fresh weight loss and the longest shelf life 20 days (p ≤ 0.05) were found for O3-treated tomato fruits. Their fungal incidence rate (p ≤ 0.001) and microbial activity were the lowest. However, fruits firmness 13.36N (p ≤ 0.01) was significantly retained for O3-treated tomato fruits. Color development, lycopene content and fructose and glucose contents suppressed by O3-treatment might have prolonged the shelf life of tomato fruits. Based on comprehensive results of physiological, physicochemical and microbiological analysis, O3-treated tomato fruits prolonged shelf life and maintained their quality at 5˚C. Therefore, O3-treatment might have great potential to be used for long time storage of cherry tomatoes.

Meat and seafood products present a viable medium for microbial propagation, which contributes to foodborne illnesses and quality losses. The development of novel and effective techniques for microbial decontamination is therefore vital to the food industry. Water presents a unique advantage for large-scale applications, which can be functionalized to inactivate microbial growth, ensuring the safety and quality of meat and seafood products. By taking into account the increased popularity of functionalized water utilization through electrolysis, ozonation and cold plasma technology, relevant literature regarding their applications in meat and seafood safety and quality are reviewed. In addition, the principles of generating functionalized water are presented, and the safety issues associated with their uses are also discussed.

Functionalization of water is a promising approach for the microbiological safety and quality of meat and seafood products and possesses synergistic effects when combined with other decontamination approaches. However, functionalized water is often misused since the active antimicrobial component is applied at a much higher concentration, despite the availability of applicable regulations. Functionalized water also shows reduced antimicrobial efficiency and may produce disinfection by-products (DBPs) in the presence of organic matter, especially at a higher concentration of active microbial component. Utilization should be encouraged within regulated guidelines, especially as hurdle technology, while plasma functionalized water which emerges with great potentials should be exploited for future applications. It is hoped that this review should encourage the industry to adopt the functionalized water as an effective alternative technique for the food industry.

To determine the bactericidal mechanism of electrolyzed water and mild heat against Escherichia coli O157:H7, we performed ultra-performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-qTOF-MS/MS) coupled with multivariate analysis to profile the intracellular metabolites of E. coli O157:H7 in response to electrolyzed water (EW) and mild heat treatment. The results indicated that EW (4 mg/L free available chlorine) combined with heat treatment at 50°C resulted in 2.31 log CFU/mL reduction of E. coli O157:H7 and the reactive oxygen species fluorescence intensity of EW at 50°C was ten times higher than that of the control group. Data demonstrated that treatment with EW and heat caused significant perturbation of metabolic pathways that were functionally related with amino acid metabolism, nucleotides synthesis, and lipid biosynthesis. EW at 50°C resulted in major alterations to pathways involved in acyl carrier protein metabolism, anhydromuropeptides recycling, biosynthesis of CDP-diacylglycerol, trehalose and lipid IVa. Transcriptome analysis revealed that heat and EW affected the transcription levels of some genes in opposite ways. The expression of rpoS, oxyR, soxR, gadA, gadB, sucA, and sucB in the 50°C group was downregulated, but upregulated in EW exposed cells. The expression of most genes was reduced in response to the combined treatment, with 0.024-and 0.286-fold downregulation of udk (encoding uridine kinase) and gadA (encoding glutamate dec-arboxylase alpha), respectively, being observed in cells treated with EW at 50°C. These results provided further evidence of the metabolomic and transcriptomic response of E. coli O157:H7 to oxidation and heat stress.

Electrolysed water (EW) generated using sodium chloride (NaCl) and sodium bicarbonate (NaHCO3) as electrolytes shows strong bactericidal effects on pathogens. However, the sanitising effect of EW generated by adding NaHCO3 before and after electrolysis was not clear. The difference of the bactericidal mechanism in broth medium and real food system was not elucidated as well. This present study aimed to compare the antibacterial effect and inactivation mechanism of EW generated by the addition of NaHCO3 before and after electrolysis against Listeria innocua ATCC 33090 in broth and on shrimp. The addition of NaHCO3 before electrolysis enhanced both in vitro and in vivo antibacterial activity with greater bacterial reduction (2.9 log CFU/mL and 1.7 log CFU/g, respectively) compared with adding NaHCO3 after electrolysis. The antibacterial mechanism was further investigated by NMR-based metabolomics. The EW generated by adding NaHCO3 before electrolysis mainly affected amino acid metabolism and carbohydrate and energy metabolism in broth. The reduction of fewer types of amino acids and sugars was observed on the shrimp attributing to the different nutritional compositions of shrimp. Moreover, the accumulation of γ-aminobutyric acid and glutamate in L. innocua on shrimp compensated for the disrupted TCA cycle caused by the EW stress. Therefore, L. innocua was less sensitive to generated EW on shrimp as compared with in broth. The results provide comparative information on the responses of L. innouca to EW stress in broth and on shrimp and could serve as the basis to develop strategies to better control pathogens in food.

To maintain the quality and shelf life of cherry tomatoes, microbial decontamination is essential. The objective of this study was to determine the effect of acidic electrolyzed water (AcEW), hydrogen peroxide (H2O2), ozone water (O3) and sodium hypochlorite (NaClO) on quality, shelf life and microbial decontamination of cherry tomatoes. Water was used as control. AcEW, H2O2, O3 and NaClO were sprayed one day prior to harvest. Afterwards, tomato fruits were stored at 5 ˚C to determine their quality, shelf life and microbial activity. Respiration (p ≤ 0.001) and ethylene production (p ≤ 0.01) were significantly lower in O3-treated tomato fruits compared to those in other treatments. The lowest fresh weight loss and the longest shelf life 20 days (p ≤ 0.05) were found for O3-treated tomato fruits. Their fungal incidence rate (p ≤ 0.001) and microbial activity were the lowest. However, fruits firmness 13.36N (p ≤ 0.01) was significantly retained for O3-treated tomato fruits. Color development, lycopene content and fructose and glucose contents suppressed by O3-treatment might have prolonged the shelf life of tomato fruits. Based on comprehensive results of physiological, physicochemical and microbiological analysis, O3-treated tomato fruits prolonged shelf life and maintained their quality at 5˚C. Therefore, O3-treatment might have great potential to be used for long time storage of cherry tomatoes.

Washing water used for processing fruits and vegetables can convey spoilage fungi and bacteria. The common procedure to reduce microbial contamination involves the use of chlorine based compounds. Recently, electrolyzed water (EW) has been evaluated as an alternative measure in controlling microbial spoilage contamination occurring during washing steps. This work reviews results related to the application of EW for controlling microbial viability responsible for decay development during storage period. EW produced with sodium bicarbonate as electrolyte reduced Penicillium spp. population in water and, consequently, green mould decay in citrus fruits; the use of sodium chloride in EW production inactivated spores of Fusarium sp. in water and reduced pineapple decay during storage at 12°C for 20 days as well as controlled yeast and mould population in date fruit up to six months of cold storage. EW was also found effective in controlling spoilage bacteria on ready-to-eat produce. Pseudomonas fluorescens, Pantoea agglomerans, and Rhanella aquatilis were undetectable in electrolyzed process water amended with sodium chloride although similar treatment slightly reduced Erwinia carotovora load inoculated onto lettuce. EW at low free chlorine concentration reduced viability of Pseudomonas spp. and psychrotrophic bacteria in both simulated and industrial washing water. EW treatment of fresh cut lettuce dipped in microbial contaminated water reduced Pseudomonas spp. of about 1 log cfu g-1 delaying spoilage symptoms that occurred early in untreated vegetables. These results demonstrate that the use of EW can control spoilage microorganisms in washing water, reduce cross-contamination phenomena and delay fruit and vegetable decay.

Effect of electrolysed water generated by sodium chloride combined with sodium 1 bicarbonate solution against Listeria innocua in broth and on shrimp 2 3 17 18 Highlights 20 21  Adding NaHCO3 before electrolysis enhanced sanitising effect than adding 22 afterwards 23  L. innocua in broth and on shrimp showed different metabolic responses to 24 treatment 25  Amino acid pathways and energy metabolism were altered in L. innocua in broth 26  GABA shunt compensated for the disrupted TCA cycle caused by EW stress on 27 shrimp 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 Abstract: 43

Background: Electrolyzed oxidizing water (EOW) is a novel natural disinfectant. It has been suggested that applying EOW can improve the shelf life of fish. The purpose of this research was to compare the effect of electrolyzed water with a solution of alginate coating prepared/followed by EOW and examine their impact on pseudomonas aeruginosa growth inhibition in salmon fillets kept under refrigeration.
Methods: Fish fillets were inoculated with pseudomonas aeruginosa and divided into six different treatment groups: control (no coating), distilled water, alginate, EOW, EOW & alginate (samples coated with alginate solution prepared by EOW), and EOW+ alginate (samples immersed in EOW, then coated with alginate solution). The fillets were kept at 4 °C, and the bacterial count was determined on days: 0, 2, 4, 8, and 12. Data analysis was performed using repeated ANOVA and Bonferroni post-hoc test at statistical significance of 0.05.
Results: Additionally, both the solo and combined application of electrolyzed water and alginate coating have been shown to substantially limit developing Pseudomonas aeruginosa. However, their combined usage had a greater impact than control sample. When coating solution was applied followed by electrolyzed water, the greatest decrease rate (1.27 logs CFU/g) was found in comparison to control samples.
Conclusion: According to the findings, applying alginate coating in conjunction with electrolyzed water may be used realistically in food systems, particularly seafood.

In the present study, we evaluated the antimicrobial activity of neutral electrolyzed water (NEW) against 14 strains of spoilage Pseudomonas of fresh cut vegetables under cold storage. The NEW, produced from solutions of potassium and sodium chloride, and sodium bicarbonate developed up to 4000 mg/L of free chlorine, depending on the salt and relative concentration used. The antimicrobial effect of the NEW was evaluated against different bacterial strains at 10 5 cells/ml, with different combinations of free chlorine concentration/contact time; all concentrations above 100 mg/L, regardless of the salt used, were found to be bactericidal already after 2 min. When catalogna chicory and lettuce leaves were dipped for 5 min in diluted NEW, microbial loads of mesophilic bacteria and Enterobacteriaceae were reduced on average of 1.7 log cfu/g. In addition, when lettuce leaves were dipped in a cellular suspension of the spoiler Pseu-domonas chicorii I3C strain, diluted NEW was able to reduce Pseudomonas population of about 1.0 log cfu/ g. Thanks to its high antimicrobial activity against spoilage microorganisms, and low cost of operation, the application of cycles of electrolysis to the washing water looks as an effective tool in controlling fresh cut vegetable microbial spoilage contamination occurring during washing steps.