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using a scanning electron microscope. The cells treated with electrolyzed acidic water had wrinkled cell wall with round pores in which the cytoplasmic structures were flushed out (Osafune, Ehara, & Ito, 2006). Little reports on the effects of chlorine, pH and ORP values of the EO water in inactivation of pathogens are available. Kim et al. (2000b) have developed chemically modified water from deionized water with the same proper- ties (i.e., pH, chlorine and ORP) as EO water without using electrolysis. Their results suggested that ORP of EO water might be the primary factor responsible for the bactericidal effect. However, Koseki et al. (2001) noted that the ORP is not the main factor of antimicrobial activity because the higher ORP of ozonated water did not show higher disin- fectant effect than lower ORP of EO water. They further defined that free chlorine of EO water, mainly hypochlo- rous acid (HOCl), produces hydroxyl radical (OH) that acts on microorganisms. Ozone solution produces OH, too. The higher OH produced by higher HOCl concentra- tion in EO water means the better the disinfectant efficacy than ozone solution. Len et al. (2000) reported that the rel- ative concentrations of aqueous molecular chlorine, HOCl, hypochlorite ion (OCl) and chlorine gas (Cl2) were also the factors that accounted for the bactericidal potency. At pH 4, EO water with the maximum concentration of HOCl had the maximum microbicidal activity. Park et al. (2004) investigated the effects of chlorine and pH on efficacy of EO water for inactivating E. coli O157:H7 and L. monocytogenes. It was demonstrated that EO water is very effective for inactivating E. coli O157:H7 and L. mon- ocytogenes in a wide pH range (between 2.6 and 7.0), if suf- ficient free chlorine (>2 mg/L) is present. For each chlorine content, bactericidal activity and ORP increased with decreasing pH. Based on fluorescent and spectroscopic measurements, Liao et al. (2007) reported that the ORP of EO water could damage the outer and inner membranes of E. coli O157:H7. The redox state of the glutathione disul- fide–glutathione couple (GSSG/2GSH) can serve as an important indicator of redox environment. There are many redox couples in a cell that work together to maintain the redox environment. The inactivation mechanism hypothe- sized was that ORP could damage the redox state of GSSG/2GSH and then penetrate the outer and inner mem- branes of cell, giving rise to the release of intracellular com- ponents and finally cause the necrosis of E. coli O157:H7. Thus, the antimicrobial effect of EO water derives from the combined action of the hydrogen ion concentration, oxidation–reduction potential and free chlorine. Storage conditions can affect chemical and physical properties of EO water. When stored under an open, agi- tated and diffused light condition the EO water had the highest chlorine loss rate. Under open condition, chlorine loss through evaporation followed first-order kinetics. The rate of chlorine loss was increased abound 5-fold with agitation, but it was not significantly affected by diffused light (Len, Hung, & Chung, 2002). EO water exposed to the atmosphere could reduce more chlorine and oxygen than that kept to a closed systems for a longer time (Hsu & Kao, 2004). Fabrizio and Cutter (2003) reported that EO water stored at 4 °C was more stable than stored at 25 °C. The effectiveness of chlorine as a bactericidal agent is reduced in the presence of organic matter due to the forma- tion of combined available chlorines. At an identical chlo- rine concentration, the combined available chlorines had much lower bactericidal activity than the free form (Oomori, Oka, Inuta, & Arata, 2000). For practical appli- cation, EO water usually must be used in the presence of amino acids or proteins containing materials produce a combined form. Although the electrolyzed solution is not a newly discovered disinfectant, it is important to examine its bactericidal effect on different bacteria (Table 1). 6. Inactivation of blood-virus using EO water Researchers also indicated that EO water has antiviral potency on blood borne pathogenic viruses including hep- atitis B virus (HBV), hepatitis C virus (HCV) (Morita et al., 2000; Sakurai et al., 2003; Tagawa et al., 2000) and human immunodeficiency virus (HIV) (Kakimoto et al., 1997; Kitano et al., 2003; Morita et al., 2000). EO water contained only 4.2 mg/L of free chlorine (pH 2.34, ORP 1053 mV) had a greater efficacy against hepatitis B virus surface antigen (HBsAg) and HIV-1 than sodium hypo- chlorite (Morita et al., 2000). The possible mechanisms underlying the EO water disinfection against blood-borne viruses might include (1) inactivation of surface protein; (2) destruction of virus envelope; (3) inactivation of viral nucleic acids encoding for enzymes; and (4) destruction of viral RNA (Morita et al., 2000). Hanson, Gor, Jeffries, and Collins, 1989 demonstrated that dried HIV is relatively resistant against disinfectants compared with wet HIV. In an insightful work, Kitano et al. (2003) stated that EO water has an inactivation potential against the infectivity of dried HIV-1. They found that the viral reverse transcript (RT) and the viral RNA in HIV-1 are targets of EO water. Sakurai et al. (2003) reported experiments with HBC and HCV-contaminated endoscopes, and concluded that nei- ther HBV nor HCV was detected after the endoscopes were cleaned manually with a brush and disinfected with EO water. Viral DNA was not detected from any endoscope experimentally contaminated with viral-positive mixed sera (Lee et al., 2004; Tagawa et al., 2000). Thus, EO water directly inactivates viruses and its clinical application is rec- ommended. Effectiveness of EO water in preventing viral infection in the food field needs to be further studied. 7. Inactivation of toxins using EO water Staphylococcal food poisoning results from the con- sumption of a food in which enterotoxigenic staphylococci have grown and produced toxins. Within 1–6 h after inges- tion of staphylococcal enterotoxin (SEs)-contaminated foods, victims experience nausea, abdominal cramps, vom-PDF Image | electrolyzed water in the food industry ROC
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