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12 Athayde, D.R. et al./IFRJ 25(1) : 11 - 16 can be explained by diluted NaOH and H2, as well a little fraction of hypochorite (OCl-), because chlorine forms changes according to pH (Rahman et al., 2010). Other important parameter that influences the effect of EW together pH and ORP is free chlorine concentration (FCC). When the chlorine content increase, bactericidal activity is higher (Park et al., 2004). Slightly acid electrolyzed water (SAEW) is the third type of EW that can be obtained by electrolysis of a brine. SAEW is a product of electrolysis without membrane presence or with membrane and AEW and BEW mixed in different proportions, according to proposed objectives. Guentzel et al. (2008) related the characterization of SAEW with pH approximate of 6,0-6,5 and ORP 800-900 mV. In this range of pH, 95% of chlorine form in water is HOCl, 5% is OCl- and traces of Cl2 (White, 2010). HOCl is important because chlorine in Cl2 form can volatilize (Cui et al., 2009), and the efficacy against microorganism can be lost. So, neutral pH is a good characteristic against chlorine evaporation, maintenance of HOCl concentration and activity of SAEW in microorganisms (Len et al., 2002), because it is the most germicide form of chlorine in solutions, having sanitizing activity 80 times more efficient than OCl- at equivalent concentrations (Eifert and Sanglay, 2002). Moreover, SAEW is non-corrosive, more stable than AEW in storage conditions and less dangerous to worker health (Cao et al., 2009). Some factors can interfere in EW production, like water flow. It can change FCC and ORP in inverse proportion. Salt concentration of brine affect in direct proportion with FCC and electric conductivity. Temperature has little influence in EW parameters (Hsu, 2005). Total chlorine is the group with all forms like chlorohydrins (fatty acids), chloramines and free chlorine (HOCl, OCl-, Cl2) (White, 2010). Free chlorine have bigger activity than chloramines (Gottardi et al., 2013), although exist in solutions with organic matter all these forms, generally the FCC is analysed. In works exist a wide range of FCC applied, which can be since 0,1 to more of 100 mg/L of Cl2 (Fabrizio and Cutter, 2004; Cao et al., 2009; Guentzel et al., 2010; Quan et al., 2010; Ding et al., 2011; Issa- Zacharia et al., 2011; Rahman et al., 2011; Arévalos- Sanchéz et al., 2012; Feliciano et al., 2012; Al-Holy and Rasco, 2015; Martínez-Hernández et al., 2015). It means that low concentration of chlorine can be active in bacteria, but in this cases other parameters must be adjusted, like dipping time (Arévalos-Sanchez et al., 2013; Al-Holy and Rasco, 2015) or amount of water and pressure in spray (Northcutt et al., 2007). The combination of EW with other chemical substances applied together was also study (Arévalos-Sanchez et al., 2012; Chen et al., 2015; Mansur et al., 2015). In places where water is already used, a little number of modifications in the water system are needed. High FCC must be used in a caution way, because chlorine is dangerous to health of workers, causing damage to respiratory tract (when gas evaporate), irritation to skin (direct contact) and others (WHO, 2000). A range of FCC must be determined together with pH for better action in microorganism as well as application form. Advantages and disadvantages In the concept of EW, main advantages are the use of a brine to production, and possibility of local obtainment (Al-Haq et al., 2005; Huang et al., 2008). Other advantages are safety of EW at neutral or basic pH, when HOCl or OCl- are present respectively (White, 2010) that have good action in microorganisms and low capacity of evaporation. Other advantage is a big number of applications, like spray, ice and dipping food in EW. EW can be prepared relatively quickly and easily, with low production cost, avoid chemical products transportation, storage and environmental risk. New technologies have the advantage of new and innovative possibilities of use. The amount of information about new technologies generally is a problem, specially the absence of them. EW have disadvantages like evaporation of Cl2 and loss of activity, mainly at lower pH. Along electrolysis, Cl2 and H2 are produced (Huang et al., 2008), and this can affect worker health, like respiratory tract, besides fact of explosion in higher concentrations. Application time is other disadvantage factor, because the longer the time, better the activity in microrganism. A disadvantage is the initial cost of equipment, which is generally high. Because the interactions of chlorine with proteins and fats, organic matter can cause decrease in EW activity (Cressey et al., 2008). Action mechanisms of EW Actually, isn’t a consensus about EW mechanism, but exist a lot of theories. ORP of AEW can cause damage to E. coli O157:H7 on bacterial ORP and attack inner and outer membranes, causing necrosis of cells (Liao et al., 2007), with damage verified with microscopy (Feliciano et al., 2012). SAEW have equal or higher activity in bacteria than AEW or sodium hypochlorite (NaOCl) at same concentrations and FCC (Cao et al., 2009) with advantage of few free chlorine (Rahman et al., 2012). HOCl can change bacterial respiration destroying the electron transportPDF Image | electrolyzed water in food industries
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