Electrolysed Water

EW is an activated liquid, obtained by passing a diluted saline solution (NaCl, KCl or MgCl2) through an electrolytic cell, thus causing the production from the anode side of electrolysed oxidising water (OEW), containing high dissolved oxygen, free chlorine and characterised by a low pH (2.3–2.7) and a high oxidation–reduction potential (ORP > 1,000 mV). At the same time from the cathode side electrolysed reducing water is produced (REW), with high pH (10.0–11.5), high dissolved hydrogen and low ORP (-800 to -900 mV) (Huang et al. 2008; Venturini 2013;

Rui et al. 2011). Of the two solutions, one, the acidic and oxidiser solution, contains hypochlorous acid (HOCl), hydrogen chloride (HCl) and free gas (O2 and Cl2); the other, the basic and the reductant solution, contains sodium hydroxide (NaOH), and, from this, H2 gas is liberated. In Fig. 1, the electrolytic cell for the production of electrolysed water is schematically shown. Using a bath electrolysis without separation baffle, a solution with a pH close to neutral (6.2–6.5), with a low concentration of free chlorine (NEW), is obtained (Venturini 2013).

Due to its properties, and particularly for its bactericidal effect, EW may find several applications in the agriculture and food industry. The disinfectant action is due to several factors that act synergistically: pH; ORP; presence of free chlorine (the disinfecting action is mainly due to the presence of hypochlorous acid) (Venturini 2013). Additionally, the high redox potential induces the modification of the metabolic flows and influences the ATP production, probably due to the variation of the flow of electrons in the cell (McPherson 1993). HOCl, the most

Fig. 1 Scheme of the electrolytic cell for electrolysed water (Venturini 2013)

active of the compounds of chlorine, seems to be the main responsible for the death of the microbial cell, inhibiting the oxidation of glucose, due to the oxidation of the sulfhydryl groups of enzymes involved in carbohydrate metabolism (Marriott and Gravani 2006).

Application of EW as Surface Disinfectant

EW has been successfully utilised as surface disinfectant, for example for cutting surfaces made with different materials (glass, steel, glazed ceramic tiles). OEW can be used to reduce bacterial contamination on teflon, stainless steel and ceramic using short treatments (5 min) (Serraino et al. 2010; Park et al. 2002). However, the bactericidal efficacy of EW depends on the amount of organic matter present on the surfaces. In fact, many disinfectants, including hypochlorite, have a reduced effectiveness in presence of a large amount of organic substance (Bach et al. 2006; Liu et al. 2006). This effect can be reduced using the alkaline EW before application of the acidic solution. Alkaline water contains high concentrations of sodium hydroxide, which exerts a detergent action dissolving fats, proteins and polymeric compounds outside the bacterial membranes. In this manner the action of the acid solution will be greater (Ayebah et al. 2005). Møretrø et al. (2012) reported the effectiveness of EW for the disinfection of surfaces contaminated with Salmonella, even in the presence of biofilm. Bartolome´ et al. (2011a) used EW for cleaning and disinfecting a circuit milking and cooling tank in a herd of dairy cattle by comparing its effectiveness with traditional cleaning chemicals. In this study, EW has been used as a replacement to a chlorinated alkaline detergent with phosphates and an acid descaling. The obtained results suggested that the EW not only preserves the integrity of the milking systems but also ensures a greater degree of sanitisation, compared to the traditional chemical products, besides being a clean and environmentally friendly system.

 
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