EO water used as a disinfectant in the food industry

1. Use of EO water for food processing equipment

EO water has been used as a disinfectant for food pro- cessing equipment (Table 2). Venkitanarayanan et al. (1999a) reported EO water could be used as an effective method for eliminating food-borne pathogens on cutting boards. EO water (pH of 2.53, ORP of 1178 mV and chlo- rine of 53 mg/L) could also reduce Enterobacter aerogenes and S. aureus on glass, stainless, steel, glazed ceramic tile, unglazed ceramic tile and vitreous china surfaces. Immer- sion of these surfaces in EO water for 5 min with agitation (50 rpm) reduced populations of E. aerogenes and S. aureus on the tested surfaces to <1 CFU/cm2 (Park et al., 2002b). Listeria monocytogenes is a food-borne pathogen that can lead to potentially life-threatening listeriosis in high-risk populations. Listeriosis outbreaks have been associated with processed foods and the formation of L. monocytoge- nes biofilms in the processing environment is an important source for secondary contamination (Carpentier & Chassa- ing, 2004).

Frank and Koffi (1990) and Lee and Frank (1991) ear- lier reported that L. monocytogenes biofilms are resistant to chlorine, acid anionic and quaternary ammonium sani- tizers, so that inadequate cleaning and sanitation of food processing surfaces may lead to spread of the pathogen throughout the entire processing plant. Kim et al. (2001) investigated the resistance of L. monocytogenes biofilms on stainless steel surfaces to EO water (pH of 2.60, ORP of 1160 mV and chlorine of 56 mg/L) and found that a 300-s treatment on a stainless steel surface, could reduce the L. monocytogenes from 1.9 · 1010 CFU/82.5 cm2 to below detection levels (5 CFU/coupon). However, it took 300 s of exposure to 200 mg/L chlorine solution to achieve the same result. Ayebah et al. (2005) recently inactivated L. monocytogenes biofilms on stainless steel surfaces with a combination of ER and EO water. They found that ER water alone did not significantly reduce the L. monocytog- enes biofilms. Treatment with EO water for only 30–120 s reduced the viable bacteria populations in biofilms by 4.3–5.2 log CFU per coupon (2 by 5 cm), whereas the com- bined treatment of ER water followed by EO water could produce an additional reduction by 0.3–1.2 log CFU per coupon.

Stainless steel has been the most commonly used mate- rial for food contact surfaces in the food industry. Ayebah and Hung (2005) reported that EO water (pH of 2.42, ORP of 1077 mV and free chlorine of 50 mg/L) and modified EO water (pH of 6.12, ORP of 774 mV and free chlorine of 50 mg/L) did not have any adverse effect on stainless steel for a period of 8 days.

The effect of EO water in reducing bacteria in the pipe- lines of the milking system has been investigated (Walker et al., 2005a, 2005b). A 10 min wash with 60 °C ER water followed by a 10 min wash with 60 °C EO water success- fully removed all detectable bacteria from the non-porous milk contact surfaces and ATP residue tests were nega- tive. These results indicated that EO water has the poten- tial to be used as a cleaning and sanitizing agent for cleaning in place (CIP) cleaning of on-farm milking systems.

2. Use of EO water for vegetables

Electrolyzed water has been used to inactivate pathogens on fresh produce (Table 3). Izumi (1999) has demonstrated that EO water is usable for cleaning fresh-cut carrots, bell peppers, spinach, Japanese radish and potatoes. The pre- cut produces, treated with EO water (pH 6.8, 20 mg/L free chlorine) by dipping, rinsing or dipping/blowing, showed a bacterial reduction by 0.6–2.6 logs CFU/g. The EO water containing 50 mg/L chlorine had a stronger bactericidal effect than that containing 15 or 30 mg/L chlorine. The treatment did not cause discoloration of fresh-cut produces. Rinsing EO water (50 mg/L) treated fresh-cut produces with fresh water did not increase the bacterial reduction due to the additive effects of the sequential treatment. Koseki et al. (2004b) reported that cucumbers washed with

ER water (pH of 11.3, ORP of