Food industry

Electrolysed water (EW) is gaining popularity as a sanitiser in the food industries of many countries. Electrolysis dissociates a dilute sodium chloride solution into acidic electrolysed water (AEW, anolyte) — pH 2–3, an oxidation-reduction potential of about 1,100 mV and 10–90 ppm active chlorine — and basic electrolysed water (BEW, catholyte), with a pH of 10–13. Vegetative cells of various bacteria in suspension were generally reduced by 6.0 log CFU/ml with AEW.

Typical food industry sanitisers include chlorine compounds, organic acids, trisodium phosphate, iodophores and quaternary ammonium compounds. Chlorine compounds are often the most effective, but can be more corrosive and irritating. Some decontamination procedures have been found unacceptable because of chemical residues, high cost, limited effectiveness or product discolouration. EW is increasingly used to reduce or eliminate bacteria on food products, food-processing surfaces and non-food-contact surfaces. Japan's Ministry of Health, Labour and Welfare has approved EW as a food additive, and the U.S. Environmental Protection Agency has approved EW generators for use in the food industry.

How electrolysed water works

EW was originally developed in Russia, where it has been used for water decontamination, regeneration and disinfection in medical institutions, and has been used in Japan since the 1980s. It is produced by electrolysing a dilute NaCl solution in a cell where a diaphragm separates anode and cathode. The anodic solution has a pH of 2–3, an ORP above 1,100 mV and 10–90 ppm active chlorine; the cathodic solution has a pH of 10–13 and an ORP of −800 to −900 mV. Neutral electrolysed water (pH 7–8, ORP about 750 mV) is produced by mixing the anodic solution with OH⁻ ions.

AEW has strong antimicrobial activity. Chlorine and a high ORP appear to be the main contributors; the low pH sensitises bacterial cells to hypochlorous acid, the most active of the chlorine compounds, which penetrates cell membranes and oxidises key metabolic systems. BEW is mostly used as a cleaner and degreaser before disinfection — and pretreatment with BEW followed by AEW was more effective in some applications than AEW alone.

Results on surfaces, utensils and process water

• Cutting boards: Vibrio parahaemolyticus fell from 5.8 to below 1.0 log CFU/cm² after one minute of AEW; rinsing plastic boards with neutral EW reduced E. coli, S. aureus, P. aeruginosa and L. monocytogenes by about five orders of magnitude.
• Processing gloves: L. monocytogenes was completely inactivated on every glove type after five minutes.
• Stainless steel and tiles: V. parahaemolyticus was reduced by more than 5.0 log CFU/cm² within a minute.
• Biofilms: AEW reduced L. monocytogenes in biofilms on stainless steel to non-detectable levels within five minutes.
• Abattoirs: after standard pre-cleaning, AEW was more effective than a common sanitiser across slaughterhouse areas; spraying cattle hides with BEW then AEW cut total counts by 3.5 log.
• Process water: electrolysing vegetable wash water with a little added salt reduced the tested bacteria by about four orders of magnitude, with complete inactivation at higher current.

Results on food products

• Fruit and vegetables: ten minutes of AEW reduced aerobic bacteria, coliforms and fungi on strawberries to non-detectable levels; on tomatoes, E. coli O157:H7, L. monocytogenes and Salmonella Enteritidis fell by about 7.5 log. On leafy greens, AEW was as effective as chlorine.
• Fish and seafood: 15 minutes of AEW cut total counts on carp skin by 2.8 log CFU/cm².
• Poultry and meat: spraying chicken carcasses with BEW and then immersing them in AEW gave reductions of 1.5–2.4 log, and AEW extended the shelf life of refrigerated poultry. Decontaminating carcasses with AEW was found the most cost-efficient way to reduce Campylobacter along the poultry chain.
• Eggs: electrostatic spraying of shell eggs reduced E. coli, S. aureus and Salmonella Typhimurium by 3–6 orders of magnitude.
• As ice: frozen AEW both refrigerates and controls pathogens — it extended the shelf life of Pacific saury and stopped coliform growth.

D. Hricova, R. Stephan and C. Zweifel — Electrolyzed Water and Its Application in the Food Industry