Stability of Slightly Acidic Electrolyzed Water on Storage and its Microbial Inactivation Effectiveness on the Aerobic Microflora Present on Intact Spinach (Spinacia oleracea L.) Leaves

Abstract

The stability of Slightly Acidic Electrolyzed Water (SAEW) on storage was evaluated. SAEW samples of known initial Oxidation Reduction Potential (ORP, mV), pH and available chlorine concentration (ACC, mg/L) were stored at 25°C in different containers and changes of ORP, pH and ACC were monitored daily for a period of 10 days. ORP, pH and ACC were respectively maintained at 900-1000mV, 5-6.5 and 10-30mg/L. SAEW was further evaluated for its microbial inactivation effectiveness on the aerobic microflora present on spinach (Spinacia oleracea L.) expressed as aerobic plate count (APC) and was compared to Sodium hypochlorite (NaOCl) solution. The decontamination was done by dipping spinach samples with or without a pre-washing step into treatment solution for 5min. SAEW (pH 5.5, 25mg/L ACC) achieved a significantly higher microbial reduction than NaOCl solution (pH 9.9, 103mg/L ACC). While pre-washing of spinach in running tap water for 5min increased the microbial reduction by SAEW from 1.3 logo colony forming units (CFU)/g to more than 2 log10 CFU/g at 5min contact time, increasing exposure time did not significantly affect its antimicrobial effectiveness on spinach aerobic microflora.