Elimination of Escherichia coli from oysters using electrolyzed seawater

Electrolyzed seawater (ESW) is reportedly an effective disinfectant for aquaculture equipment because of its simple mechanism and cost effectiveness. The potential of electrolyzed seawater for oyster depuration was studied using different experiments. The first was determination of chlorine tolerance of oysters. Second was effectiveness of ESW against Escherichia coli in artificially contaminated oysters and third was effectiveness of ESW against E. coli in naturally contaminated oysters from two culture farms. Tolerance of oysters for Chlorine was studied by scanning electron microscopy (SEM) and histological observation demonstrating that more than 0.5 mg/L of chlorine was toxic while 0.2 mg/L was safe for the oysters. Oysters artificially contaminated with E. coli (230 MPN/100 mL, 16.5 °C for 15 h) were depurated for 6, 24, and 48 h using ESW and UV irradiated seawater. E. coli counts in artificially contaminated oysters decreased to below the detection limit (30 E. coli MPN/100 g) after depuration with ESW for 24 h or UV irradiated seawater for 6 h. In experiments on naturally contaminated oysters E. coli counts decreased to below detection limits after depuration with ESW for 24 h. From these results, electrolysis of seawater is a useful method for post harvest elimination of E. coli from oysters.