Effect of Slightly Acidic Electrolyzed Water for Inactivation of Escherichia coli on White Shrimp (Litopenaeus vannamei )

The influence of slightly acidic electrolyzed water (SAEW) for inactivation of Escherichia coli on white shrimp (Litopenaeus vannamei) under different washing conditions was investigated. At room temperature, effectiveness of SAEW (with available chlorine concentration of 20 mg/L, pH of 6.1 and ORP of 812 mv ) to inactive Escherichia coli with different dipping times (2 min, 5 min, and 10 min), weight ratio of shrimp to SAEW (1:4, 1:10, and 1:20), with or without vibration were compared. Bacterial cells were counted using a dilution plate count and each sample was inoculated with E coli. with initial concentration of 106 CFU/ml. The results showed that the effective order of time on bactericidal activity of SAEW was 10 min > 5 min > 2 min under the same ratio of shrimp to SAEW. Increasing the amount of SAEW enhanced the bactericidal effect obviously. Significant differences were observed in the bactericidal activity with or without vibration. For the ratio of 1:4, the number of E coli. on shrimp was reduced by 1.60 lgCFU/ml after treatment for 5 min without vibration, while 3.30 lgCFU/ml bacterial reduced with vibration at 2000 rpm. This study suggests that the SAEW treatment with suitable washing method could be a practicable way to effectively control Escherichia coli contamination on white shrimp.