Effect of mild heat pre-treatment with alkaline electrolyzed water on the efficacy of acidic electrolyzed water against Escherichia coli O157:H7 and Salmonella on Lettuce

• Published in: Food microbiology Vol. 21; no. 5; pp. 559 - 566
• Main Authors: Koseki, Shigenobu, Yoshida, Kyoichiro, Kamitani, Yoshinori, Isobe, Seiichiro, Itoh, Kazuhiko
• Format: Journal Article
• Language: English
• Published: London Elsevier Ltd 01.10.2004; Elsevier
• Subjects: Acidic electrolyzed water; acids; Alkaline electrolyzed water; alkalinity; antibacterial properties; bacterial contamination; Biological and medical sciences; decontamination; electrolytes; Escherichia coli; Escherichia coli O157:H7; food contamination; Food industries; Food microbiology; food pathogens; fresh-cut foods; Fundamental and applied biological sciences. Psychology; heat treatment; inoculum; Lactuca sativa; Lettuce; Mild heat treatment; pathogen survival; Salmonella; sanitizing; viability; water; Salmonella; Acidic electrolyzed water; Lettuce; Alkaline electrolyzed water; Mild heat treatment; Escherichia coli O157:H7; Water; Water treatment; Heat treatment; Escherichia coli; Bacteria; Enterobacteriaceae
• ISSN: 0740-0020; 1095-9998
• DOI: 10.1016/j.fm.2003.11.004

Cut lettuce dip-inoculated with Escherichia coli O157:H7 and Salmonella was treated with alkaline electrolyzed water (AlEW) at 20°C for 5min, and subsequently washed with acidic electrolyzed water (AcEW) at 20°C for 5min. Pre-treatment with AlEW resulted in an approximate 1.8log10cfu/g reduction of microbial populations, which was significantly (p⩽0.05) greater than microbial reductions resulting from other pre-treatment solutions, including distilled water and AcEW. Repeated AcEW treatment did not show a significant bacterial reduction. Mildly heated (50°C) sanitizers were compared with normal (20°C) or chilled (4°C) sanitizers for their bactericidal effect. Mildly heated AcEW and chlorinated water (200ppm free available chlorine) with a treatment period of 1 or 5min produced equal reductions of pathogenic bacteria of 3log10 and 4log10cfu/g, respectively. The procedure of treating with mildly heated AlEW for 5min, and subsequent washing with chilled (4°C) AcEW for period of 1 or 5min resulted in 3–4log10cfu/g reductions of both the pathogenic bacterial counts on lettuce. Extending the mild heat pre-treatment time increased the bactericidal effect more than that observed from the subsequent washing time with chilled AcEW. The appearance of the mildly heated lettuce was not deteriorated after the treatment. In this study, we have illustrated the efficacious application of AlEW as a pre-wash agent, and the effective combined use of AlEW and AcEW.