Title: Efficacy of chlorine concentration and acidic electrolyzed water in decontaminating lettuce leaves artificially inoculated with Escherichia coli O157:H7 Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 10, 2008
Publication Date: August 3, 2008
Citation: Keskinen,L.,Burke,A.,Annous,B. 2008.Efficacy of cholorine concentration and acidic electrolyzed water in decomtaminating lettuce leaves artificially inoculated with Escherichia coli O157:H7 [abstract].International Assn for Food Protection.Columbus,OH.p.1. Technical Abstract: Consumption of lettuce has been linked to outbreaks of foodborne illnesses and recalls due to contamination with Escherichia coli O157:H7. Reduction of this risk requires the development of effective and an easily implemented decontamination process. The purpose of this study was to compare the efficacy of industrial chlorine wash (20 ppm) to that of 200 ppm chlorine and electrolyzed water (50 ppm) treatments in reducing populations of E. coli O157:H7 on artificially inoculated lettuce. Fresh-cut leaves of Romaine and Iceberg lettuce were inoculated by immersion in water containing E. coli O157:H7 (8 log CFU/ml) for 5 min and dried in a salad spinner. Leaves were then washed for 2 min, immediately or following 24 h of storage at 4C, using: 1) deionized water; 2) acidic electrolyzed water (50 ppm chlorine and pH 2.6); 3) 20 ppm chlorine; 4) 200 ppm chlorine. Following 2 min treatment, samples were blended in neutralizing buffer (1:3), serially diluted, and surface plated on the selective media CT-SMAC. There was no difference in the levels of E. coli O157:H7 on Romaine or Iceberg leaves at 0 and 24 h. The washing treatment using 200 ppm chlorine resulted in the greatest reduction in E. coli O157:H7 populations (1.84 ± 0.53 and 1.07 ± 0.50 log CFU/g at 0 and 24 h, respectively) as compared to the other wash treatments used (<1 log CFU/g reduction). The industrial chlorine wash was shown to be ineffective in inactivating E. coli O157:H7 cells on lettuce. While the 200 ppm chlorine wash treatment was capable of nearly achieving a 2 log reduction, the process needs to be optimized to meet the FDA 5 log requirement. Currently, research is under way to optimize this wash treatment and compare it to other decontamination treatments including chlorine dioxide gas.