Inactivation of Escherichia coli O157:H7, Salmonella enteritidis and Listeria monocytogenes on the surface of tomatoes by neutral electrolyzed water

M.A. Deza, M. Araujo and M.J. Garrido

Institute of Food Research and Analysis, University of Santiago de Compostela, Santiago de Compostela, Spain

Aims: To determine the efficacy of neutral electrolyzed water (NEW©) in killing Escherichia coli OI57:H7Salmonella enteritidis and Listeria monocytogenes, as well as non-pathogenic E- coli, on the surface of tomatoes, and to evaluate the effect of rinsing with NEW© on the organoleptic characteristics of the tomatoes.

Methods and Results: The bactericidal activity of NEW©, containing 444 or 89 mg1-1 of active chlorine, was evaluated over pure cultures (8.5Iog CFU mI-1) of the above-mentioned strains. All of them were reduced by more than 6 log CFU ml-1 within 5 min of exposure to NEW©. Fresh tomatoes were surface-inoculated with the same strains, and rinsed in NEW© (89 mg1-1 of active chlorine) or in deionized sterile water (control), for 30 or 60 s. In the NEW©treatments, independent of the strain and of the treatment time, an initial surface population of about 5 log CFU was reduced to 5log CFU, and no cells were detected in the washing solution by plating procedure. A sensory evaluation was conducted to ascertain possible alterations in organoleptic qualities, yielding no significant differences with regard to untreated tomatoes.

Significance and Impact of the Study: Rinsing in NEW© reveals as an effective method to control the presence of E. coli O157:H7, S. enteritidis and L. monocytogenes on the surface of fresh tomatoes, without affecting their organoleptic characteristics. This indicates its potential application for the decontamination of fresh produce surfaces.

Keywords: ANK-Anolyte, disinfectant, E. coli O 157 :H7 , L. monocytogenes, neutral electroly’zed water, organoleptic quality, rinsing fresh tomatoes, S. enteritidis.