title: Modulation of wound-induced hydrogen peroxide and its influence on the fate of Escherichia coli O157:H7 in cut lettuce tissues.
abstract: Wounding of lettuce tissue has been examined previously by others in regard to browning reactions, and treatments to modulate wounding responses were evaluated for reduction of browning. However, the wounding process also releases oxygen radicals such as hydrogen peroxide. This study  focused on the evaluation of two treatments that reduce hydrogen peroxide at cut surfaces (heat treatment and pyruvate addition) and one treatment that enhances its production (infusion with the fungal elicitor harpin). Hydrogen peroxide changes in response to treatment were also associated  with resultant survival of Escherichia coli O157:H7, which was inoculated onto the lettuce before cutting. Heat-treated lettuce produced significantly less hydrogen peroxide, and microbial analysis showed that E. coli O157:H7 survival on packaged, heat-treated lettuce was higher  than on non-heat-treated controls. Lettuce was also cut under a solution of sodium pyruvate (a well-known hydrogen peroxide quencher), and E. coli O157:H7 survival was found to be enhanced with that treatment. When lettuce was infused with harpin before cutting, hydrogen peroxide  production was enhanced, and this was associated with reduced survival of E. coli O157:H7. These results collectively support the hypothesis that modulation of wound-generated hydrogen peroxide can have an influence on E. coli O157:H7 survival on cut and packaged romaine lettuce.
authors.affiliation: Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre, 4200 Highway 97, Summerland, British Columbia, Canada V0H 1Z0. peter.toivonen@agr.gc.ca
authors.forename: Peter M A
authors.initials: PM
authors.lastname: Toivonen
authors.forename: Changwen
authors.initials: C
authors.lastname: Lu
authors.forename: Susan
authors.initials: S
authors.lastname: Bach
authors.forename: Pascal
authors.initials: P
authors.lastname: Delaquis
mesh_terms: D015169:Colony Count, Microbial; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development; D005511:Food Handling / Q000379:methods*; D006358:Hot Temperature; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D018545:Lactuca / Q000382:microbiology*; D050296:Microbial Viability; D019289:Pyruvic Acid / Q000494:pharmacology
chemical_list: D019289:Pyruvic Acid; D006861:Hydrogen Peroxide