title: Effect of the food matrix on pressure resistance of Shiga-toxin producing Escherichia coli.
abstract: The pressure resistance of Shiga-toxin producing Escherichia coli (STEC) depends on food matrix. This study compared the resistance of two five-strain E. coli cocktails, as well as the pressure resistant strain E. coli AW1.7, to hydrostatic pressure application in bruschetta, tzatziki, yoghurt and ground beef at 600 MPa, 20 °C for 3 min and during post-pressure survival at 4 °C. Pressure reduced STEC in plant and dairy products by more than 5 logs (cfu/ml) but not in ground beef. The pH affected the resistance of STEC to pressure as well as the post-pressure survival. E. coli with food constituents including calcium, magnesium, glutamate, caffeic acid and acetic acid were treated at 600 MPa, 20 °C. All compounds exhibited a protective effect on E. coli. The antimicrobial compounds ethanol and phenylethanol enhanced the inactivation by pressure. Calcium and magnesium also performed protective effects on E. coli during storage. Glutamate, glutamine or glutathione did not significantly influence the post-pressure survival over 12 days. Preliminary investigation on cell membrane was further performed through the use of fluorescence probe 1-N-phenylnaphthylamine. Pressure effectively permeabilised cell membrane, whereas calcium showed no effects on membrane permeabilisation.
authors.affiliation: University of Alberta, Department of Agricultural, Food and Nutritional Science, Edmonton, Canada.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.affiliation: University of Alberta, Department of Agricultural, Food and Nutritional Science, Edmonton, Canada.
authors.forename: Rigoberto
authors.initials: R
authors.lastname: Garcia-Hernandez
authors.affiliation: Alberta Agriculture and Forestry, Food Processing Development Centre, Leduc, Canada.
authors.forename: Darcy
authors.initials: D
authors.lastname: Driedger
authors.affiliation: University of Alberta, Department of Agricultural, Food and Nutritional Science, Edmonton, Canada.
authors.forename: Lynn M
authors.initials: LM
authors.lastname: McMullen
authors.affiliation: University of Alberta, Department of Agricultural, Food and Nutritional Science, Edmonton, Canada; Hubei University of Technology, School of Food and Pharmaceutical Engineering, Wuhan, China. Electronic address: mgaenzle@ualberta.ca.
authors.forename: Michael
authors.initials: M
authors.lastname: Gänzle
mesh_terms: D000818:Animals; D002417:Cattle; D015169:Colony Count, Microbial; D005519:Food Preservation / Q000295:instrumentation / Q000379:methods*; D005520:Food Preservatives / Q000494:pharmacology; D006874:Hydrostatic Pressure; D008460:Meat / Q000382:microbiology*; D054323:Shiga-Toxigenic Escherichia coli / Q000737:chemistry / Q000187:drug effects / Q000254:growth & development*; D015014:Yogurt / Q000382:microbiology*
chemical_list: D005520:Food Preservatives
keywords: Escherichia coli; Food matrix; High pressure; Membrane; Shiga-toxin producing E. coli (STEC)