title: Thermal inactivation of acid, cold, heat, starvation, and desiccation stress-adapted Escherichia coli O157:H7 in moisture-enhanced nonintact beef.
abstract: This study was conducted to compare thermal inactivation of stress-adapted and nonadapted Escherichia coli O157:H7 in nonintact beef moisture enhanced with different brine formulations and cooked to 65°C. Coarsely ground beef was mixed with acid, cold, heat, starvation, or desiccation stress-adapted or nonadapted rifampin-resistant E. coli O157:H7 (eight-strain mixture, 5 to 6 log CFU/g) and a brine solution for a total moisture enhancement level of 10%. The brine treatments included distilled water (control), sodium chloride (0.5% NaCl) plus sodium tripolyphosphate (0.25% STP), or NaCl + STP combined with cetylpyridinium chloride (0.2% CPC), lactic acid (0.3% LA), or sodium metasilicate (0.2% SM). The treated meat was extruded into bags (15 cm diameter), semifrozen (-20°C for 4.5 h), and cut into 2.54-cm (1-in.)-thick portions. Samples were individually vacuum packaged, frozen (-20°C for 42 h), and tempered at 4°C for 2.5 h before cooking. Partially thawed (-1.8 ± 0.4°C) samples were pan broiled to an internal temperature of 65°C. Pathogen counts of partially thawed (before cooking) samples moisture enhanced with brines containing CPC, LA, or SM were 0.7 to 1.1, 0.0 to 0.4, and 0.2 to 0.4 log CFU/g, respectively, lower than those of the control. Compared with microbial count reductions obtained after pan broiling of beef inoculated with nonadapted E. coli O157:H7 cells, count reductions during cooking of meat inoculated with cold and desiccation stress-adapted, acid stress-adapted, and heat and starvation stress-adapted cells indicated sensitization, cross protection, and no effect, respectively, of these stresses on the pathogen during subsequent exposure to heat. Among all stressed cultures, CPC-treated samples (0.8 to 3.6 log CFU/g) and LA-treated samples (0.8 to 3.5 log CFU/g) had the lowest numbers of E. coli O157:H7 survivors after cooking.
authors.affiliation: Center for Meat Safety & Quality, Department of Animal Sciences, Colorado State University, Fort Collins, Colorado 80523, USA.
authors.forename: Cangliang
authors.initials: C
authors.lastname: Shen
authors.forename: Ifigenia
authors.initials: I
authors.lastname: Geornaras
authors.forename: Keith E
authors.initials: KE
authors.lastname: Belk
authors.forename: Gary C
authors.initials: GC
authors.lastname: Smith
authors.forename: John N
authors.initials: JN
authors.lastname: Sofos
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D002417:Cattle; D003080:Cold Temperature; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D019453:Escherichia coli O157 / Q000254:growth & development / Q000502:physiology*; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008460:Meat / Q000382:microbiology*; D013312:Stress, Physiological; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water