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.
Document Type: Research Article
Affiliations: 1: Center for Meat Safety & Quality, Department of Animal Sciences, Colorado State University, Fort Collins, Colorado 80523, USA 2: Center for Meat Safety & Quality, Department of Animal Sciences, Colorado State University, Fort Collins, Colorado 80523, USA. firstname.lastname@example.org
Publication date: April 1, 2011
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