IAFP 2009 Program Book and Abstract Book - AB48

T6-09 Thermal Inactivation of Escherichia coli O157:H7 in Nonintact Beef Steaks of Different Thickness by Different DSC Cooking Methods and Equipment CANGLIANG SHEN, Jeremy M. Adler, Ifigenia Geornaras, Keith E. Belk, Gary C. Smith and John N. Sofos Colorado State University, Dept. of Animal Sciences, Fort Collins, CO, USA Introduction: Outbreaks of Escherichia coli O157:H7 from nonintact beef products have been attributed to inadequate cooking or cooking from the frozen state. Evidence has indicated that when cooking to a given internal temperature, pathogen lethality increases with steak thickness. Purpose: This study compared thermal inactivation of E. coli O157:H7 in non-intact beef steaks of different thickness, cooked to an internal temperature of 65°C by three cooking methods and with different cooking equipment. Methods: Fresh beef (5% fat) was coarse-ground, and batches (1 kg) were mixed with a composite (50 ml) of rifampicinresistant E. coli O157:H7 (8-strain, 6.4 ± 0.1 log CFU/g) and sodium chloride (0.5%) plus sodium tripolyphosphate (0.25%) solution (50 ml), extruded into casings (10 cm diameter), and placed at -20°C for 6 h. Semi-frozen beef was cut into 1.5, 2.5 and 4.0 cm thick steaks, vacuum-packaged, frozen (-20°C, 48-h ), and tempered (4°C, 2.5 h) before cooking. Steaks were double pan-broiled (George Foreman® grill), pan-broiled (Presto® electric skillet and Sanyo® grill) or roasted (Oster® toaster and Magic Chef® kitchen oven) to 65°C. Temperatures of cooking equipment surfaces and meat samples were monitored with thermocouples. Samples were analyzed for survivors on tryptic soy agar plus sodium pyruvate (0.1%, TSAP) and TSAP plus rifampicin (100 µg/ml). Data (two replicates/three samples each) were analyzed using the mixed model of SAS including independent variables and interactions. Results: The order of pathogen inactivation was roasting (2.0 to 4.2 log CFU/g) > pan-broiling (1.6 to 2.8 log CFU/g) ≥ double pan-broiling (1.2 to 2.3 log CFU/g). Cooking of 4.0 cm thick steaks required a longer time (20 to 65 min; variation due to different cooking equipment) and caused greater (P < 0.05) reductions in counts (2.3 to 4.2 log CFU/g) than in thinner samples. The time to reach the target temperature increased in order of George Foreman® grill (3.9 to 19.8 min) < Oster® toaster (11.3 to 45.0 min) < Presto® electric skillet (16.3 to 55.0 min) < Sanyo® grill (14.3 to 65 min) < Magic Chef ® kitchen oven (20.0-63.0 min), with time differences within each equipment related to steak thickness. Significance: Increased steak thickness allowed greater inactivation of E. coli O157:H7, as time to reach the target internal temperature increased. Roasting in a kitchen oven was most effective for pathogen inactivation. T6-10 Ability of Chemically Softened Water to Rinse Bacteria from the Skin of Processed Broiler ARTHUR HINTON and Ronald A. Holser USDA-ARS-RRC, Athens, GA, USA Introduction: The quality of water used in cleansing operations in commercial poultry processing facilities may have an effect on the efficacy of sanitation operations in these facilities. Water hardness is a characteristic of water that is related to the concentration of calcium and magnesium dissolved in the water. The high concentration of dissolved minerals makes hard water a less effective cleanser than soft water, which contains a lower concentration of minerals; therefore, hard water may also be less effective at removing bacterial contamination from broiler skin. Purpose: The purpose of this experiment was to examine the ability of hard water that was chemically softened by the addition of various concentrations of potassium citrate to rinse bacteria from the skin of processed broiler chickens. Methods: Artificial hard water (200 ppm total hardness) was prepared by dissolving 0.38 g calcium chloride and 0.175 g magnesium chloride hexahydrate per liter of distilled water. Hard water was then chemically softened by dissolving 0.0, 1.0, 2.5, or 5.0% (w/v) potassium citrate in the water. Skin samples taken from breasts of broiler carcasses were rinsed five consecutive times in fresh aliquots of chemically softened water, and bacteria in the final skin rinsate were enumerated. Results: Results indicated that significantly (P < 0.05) fewer bacteria were recovered on Eosin Methylene Blue and Campylobacter Agars from skin rinsed in hard water softened with 5.0% citrate than from skin rinsed in water softened with 0.0, 1.0, or 2.5% citrate. Water hardness had no effect on the number of bacteria recovered on Staphylococcus or Plate Count Agars, however. In vitro tests indicated that potassium citrate was not bactericidal towards Escherichia coli, Campylobacter jejuni, or Staphylococcus simulans isolates recovered from broiler skin. Significance: Findings from these experiments indicate that water hardness can play a role in the ability of water to rinse intestinal bacteria from the skin of processed broiler chickens. Since potassium citrate possessed no bactericidal activity, differences in the number of bacteria recovered from the skin was probably due to the differences in the ability of the rinse waters to physically remove bacteria from the skin. Therefore, poultry processors may be able to reduce the number of bacteria on processed poultry by monitoring and controlling the hardness of water used to wash carcasses in processing operations. T6-11 Same Day Detection of Escherichia coli O157:H7 in Large Samplings (3.75 kg) of Fresh or Frozen Raw Ground Beef Using Post Growth Sample Pooling, Re-circulating IMS and Real-time PCR John Murray, Nicole Prentice, Brooke V. Houston, Paul M. Benton, Katarzyna Brzegowa, Marcie Van Wart, Christine M. Aleski, Michael F. Scott and ADRIAN PARTON MATRIX MicroScience Ltd., Cambridgeshire, United Kingdom Introduction: E. coli O157:H7 has become notorious as a foodborne pathogen because of its low infective dose, its ability to survive for prolonged periods in frozen beef samples and the severity of the disease in vulnerable individuals. Raw ground beef has been implicated as the source of E. coli O157:H7 in a significant number of foodborne disease outbreaks and food safety recalls during the past two decades. Detecting the presence of this STEC at low levels in raw beef presents significant challenges to both the food industry and regulatory agencies. Purpose: This study describes the development and validation of a robust re-circulating IMS (RIMS) method that allows post-growth sample pooling, rapid isolation and detection of E. coli O157:H7 from large (10 × 375 g) raw ground 48 — Abstract Book Technical

IAFP 2009 Program Book and Abstract Book

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