Evaluation of Consumer-Style Cooking Methods for Reduction of Escherichia coli O157:H7 in Ground Beef

2003 ◽  
Vol 66 (6) ◽  
pp. 1030-1034 ◽  
Author(s):  
MIN-SUK RHEE ◽  
SUN-YOUNG LEE ◽  
VIRGINIA N. HILLERS ◽  
SANDRA M. McCURDY ◽  
DONG-HYUN KANG
Keyword(s):  
Escherichia Coli ◽  
Thermal Inactivation ◽  
Ground Beef ◽  
Cooking Methods ◽  
Escherichia Coli O157 ◽  
Phenol Red ◽  
Internal Temperature ◽  
E Coli ◽  
The One ◽  
Time Required

The objective of this study was to evaluate the thermal inactivation of Escherichia coli O157:H7 in ground beef cooked to an internal temperature of 71.1°C (160°F) under conditions simulating consumer-style cooking methods. To compare a double-sided grill (DSG) with a single-sided grill (SSG), two different cooking methods were used for the SSG: for the one-turnover (OT-SSG) method, a patty was turned once when the internal temperature reached 40°C, and for the multiturnover (MT-SSG) method, a patty was turned every 30 s. Patties (100 g, n = 9) inoculated with a five-strain mixture of E. coli O157: H7 at a concentration of 107 CFU/g were cooked until all three temperature readings (for two sides and the center) for a patty were 71.1°C. The surviving E. coli O157:H7 cells were enumerated on sorbitol MacConkey (SMAC) agar and on phenol red agar base with 1% sorbitol (SPRAB). The order of the cooking methods with regard to the cooking time required for the patty to reach 71.1°C was as follows: DSG (2.7 min) < MT-SSG (6.6 min) < OT-SSG (10.9 min). The more rapid, higher-temperature cooking method was more effective (P < 0.01) in destroying E. coli O157:H7 in ground beef. E. coli O157:H7 reduction levels were clearly differentiated among treatments as follows: OT-SSG (4.7 log10 CFU/g) < MT-SSG (5.6 log10 CFU/g) < DSG (6.9 log10 CFU/g). Significantly larger numbers of E. coli O157:H7 were observed on SPRAB than on SMAC agar. To confirm the safety of ground beef cooked to 71.1°C, additional patties (100 g, n = 9) inoculated with lower concentrations of E. coli O157:H7 (103 to 104 CFU/g) were tested. The ground beef cooked by the OT-SSG method resulted in two (22%) of nine samples testing positive after enrichment, whereas no E. coli O157:H7 was found for samples cooked by the MT-SSG and DSG methods. Our findings suggest that consumers should be advised to either cook ground beef patties in a grill that cooks the top and the bottom of the patty at the same time or turn patties frequently (every 30 s) when cooking on a grill that cooks on only one side.

Thermal Inactivation of Escherichia coli O157: H7, Salmonella senftenberg, and Enzymes with Potential as Time-Temperature Indicators in Ground Beef

1997 ◽  
Vol 60 (5) ◽  
pp. 471-475 ◽  
Author(s):  
ALICIA ORTA-RAMIREZ ◽  
JAMES F. PRICE ◽  
YIH-CHIH HSU ◽  
GIRIDARAN J. VEERAMUTHU ◽  
JAMIE S. CHERRY-MERRITT ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Thermal Inactivation ◽  
Ground Beef ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Triose Phosphate ◽  
Beef Products ◽  
Z Value ◽  
D Values ◽  
Salmonella Senftenberg

The USDA has established processing schedules for beef products based on the destruction of pathogens. Several enzymes have been suggested as potential indicators of heat processing. However, no relationship between the inactivation rates of these enzymes and those of pathogenic microorganisms has been determined. Our objective was to compare the thermal inactivation of Escherichia coli O157:H7 and Salmonella senftenberg to those of endogenous muscle proteins. Inoculated and noninoculated ground beef samples were heated at four temperatures for predetermined intervals of time in thermal-death-time studies. Bacterial counts were determined and enzymes were assayed for residual activity. The D values for E. coli O157:H7 were 46.10, 6.44, 0.43, and 0.12 min at 53, 58, 63, and 68°C, respectively, with a z value of 5.60°C. The D values for S. senftenberg were 53.00, 15.17, 2.08, and 0.22 min at 53, 58, 63, and 68°C, respectively, with a z value of 6.24°C. Apparent D values at 53, 58, 63, and 68°C were 352.93, 26.31, 5.56, and 3.33 min for acid phosphatase; 6968.64, 543.48, 19.61, and 1.40 min for lactate dehydrogenase; and 3870.97, 2678.59, 769.23, and 42.92 min for peroxidase; with z values of 7.41,3.99, and 7.80°C, respectively. Apparent D values at 53, 58, 63, and 66°C were 325.03, 60.07, 3.07, and 1.34 min for phosphoglycerate mutase; 606.72, 89.86, 4.40, and 1.28 min for glyceraldehyde-3-phosphate dehydrogenase; and 153.06, 20.13, 2.25, and 0.74 min for triose phosphate isomerase; with z values of 5.18, 4.71, and 5.56°C, respectively. The temperature dependence of triose phosphate isomerase was similar to those of both E. coli O157 :H7 and S. senftenberg, suggesting that this enzyme could be used as an endogenous time-temperature indicator in beef products.

Inactivation of Escherichia coli O157:H7 in Nonintact Beefsteaks of Different Thicknesses Cooked by Pan Broiling, Double Pan Broiling,or Roasting by Using Five Types of Cooking Appliances

2010 ◽  
Vol 73 (3) ◽  
pp. 461-469 ◽  
Author(s):  
CANGLIANG SHEN ◽  
JEREMY M. ADLER ◽  
IFIGENIA GEORNARAS ◽  
KEITH E. BELK ◽  
GARY C. SMITH ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Thermal Inactivation ◽  
Sodium Tripolyphosphate ◽  
Cooking Methods ◽  
Escherichia Coli O157 ◽  
Target Temperature ◽  
Pathogen Inactivation ◽  
Total Water ◽  
E Coli ◽  
George Foreman

This study compared thermal inactivation of Escherichia coli O157:H7 in nonintact beefsteaks of different thicknesses by different cooking methods and appliances. Coarsely ground beef was inoculated with rifampin-resistant E. coli O157:H7 (eight-strain composite, 6 to 7 log CFU/g) and then mixed with sodium chloride (0.45%) plus sodium tripolyphosphate (0.23%); the total water added was 10%. The meat was stuffed into bags (10-cm diameter), semifrozen (−20°C, 6 h), and cut into 1.5-, 2.5-, and 4.0-cm-thick steaks. Samples were then individually vacuum packaged, frozen (−20°C, 42 h), and tempered (4°C, 2.5 h) before cooking. Partially thawed (−2 ± 1°C) steaks were pan broiled (Presto electric skillet and Sanyo grill), double pan broiled (George Foreman grill), or roasted (Oster toaster oven and Magic Chef standard kitchen oven) to a geometric center temperature of 65°C. Extent of pathogen inactivation decreased in order of roasting (2.0 to 4.2 log CFU/g) > pan broiling (1.6 to 2.8 log CFU/g) ≥ double pan broiling (1.1 to 2.3 log CFU/g). Cooking of 4.0-cm-thick steaks required a longer time (19.8 to 65.0 min; variation was due to different cooking appliances), and caused greater reductions in counts (2.3 to 4.2 log CFU/g) than it did in thinner samples (1.1 to 2.9 log CFU/g). The time to reach the target temperature increased in order of George Foreman grill (3.9 to 19.8 min) < Oster toaster oven (11.3 to 45.0 min) < Presto electric skillet (16.3 to 55.0 min) < Sanyo grill (14.3 to 65.0 min) < standard kitchen oven (20.0 to 63.0 min); variation was due to steak thickness. Results indicated that 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.

Thermal inactivation of Escherichia coli O157:H7, Salmonella senftenberg, and Enzymes with Potential as Time-Temperature Indicators in Ground Turkey Thigh Meat

1998 ◽  
Vol 61 (2) ◽  
pp. 171-175 ◽  
Author(s):  
GIRIDARAN J. VEERAMUTHU ◽  
JAMES F. PRICE ◽  
CARL E. DAVIS ◽  
ALDEN M. BOOREN ◽  
DENISE M. SMITH
Keyword(s):  
Escherichia Coli ◽  
Thermal Inactivation ◽  
Heat Processing ◽  
Performance Standard ◽  
Inactivation Kinetics ◽  
Escherichia Coli O157 ◽  
Phenol Red ◽  
E Coli ◽  
Death Time ◽  
Salmonella Senftenberg

The USDA Food Safety and Inspection Service has proposed to amend cooking regulations to require that any thermal process used for poultry products be sufficient to cause a 7 D reduction in salmonellae. Several enzymes have been suggested as potential indicators of heat processing in poultry, yet no relationship between the inactivation rates of these enzymes and salmonellae has been determined. The thermal inactivation kinetics of endogenous muscle proteins, Escherichia coli O157:H7 and Salmonella senftenberg were compared in ground turkey thigh meat in thermal death time studies. Bacteria counts were determined and muscle extracts were assayed for residual enzyme activity or protein concentration. D and z values were calculated using regression analysis. S. senftenberg had higher D values at all temperatures and was more heat resistant than E. coli. The z values of E. coli on Petrifilm Coliform Count plates and phenol red sorbitol agar plates were 6.0 and 5.7°C, respectively. The z values of S. senftenberg were 5.6 and 5.4°C on Petrifilm and agar, respectively. Lactate dehydrogenase (LDH) was the most heat stable protein at 64°C. LDH, glyceraldehyde-3-phosphate dehydrogenase, creatine kinase, triose phosphate isomerase (TPI), acid phosphatase, serum albumin, and immunoglobulin G had z values of 3.8, 4.3, 4.8, 5.8, 6.3, 6.7, and 8.6°C, respectively, in turkey containing 4.3% fat. The z values for TPI decreased to 5.4°C in thigh meat containing 9.8% fat. Temperature dependence of TPI was most similar to that of S. senftenberg, suggesting it might function as an endogenous time-temperature integrator to monitor adequacy of processing when a performance standard based on this pathogen is implemented.

Thermal Inactivation of Escherichia coli O157:H7 Isolated from Ground Beef and Bovine Feces, and Suitability of Media for Enumeration

1998 ◽  
Vol 61 (3) ◽  
pp. 285-289 ◽  
Author(s):  
M. ROCELLE S. CLAVERO ◽  
LARRY R. BEUCHAT ◽  
MICHAEL P. DOYLE
Keyword(s):  
Escherichia Coli ◽  
Thermal Inactivation ◽  
Ground Beef ◽  
Treatment Temperature ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Polyethylene Bags ◽  
D Values ◽  
Bovine Feces

Rates of thermal inactivation of five strains of Escherichia coli O157:H7 isolated from ground beef implicated in outbreaks of hemorrhagic colitis and five strains isolated from bovine feces were determined. Ground beef (22% fat, 10 g), inoculated with individual test strains at populations ranging from 6.85 to 7.40 log10 CFU g−1 of beef, was formed into patties (0.3 cm thick and 8.0 cm in diameter) and sealed in polyethylene bags. For each strain and treatment temperature (54.4, 58.9, 62.8, 65.6, or 68.3°C), 6 bags were simultaneously immersed into a recirculating water bath. Viable cells in patties heated for various lengths of time were enumerated by plating diluted samples on sorbitol MacConkey agar supplemented with 4-methylumbelliferyl-β-d-glucuronide (MSMA) and modified eosin methylene blue (MEMB) agar. Regardless of strain or treatment temperature, higher numbers of E. coli O157:H7 cells were generally recovered on MEMB agar than on MSMA, indicating the inferiority of MSMA as a recovery medium for quantitative determination of E. coli O157:H7 cells in heat-processed ground beef. Significantly (P ≤ 0.05) higher D values when enumeration was done using MEMB agar compared with MSMA. Mean D values for combined strain data at 54.4, 58.9, 62.8, and 65.6°C from cultures on MEMB agar were 123.90, 6.47, 0.62, and 0.20 min, respectively, whereas D values of 25.5, 5.21, 0.57, and 0.18 min were obtained at the same temperatures from cultures on MSMA. Results suggest that cooking ground beef patties to an internal temperature of 68.3°C for 40 s will inactivate at least 99.99% of E. coli O157:H7 cells; z values of 4.0 and 5.1°C were calculated from mean D values obtained from MEMB agar and MSMA, respectively, as recovery media. Differences in D values and z values existed among strains but rates of thermal inactivation do not appear to be correlated with the sources of the isolates.

Thermal Inactivation of Escherichia coli O157:H7 in Beef Treated with Marination and Tenderization Ingredients

2008 ◽  
Vol 71 (7) ◽  
pp. 1349-1356 ◽  
Author(s):  
AVIK MUKHERJEE ◽  
YOHAN YOON ◽  
KEITH E. BELK ◽  
JOHN A. SCANGA ◽  
GARY C. SMITH ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Sodium Chloride ◽  
Thermal Inactivation ◽  
Ground Beef ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Log Reduction ◽  
Weight Losses ◽  
Beef Products

Internalization of Escherichia coli O157:H7 in nonintact beef products during mechanical tenderization or during injection of marination and tenderization ingredients is of concern if such products are undercooked. This study tested organic acids (0.2% citric acid and 0.3% acetic acid), potassium and calcium salts (1.8% potassium lactate, 0.63% calcium lactate, 0.86% calcium ascorbate, and 0.23% calcium chloride), and sodium chloride (2.5%) for their influence on thermal destruction of E. coli O157:H7 in ground beef serving as a model system. Ground beef batches (700 g; 5% fat) were mixed with equal volumes (22 ml) of each treatment solution or distilled water and portions (30 g) of treated ground beef were extruded in test tubes (2.5 by 10 cm). A five-strain mixture of E. coli O157:H7 (0.3 ml; 7 log CFU/g) was introduced at the center of the sample with a pipette. After overnight storage (4°C), simulating product marination, samples were heated to 60 or 65°C internal temperature, simulating rare and medium rare doneness of beef, in a circulating water bath. At 65°C, treatments with citric and acetic acid showed greater (P < 0.05) reduction (4 to 5 log CFU/g) of E. coli O157:H7 than all the other ingredients and the control (3 to 4 log CFU/g). Sodium chloride reduced weight losses (16 to 18% compared with 20 to 27% by citric or acetic acid) and resulted in a 4-log reduction in counts during cooking to 65°C. Ingredients such as citric or acetic acid may improve thermal inactivation of E. coli O157:H7 internalized in nonintact beef products, while sodium chloride may reduce cooking losses in such products.

Thermal Inactivation of Escherichia coli O157:H7 and Non-O157 Shiga Toxin–Producing Escherichia coli Cells in Mechanically Tenderized Veal†

2014 ◽  
Vol 77 (7) ◽  
pp. 1201-1206 ◽  
Author(s):  
JOHN B. LUCHANSKY ◽  
ANNA C. S. PORTO-FETT ◽  
BRADLEY A. SHOYER ◽  
HARSHAVARDHAN THIPPAREDDI ◽  
JESUS R. AMAYA ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Shiga Toxin ◽  
Thermal Inactivation ◽  
Escherichia Coli O157 ◽  
Internal Temperature ◽  
E Coli ◽  
Log Reduction ◽  
Cooking Oil ◽  
Escherichia Coli Cells ◽  
Cooking Times

Preflattened veal cutlets (ca. 71.5 g, ca. 0.32 cm thick) were surface inoculated with ca. 6.8 log CFU/g of a multistrain cocktail of Escherichia coli O157:H7 (ECOH) or a cocktail made of single strains of serogroups O26, O45, O103, O104, O111, O121, and O145 of Shiga toxin–producing E. coli (STEC) cells and then were mechanically tenderized by passing once through a “Sir Steak” tenderizer. For each cooking time, in each of at least three trials, three inoculated and tenderized cutlets, with and without breading, were individually cooked in 15 or 30 ml of canola oil for 0.0, 0.75, 1.0, 1.25, 1.5, 1.75, or 2.25 min per side on an electric skillet set at 191.5°C. The temperatures of the meat and of the skillet were monitored and recorded using a type J thermocouple. Regardless of the breading or volume of oil used to cook the meat, the longer the cooking times, the higher was the internal temperature of the meat, along with a greater reduction of both ECOH and STEC. The average final internal temperature of the meat at the approximate geometric center ranged from 56.8 to 93.1°C. Microbial reductions of ca. 2.0 to 6.7 log CFU/g and ca. 2.6 to 6.2 log CFU/g were achieved for ECOH and STEC, respectively. Our data also revealed no differences in thermal inactivation of ECOH relative to the volume of oil used to cook nonbreaded cutlets. However, when cooking breaded cutlets, the use of more (30 ml) compared with less (15 ml) cooking oil resulted in greater reductions in pathogen numbers. To deliver about a 5.0-log reduction of ECOH and STEC, and to achieve the recommended internal temperature of 71.1°C, it was necessary to cook mechanically tenderized veal cutlets for at least 1.5 min per side on a preheated electric skillet set at 191.5°C and containing 15 ml of cooking oil. These data also established that cooking times and temperatures effective for inactivating serotype O157:H7 strains of E. coli in tenderized veal are equally effective against the additional six non-O157 Shiga toxin–producing strains investigated herein.

A Screening Method for the Isolation of Escherichia coli O157:H7 from Ground Beef

1990 ◽  
Vol 53 (3) ◽  
pp. 249-252 ◽  
Author(s):  
ANITA J. G. OKREND ◽  
BONNIE E. ROSE ◽  
BARBARA BENNETT
Keyword(s):  
Escherichia Coli ◽  
Screening Method ◽  
Agar Plate ◽  
Ground Beef ◽  
Escherichia Coli O157 ◽  
Phenol Red ◽  
E Coli ◽  
Screening Programs ◽  
Meat Samples ◽  
Incubation Method

A screening method was developed for the isolation of Escherichia coli O157:H7 from raw ground beef. Suspensions at a 1:10 dilution of beef were made in a modified EC broth with novobiocin (mEC+n; EC broth with 1.12 g/L instead of 1.5 g/L Bile salts #3 and novobiocin at 20 mg/L). The samples were macerated in a Stomacher for 2 min and either shaken at 37°C (100 RPM) for 6 h, or incubated static at 35°C for 24 h. Appropriate dilutions of the cultures were then spread plated on 150×15 mm plates of MacConkey sorbitol agar (MSA). The MSA plates were incubated at 42°C overnight. A set of two plates consisting of a deep (40 ml/plate) phenol red sorbitol agar plate with 4-methylumbelliferyl ß-D-glucuronide (PRS-MUG), and a Levine EMB agar plate with added agar for a final concentration of 3%, were gridded into 12 numbered sections. Sorbitol negative colonies were picked from the MSA plates, spread on the appropriate section of the EMB, and stabbed into the corresponding section on the PRS-MUG plate. Those cultures that were sorbitol negative and MUG negative on PRS-MUG and were typically E. coli on EMB were confirmed biochemically and serologically. By this procedure O157:H7 was isolated from 5 of 10 meat samples inoculated at 0.6 organisms/g, and 10 of 10 samples at the 5/g level using the 6 h shaken method. With the 24 h static incubation method, O157:H7 was isolated from 8 of 10 samples at the 0.6/g level and 10 of 10 at the 5/g level. Thirteen strains of O157:H7 inoculated at levels between 0.4 and 0.6/g were tested and 9 of the 13 were isolated with the 6 h method, and 13 of the 13 with the 24 h method. The method is reliable and simple enough to be used in large screening programs.

Thermal Inactivation of Escherichia coli O157:H7 in Ground Beef Supplemented with Sodium Lactate†

2003 ◽  
Vol 66 (4) ◽  
pp. 664-667 ◽  
Author(s):  
LIHAN HUANG ◽  
VIJAY K. JUNEJA
Keyword(s):  
Escherichia Coli ◽  
Thermal Resistance ◽  
Thermal Inactivation ◽  
Heating Temperature ◽  
Ground Beef ◽  
Antimicrobial Effect ◽  
Sodium Lactate ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
D Values

A study was conducted to investigate the antimicrobial effect of sodium lactate (NaL) (0, 1.5, 3.0, and 4.5%) on the survival of Escherichia coli O157:H7 in 93% lean ground beef. Samples inoculated with a mixture of four strains of E. coli O157:H7 (107 to 108 CFU/g) were subjected to immersion heating in a water bath stabilized at 55, 57.5, 60, 62.5, or 65°C. Results of statistical analysis indicated that the heating temperature was the only factor affecting the decimal reduction times (D-values) of E. coli O157:H7 in 93% lean ground beef. The change in temperature required to change the D-value (the z-value) was determined as 7.6°C. The thermal resistance of this organism was neither affected by the addition of NaL nor by the interactions between NaL and temperature. Adding NaL to ground beef to reduce the thermal resistance of E. coli O157: H7 is therefore not recommended.

Effectiveness of Two Cooking Systems in Destroying Escherichia coli O157:H7 and Listeria monocytogenes in Ground Beef Patties

2000 ◽  
Vol 63 (7) ◽  
pp. 894-899 ◽  
Author(s):  
ELAINE M. D'SA ◽  
MARK A. HARRISON ◽  
SCOTT E. WILLIAMS ◽  
MARC H. BROCCOLI
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Ground Beef ◽  
Escherichia Coli O157 ◽  
Target Temperature ◽  
Internal Temperature ◽  
E Coli ◽  
Beef Patties ◽  
Textural Quality ◽  
Rapid Temperature

A rapid, high-temperature double-sided grilling–broiling (DGB) system was compared to a single-sided broiling (SSB) system for cooking of foodservice ground beef patties to reduce microbial numbers and maintain textural quality. Patties (110g) containing either Escherichia coli O157:H7 or Listeria monocytogenes (106–7 CFU/g) were cooked to target internal temperatures of 60 or 68°C on each cooking system and immediately removed from the grills without the additional holding time at 60 or 68°C that is recommended for foodservice cooking of ground beef patties. Actual final internal temperature attained, position on the grill, degree of doneness, cooking time, after-cook weight, texture characteristics, and bacterial counts of the patties were monitored. The DGB reduced E. coli O157:H7 and L. monocytogenes populations in ground beef patties by 5.7 log10 and 5.4 log10 CFU/g, respectively, when cooked to a target temperature of 60°C (actual final internal temperature of 71.2°C) and by 6.1 log10 and 5.6 log10 CFU/g, respectively, when cooked to a target temperature of 68°C (actual final internal temperature of 75.8°C). The SSB reduced E. coli O157:H7 and L. monocytogenes populations by 1.3 log10 and 1.8 log10 CFU/g, respectively, when cooked to a target temperature of 60°C (actual final internal temperature of 62.7°C) and by 2.9 log10 and 3.6 log10 CFU/g, respectively, when cooked to a target temperature of 68°C (actual final internal temperature of 69.3°C). The DGB system effected a higher, more rapid temperature increase in patties cooked to either target temperature compared to the SSB system. This higher temperature was more effective in destroying pathogens in beef patties. Texture analyses determined that patties cooked on the DGB system had significantly higher values for springiness, adhesiveness, and product height as compared to the SSB system, and patties cooked on either system had significantly higher hardness, gumminess, chewiness, and product height values at the target temperature of 68°C as compared to 60°C.

Thermal Process Validation for Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes in Ground Turkey and Beef Products

2004 ◽  
Vol 67 (7) ◽  
pp. 1394-1402 ◽  
Author(s):  
R. Y. MURPHY ◽  
E. M. MARTIN ◽  
L. K. DUNCAN ◽  
B. L. BEARD ◽  
J. A. MARCY
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Thermal Inactivation ◽  
Ground Beef ◽  
Escherichia Coli O157 ◽  
Process Validation ◽  
E Coli ◽  
Beef Products ◽  
Air Impingement ◽  
D Values

At 55 to 70°C, thermal inactivation D-values for Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes were 19.05 to 0.038, 43.10 to 0.096, and 33.11 to 0.12 min, respectively, in ground turkey and 21.55 to 0.055, 37.04 to 0.066, and 36.90 to 0.063 min, respectively, in ground beef. The z-values were 5.73, 5.54, and 6.13°C, respectively, in ground turkey and 5.43, 5.74, and 6.01°C, respectively, in ground beef. In both ground turkey and beef, significant (P < 0.05) differences were found in the D-values between E. coli O157:H7 and Salmonella or between E. coli O157:H7 and L. monocytogenes. At 65 to 70°C, D-values for E. coli O157:H7, Salmonella, and L. monocytogenes were also significantly (P < 0.05) different between turkey and beef. The obtained D- and z-values were used in predicting process lethality of the pathogens in ground turkey and beef patties cooked in an air impingement oven and confirmed by inoculation studies for a 7-log (CFU/g) reduction of E. coli O157:H7, Salmonella, and L. monocytogenes.

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