Impact of sodium lactate, encapsulated or unencapsulated polyphosphates and their combinations on Salmonella Typhimurium, Escherichia coli O157:H7 and Staphylococcus aureus growth in cooked ground beef

The ability of the foodborne pathogens Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica subsp. enterica serovar Typhimurium, and Staphylococcus aureus to attach, colonize, and survive on stone fruit surfaces was investigated. Fifty microliters of bacterial suspension was spot inoculated onto the sterile intact fructoplane of whole peaches and plums. Minimum time required for initial adhesion and attachment was recorded for different surface contact times. Surface colonization patterns of the four pathogens and survival under simulated commercial export conditions also were evaluated. L. monocytogenes and Salmonella Typhimurium attached immediately to stone fruit surfaces. E. coli O157:H7 and S. aureus were visibly attached after 30 s and 1 h, respectively, of direct exposure. Holding freshly harvested stone fruit at 0.5°C to simulate cold storage conditions significantly lowered the titer of E. coli O157:H7 on plums and the titers of L. monocytogenes and Salmonella Typhimurium on stone fruit. E. coli O157:H7 and L. monocytogenes at a low inoculum level and S. aureus and Salmonella Typhimurium at high and low levels did not survive the simulated export chain conditions at titers that exceeded the minimum infectious dose. However, E. coli O157:H7 and L. monocytogenes were able to survive on stone fruit surfaces when inoculated at an artificially high level. In this case, the final titer at the end of the supply chain was higher than the infectious dose. In this laboratory experiment, E. coli O157:H7, L. monocytogenes, Salmonella Typhimurium, and S. aureus at potential natural contamination levels were unable to survive simulated export conditions.

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Growth of Salmonella Serovars, Escherichia coli O157:H7, and Staphylococcus aureus during Thawing of Whole Chicken and Retail Ground Beef Portions at 22 and 30°C

Journal of Food Protection ◽

10.4315/0362-028x-68.7.1457 ◽

2005 ◽

Vol 68 (7) ◽

pp. 1457-1461 ◽

Cited By ~ 11

Author(s):

STEVEN C. INGHAM ◽

RISHI K. WADHERA ◽

MELODY A. FANSLAU ◽

DENNIS R. BUEGE

Keyword(s):

Escherichia Coli ◽

Staphylococcus Aureus ◽

Agricultural Research ◽

Ground Beef ◽

Study Data ◽

Escherichia Coli O157 ◽

Frozen Ground ◽

Salmonella Serovars ◽

Inoculation Study ◽

And Staphylococcus Aureus

Food regulatory agencies advise against thawing frozen meat and poultry at room temperature. In this study, whole chickens (1,670 g) and ground beef (453 and 1,359 g) were inoculated with Salmonella serovars, Escherichia coli O157:H7, and Staphylococcus aureus on the surface (all products) and in the center (ground beef). After freezing at −20°C for 24 h, products were thawed at 22 or 30°C for 9 h. Pathogen growth was predicted using product time and temperature data and growth values from the U.S. Department of Agriculture Agricultural Research Service Pathogen Modeling Program 7.0 predictive models of pathogen growth. No pathogen growth was predicted for whole chicken or 1,359 g of ground beef thawed at 30°C or 453 g of ground beef thawed at 22°C. Growth (≤5 generations) was predicted for 453 g of ground beef at 30°C. Inoculation study data corroborated the predictions. No growth occurred on whole chickens or 1,359-g portions of ground beef thawed at 30°C for 9 h. Pathogen numbers increased an average of 0.2 to 0.5 log on the surface of 453-g ground beef portions thawed for 9 h at 22 or 30°C. Our results suggest that thawing ≥1,670 g of whole chicken at ≤30°C for ≤9 h and thawing >453 g ground beef portions at ≤22°C for ≤9 h are not particularly hazardous practices. Thawing smaller portions at higher temperatures and/or for longer times cannot be recommended, however. Use of values derived from the Pathogen Modeling Program 7.0 model provided realistic predictions of pathogen growth during thawing of frozen ground beef and chicken.

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Effect of Irradiation Temperature on Inactivation of Escherichia coli O157:H7 and Staphylococcus aureus†

Journal of Food Protection ◽

10.4315/0362-028x-64.10.1624 ◽

2001 ◽

Vol 64 (10) ◽

pp. 1624-1626 ◽

Cited By ~ 49

Author(s):

DONALD W. THAYER ◽

GLENN BOYD

Keyword(s):

Escherichia Coli ◽

Staphylococcus Aureus ◽

Gamma Radiation ◽

Gamma Irradiation ◽

Ground Beef ◽

Irradiation Temperature ◽

Escherichia Coli O157 ◽

E Coli ◽

And Staphylococcus Aureus

The resistance of Escherichia coli O157:H7 and Staphylococcus aureus in ground beef to gamma radiation was significantly (P < 0.05) higher at subfreezing temperatures than above freezing. Ground beef was inoculated (ca. 2 × 108 CFU/g) with five isolates of either E. coli O157:H7 or S. aureus and subdivided into 25-g samples, vacuum packaged in barrier pouches, and tempered to 20, 12, 4, 0, −4, −12, −20, −30, −40, or −76°C before gamma irradiation. The studies were repeated twice. The D10-values for both of these pathogens increased significantly at subfreezing temperatures, reaching maxima at approximately −20°C. The D10-values for E. coli O157:H7 at 4 and −20°C were 0.39 ± 0.04 and 0.98 ± 0.23 kGy, respectively. The D10-values for S. aureus at 0 and −20°C were 0.51 ± 0.02 and 0.88 ± 0.05 kGy, respectively.

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