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Evaluation of Different Temperatures and Dwell Times of Hot Water to Achieve Maximum Effectiveness in Reducing Levels of Salmonella Typhimurium, Escherichia coli O157:H7 and Coliforms/Escherichia coli on Beef Carcass Surfaces


The beef industry continues to be challenged with recalls and illnesses associated with Escherichia coli
O157:H7. S ince 1993, beef producers and packers have spent more than $420 million dollars on
beef safety research. These investments have resulted in the publication of a significant amount of
research data, best practices and guidelines to assist the beef industry in assessing the overall risk of
their processes and products. An additional challenge comes in finding and applying the best
practices and parameters to fit such a wide range of plant sizes, products, process capabilities and yet
remain cost effective. While hot water continues to be an effective antimicrobial intervention, for
beef carcasses, primals and trim, whether applied alone or in combination with an organic acid,
issues arise in defining how �hot is hot� and in narrowing down appropriate water versus surface
temperature. In addition, questions often arise as to the minimum temperature that must be
achieved for the hot water treatment to still be effective in reducing levels of the pathogens of
concern for the beef industry. This also brings to bear the real world application of antimicrobial
interventions and the specific ability of a processor to achieve the pressure, dwell times and
temperatures such as those published in the scientific literature and as they related to different types
of carcass surfaces (fat and lean). Temperatures and dwell times applied in a plant situation may
vary with the facility�s in-house hot water capability (and sustainability) and worker safety, as well as
with desired line speed and available space on the line for a pre-fabricated final wash cabinet. <P>
Both Salmonella and E. coli O157:H7 are human pathogens and natural inhabitants of cattle.
Although E. coli O157:H7 has been associated with fewer reported illnesses when compared to
Salmonella, the severity of the illness, with the development of hemolytic uremic syndrome, and the
case mortality rate, particularly for immunocompromised individuals, is significantly higher than for
Salmonella. The presence of these organisms in cattle at slaughter and in associated products, poses
poses a risk in raw beef products from both a public health and a regulatory perspective. <P>
The objectives of this project were to determine the potential of hot water applied over varying
exposure times and temperatures to reduce the levels of Salmonella Typhimurium, Escherichia coli
O157:H7 and coliforms/Escherichia coli on beef carcass surfaces and to evaluate the effect of varying
exposure times and temperatures of hot water on meat surface type (fat and lean).

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Findings: There were no differences (P > 0.05) in the log reductions of S. Typhimurium and E. coli O157:H7
on the lean surfaces on the inside round for all three temperature treatments (66, 74, and 82°C).
Although the 15 s treatment resulted in a numerically higher log reduction (Table 1) than the 5 and
10 s treatments, each of the times resulted in at least a 1 log reduction of both S. Typhimurium and
E. coli O157:H7 for lean surfaces of inside rounds. For the fat surfaces of the beef outside round all
three time treatments for the 82°C and the 10 and 15 s treatments for the 74°C resulted in the
highest log reduction for S. Typhimurium. The 5 and 10 s dwell times for treatments at 66°C and
the 5 s dwell time at 74°C resulted in the lowest log reduction of S. Typhimurium and E. coli
O157:H7. The only time and temperature treatment for the fat surfaces of the outside round that
did not result in at least a 1 log reduction for S. Typhimurium was the 66°C for 5 s treatment. For E.
coli O157:H7 all temperature and time treatments resulted in at least a 1 log reduction for the fat
surfaces of the outside round. These data show that as the water temperature increased the lean
surfaces had a higher color recovery value; however, for all treatments the 24 h post treatment color
of the lean surfaces was still acceptable. For the fat surfaces there were no differences (P > 0.05) for
24 h post treatment color recovery for any of the temperature treatments.

Savell, Jeffrey; Harris, Kerri; Hardin, Margaret; Castillo, Alejandro
Texas A&M University
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