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Escherichia coli O157:H7 and Salmonella Typhimurium Risk Assessment during the Production of Marinated Beef Inside Skirts and Tri-tip Roasts


Following the foodborne outbreak in late 1992 and early 1993 caused by E. coli O157:H7 associated
with ground beef, the safety of beef products has been highly scrutinized. In 1994, USDA�s Food
Safety and Inspection Service (FSIS) declared E. coli O157:H7 an adulterant in raw ground beef. In
1999, FSIS clarified that the public health risk of raw beef products contaminated with E. coli
O157:H7 was not limited to ground beef, but also included non-intact beef products. These nonintact beef products include beef that has been injected, mechanically tenderized, or reconstructed. <P>
Since the outbreaks of 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 information to assist the industry in assessing and minimizing
the overall risk of their processes and products. Due to FSIS�s expansion of adulteration to include
non-intact beef products, a great deal of research surrounding food safety questions have been
related to the risk associated with the production of non-intact beef. <P>
A research study conducted at Kansas State University demonstrated that blade tenderization could
transfer pathogens from the surface of beef steaks to the interior tissue. However, several gaps and
questions still remain related to the production of non-intact products, specifically related to
marinating or enhanced products. For example, does the same translocation of bacteria from
outside to inside occur during marination of beef roasts that occurs during tenderization of beef
steaks, and if so, how far do the pathogens penetrate? <P>
The importance of food safety and the emphasis of production practices to reduce pathogens are
crucial to the success of the industry. To provide additional information that establishments can use
to strengthen their food safety programs, this project evaluated the effect of inoculated marinade
used in vacuum tumbling on pathogen penetration into two different commonly marinated beef
cuts. The marinade was inoculated with S. Typhimurium and E. coli O157:H7 before the product
was enhanced by vacuum tumbling. The overall result showed that during the process of vacuum
tumbling with inoculated marinade, the microorganisms penetrated the same distance as the
marinade into the beef product. Also, the microorganisms survived in spent marinade and in beef
product while being stored under refrigerated conditions. <P>
The objective is to investigate the survival of Escherichia coli O157:H7 and Salmonella spp. in beef
marinades and the transfer of these organisms from the marinades into muscle tissue through
the process of vacuum tumbling.

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The results of the study showed that with both of the marinades S. Typhimurium and E. coli
O157:H7 penetrated throughout the entire inside skirt. After having been stored for 7 days
following tumbling, the log value of both S. Typhimurium and E. coli O157:H7 decreased for the
inside skirts. After 14 days of storage following tumbling, the log value of both S. Typhimurium and
E. coli O157:H7 continued to decrease; however, both pathogens were still detectable. <P>
The penetration of the pathogens in the tri-tip roast varied depending on the thickness of the roast.
The thicker roasts had undetectable levels of both pathogens in the geometric center; however, the
thinner tri-tip roasts had detectable levels at the geometric center. The spent marinade tested on day
0, 3, and 7 showed that the microorganisms were able to survive in the marinade at refrigerated
temperatures. <P>
Overall, the results of this study demonstrated that pathogens may penetrate into the interior of beef
skirts and tri-tips during vacuum tumbling with contaminated marinade, and that pathogens survive
during refrigerated storage of spent marinade.

Savell, Jeffrey; Muras, Tiffany; Lucia, Lisa; Harris, Kerri; Hardin, Margaret
Texas A&M University
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