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Escherichia coli O157:H7 is considered as an adulterant of raw ground beef and of otherwise non-intact beef products. Because of its inherent acid tolerance, and low infective dose (≥10 cells; Doyle et al., 1997), regulatory agencies and industry have been prompted to evaluate processes that may contribute to spread of disease through ground beef, non-intact beef, and beef products made from trimmings (NACMCF, 2002; Sporing,1999; USDA-FSIS, 1999). The United States Department of Agriculture Food Safety and Inspection Service (USDA-FSIS) conducts sampling and testing of ground beef for the presence of E. coli O157:H7 (USDA-FSIS, 2002) and, since 1999, has also tested non-intact beef products for the pathogen. USDA-FSIS (2002) defines non-intact beef products as those injected with solutions, mechanically tenderized by needling, cubing or pounding devices, or those reconstructed (or restructured) into formed entrees (i.e., s cored to incorporate marinade, or formed, reconstructed products like roasts and gyros). The processes that may introduce pathogens below the surface include chopping, grinding, flaking or mincing; in fact, any process in which the integrity of an intact cut is modified or altered could allow for introduction of a pathogen.
It can be summarized that even though at low rates, mechanical tenderization and injection of flavoring and tenderizing ingredients could potentially, even though infrequently and at low levels, internalize foodborne pathogens from the surface to the interior of products like beef steaks and roasts. If such contaminated products were considered or mistaken as intact beef and intentionally or accidentally undercooked by consumers during traditional cooking processes such as grilling, broiling and frying, then the internalized pathogen might survive and pose a safety concern to the consumers. Furthermore, the risk of pathogen survival could be higher if chemical ingredients used in marination, tenderization or restructuring formulations were protective against thermal inactivation of pathogens and could contribute to a higher risk of infection from such products. Therefore, in the present study, we evaluated the effect of certain marination, tenderization and restructuring ingredients, used in non-intact steaks and roasts, on thermal inactivation of E. coli O157:H7, when the pathogen was embedded into the meat, and when the cooking of such products by various methods was insufficient. Since internalization of pathogen and subsequent thermal inactivation could be unpredictable and non-uniform in such products, and because such pathogen internalization is established to occur, even though infrequently, we decided to examine the worst case scenario, and thus, developed a model system using ground beef to conduct the study. This allowed uniform internalization of the pathogen and thorough mixing of the ingredients into the product, and hence reliable and consistent evaluation of the effect(s) of the various ingredients and cooking processes on reduction or enhancement of thermal inactivation of inoculated E. coli O157:H7. The stated objectives for this work were: To develop modified formulations and processes for marination, tenderization and restructuring of beef steaks and roasts which will minimize risk of Escherichia coli O157:H7.
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