ARS | Publication request: Thermal inactivation of shiga toxin-producing 0157:H7 (ECOH) and non-0157:H7 shiga toxin-producing (STEC) Escherichia coli cells in wafers of ground beef

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 6, 2012
Publication Date: July 22, 2012
Citation: Luchansky, J.B., Porto Fett, A.C., Shoyer, B.A., Phillips, J.G., Eblen, D., Kause, J., Evans, P., Shaw, W., Bauer, N. 2012. Thermal inactivation of shiga toxin-producing 0157:H7 (ECOH) and non-0157:H7 shiga toxin-producing (STEC) Escherichia coli cells in wafers of ground beef [abstract]. July 22-25, 2012, Providence, Rhode Island. 1:1.

Technical Abstract: Escherichia coli O157:H7 (ECOH) and six other highly pathogenic serotypes of Non-Shiga toxin producing E. coli (STEC) are adulterants in ground/non-intact raw beef. However, it is not known if validated thermal interventions for ECOH in raw beef would also be effective for inactivating STEC. The objective of this study was to quantify the effect of heat on the fate of ECOH and STEC in a model beef system. For each of two trials, freshly-ground beef of higher (70:30 = percent lean:fat) or lower (93:7 = percent lean:fat) fat content was inoculated separately with a single strain of E. coli serotypes O111:H-, O45:H2, O103:H2, O121:H19, O145:NM, O26:H11, and O157:H7 to ca. 7.0 log CFU/g. Next, 3-g samples were transferred into filter bags. With the aid of a stainless-steel roller, the meat was flattened (about 1.0 mm) within the bags and then vacuum-sealed. For each target temperature and time point, three bags were submerged in a thermostatically-controlled water bath and heated to an internal temperature of 54.4 degree Celsius for up to 90 min, or 60 degree Celsius for up to 4 min, or 65.6 degree Celsius for up to 0.5 min. Note, the safe cooking guidance for raw beef products generally is above 62.8 degree Celsius. D-values decreased as the heating temperature increased. In lower fat wafers, D-values ranged from 13.7 to 23.8 min, 0.86 to 1.33 min, and 0.19 to 0.22 min at 54.4 degree Celsius, 60 degree Celsius, and 65.6 degree Celsius, respectively. Heating higher fat wafers to 54.4 degree Celsius, 60 degree Celsius, or 65.6 degree Celsius generated D-values of 20.4 to 32.7 min, 0.83 to 1.22 min, and 0.18 to 0.34 min, respectively. In general, with the exception of wafers heated to 54.4 degree Celsius, no effect of fat level on lethality of STEC and ECOH and no appreciable differences in thermal inactivation among STEC serotypes and between STEC and ECOH were observed. These data established that cooking times/temperatures effective for inactivating ECOH in ground beef are equally effective against the additional STEC strains investigated.