Title: Translocation and thermal inactivation of Shiga toxin-producting Escherichia coli in blade tenderized and/or vacuum tumbled beef Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 15, 2013
Publication Date: May 28, 2013
Citation: Foster-Bey, L., Shane, L., Shoyer, B.A., Luchansky, J.B., Porto Fett, A.C. 2013. Translocation and thermal inactivation of Shiga toxin-producting Escherichia coli in blade tenderized and/or vacuum tumbled beef. Meeting Abstract.STEC Coordinated Agricultural Project Annual Meeting, May 28-30, 2013, Lincoln,Nebraska. Volume 1, Page 1. Technical Abstract: Foodborne pathogens, such as Shiga toxin-producing Escherichia coli (STEC), a natural inhabitant on raw meat, may be transferred from the surface of the meat into the deeper layers of tissue following enhancement by blade tenderization and vacuum tumbling. Therefore, the consumption of enhanced beef, cooked to a rare to medium rare (lower than 140 deg F; lower than 60 deg C) degree of doneness, may pose a significant public health risk, since the temperature achieved within the meat may not be sufficient to eliminate cells of STEC internalized via the enhancement processes. Thus, the goal of this research was to quantify translocation of STEC into beef subprimals following enhancement, and then to determine the effect of grilling on the fate of the internalized STEC. In phase I, boneless beef subprimals were inoculated (ca. 6.5 log CFU per g) on the lean side with a rifampin-resistant cocktail comprised of single strains from each of eight target serogroups of STEC (STEC-8; O111:H-, O45:H2, O103:H2, O104:H4, O121:H19, O145:NM, O26:H11, and O157:H7). Briefly, inoculated subprimals were blade tenderized (BT), or vacuum tumbled (VT), or blade tenderized and then vacuum tumbled (BT/VT). For the BT treatment, inoculated subprimals were passed once through a mechanical tenderizer with the lean-side facing up. For the VT treatment, subprimals were tumbled for 15 min at 21 deg C, at a speed of 20 rpm and at a vacuum pressure of minus 0.85 bar in a vacuum tumbler. Lastly, for the BT/VT treatment, subprimals were blade tenderized and then vacuum tumbled as described above. In each of two trials, ten core samples were removed from each subprimal and cut into six consecutive segments: segments 1 to 4 comprised the top 4 cm and segments 5 and 6 the deepest 4 cm. In phase II, the fate of STEC-8 within enhanced subprimals was quantified following cooking. Enhanced subprimals were cut into 1.25 inch steaks and then cooked to a target internal temperature of 120 deg F (48.9 deg C), 140 deg F (60 deg C), or 160 deg F (71.1 deg C) on an electric clam-shell grill set at 375 deg F (190.5 deg C). In each of two trials, three steaks were analyzed at each of the three cooking temperatures for each of the three enhancement treatments tested. Regarding translocation, regardless of the enhancement treatment, the majority (9.9 to 23.3%) of the STEC-8 cells were internalized within the top 1 cm of the beef. Regarding cooking, as expected, the higher the cooking temperature, the greater the reduction of STEC. Regardless of the enhancement treatment, when steaks were cooked to target internal temperatures of 120 deg F to 160 deg F we observed a 3.0 to 4.4-log CFU reduction in pathogen numbers. Our results revealed that regardless of how steaks were enhanced, STEC-8 were translocated into the deeper tissues of the subprimal and cooking was effective to reduce appreciable levels of STEC.