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Updated: Jun 19, 2026

Detection of Live Escherichia coli O157:H7 Cells by PMA-qPCR
Published on: February 1, 2014
Fate of Escherichia coli O157:H7 in ground beef following high-pressure processing and freezing
E P Black1, K A Hirneisen, D G Hoover
1Department of Animal and Food Sciences, University of Delaware, Newark, DE, USA.
Aims:
The purposes of this study were to evaluate the efficacy of high pressure to inactivate Escherichia coli O157:H7 in ground beef at ambient and subzero treatment temperatures and to study the fate of surviving bacteria postprocess and during frozen storage.
Methods And Results:
Fresh ground beef was inoculated with a five-strain cocktail of E. coli O157:H7 vacuum-packaged, pressure-treated at 400 MPa for 10 min at -5 or 20 degrees C and stored at -20 or 4 degrees C for 5-30 days. A 3-log CFU g(-1) reduction of E. coli O157:H7 in the initial inoculum of 1 x 10(6) CFU g(-1) was observed immediately after pressure treatment at 20 degrees C. During frozen storage, levels of E. coli O157:H7 declined to <1 x 10(2) CFU g(-1) after 5 days. The physiological status of the surviving E. coli was affected by high pressure, sensitizing the cells to pH levels 3 and 4, bile salts at 5% and 10% and mild cooking temperatures of 55-65 degrees C.
Conclusions:
High-pressure processing (HPP) reduced E. coli O157:H7 in ground beef by 3 log CFU g(-1) and caused substantial sublethal injury resulting in further log reductions of bacteria during frozen storage.
Significance And Impact Of The Study:
HPP treatment of packaged ground beef has potential in the meat industry for postprocess control of pathogens such as E. coli O157:H7 with enhanced safety of the product.
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