Differences in inactivation of Escherichia coli O157:H7 strains in ground beef following repeated high pressure processing treatments and cold storage

High pressure processing (HPP) is a safe non-thermal processing method to effectively improve food safety. In this study, HPP treatment followed by cold storage was investigated to reduce Escherichia coli O157:H7 in ground beef. Experiments were conducted using ground beef contaminated with six E. coli O157:H7 strains one at a time or as a cocktail. Control and inoculated ground beef samples were HPP at 25 degrees C, 35 degrees C, and 45 degrees C, at 400 MPa and pre-determined number of pressure cycles totaling a holding time of 15 min. Optimum HPP parameters were 25 degrees C, 400 MPa at five pressure cycles of 3 min each which achieved a 5-log reduction of E. coli O157: H7 in ground beef. Storing HPP processed ground beef at 4 degrees C or -20 degrees C further decreased (P < 0.05) the E. coli O157:H7 population. An effective HPP treatment (5-log reduction) was developed that could be used post-processing to reduce the risk associated with E. coli O157:H7 contamination in ground beef. (C) 2016 Elsevier Ltd. All rights reserved.