Effect of hydrodynamic pressure processing on the survival of Escherichia coli O157:H7 in ground beef

Hydrodynamic pressure processing (HDP), a novel non-thermal technology that uses a small amount of explosive (100 g) to generate a supersonic–hydrodynamic shock wave in a water filled steel container (54 L) was evaluated for inactivation of Escherichia coli O157:H7 (EHEC) in ground beef. The ground beef was inoculated with a six strain cocktail of E. coli O157:H7 at three different concentrations (103, l04 and l06 CFU/g). The following strains of E. coli O157:H7 were used in the cocktail: 3027-93, 3055-93, C7927, 43888, C9490, and green fluorescent protein-expressing E. coli O157:H7 B6-914 (GFP EC). Inoculated ground beef was wrapped in polyethylene wrap, vacuum packaged into multilayer barrier bags, heat shrunk and treated with HDP. The initial concentrations of EHEC were 1.29 × 103, 2.88 × 104, and 2.19 × l06 CFU/g. After HDP treatment, the EHEC populations were reduced (P < 0.05) to 9.12 × 102, 2.40 × 104, and 1.91 × l06 CFU/g, respectively. A similar trend was observed for GFP EC which was also enumerated from the cocktail. The GFP EC initial populations of 4.26 × l02 and 3.72 × l03 CFU/g were reduced to 3.47 × 102, and 3.09 × l03 CFU/g, respectively. Although the reduction in EHEC populations due to HDP treatment was statistically significant, the practicability of the reduction was marginal. Therefore, other hurdle parameters should be included along with the HDP treatment for more practical inactivation of EHEC in ground beef.Hydrodynamic pressure processing has been applied for many unique applications including braking of ice sheets. The authors have originally developed the method of utilizing shock waves caused by explosives for tenderization of meat and are now attempting to extend the process towards microbial inactivation. The data suggest that the treatment applied only slightly reduced the population of E. coli 0157:H7 tested and suggest to modify the process including the use of extended shock waves as well as the combination with antimicrobial agents.