Effect of High Pressure Processing on the survival of Shiga Toxin-Producing Escherichia coli (Big Six vs. O157:H7) in ground beef

Inactivation of a diverse set of shiga toxin-producing Escherichia coli in ground beef by high pressure processing

“…4 C and reached a maximum 30 C due to compression heating. Keeping the chamber temperature low prevents thermal processes interfering with HPP inactivation kinetics (Hsu et al, 2015;Sheen et al, 2015). The chamber temperature was monitored by the built-in sensor (a Ttype thermal couple device).…”

“…The filtrate (1.0 ml), after proper decimal dilutions, was plated on E. coli/coliform Petrifilm™ (3M Microbiology Products Co., St. Paul, MN). The films were maintained at room temperature for 2 h to allow the injured cells to recover (Hsu et al, 2015(Hsu et al, , 2014 and then incubated at 37 C for 24 h. Colonies were counted with a 3M Petrifilm™ plate reader (Model 6499, 3M Health Care, 3M Center, St. Paul, MN) and converted to logarithms (base 10) of colony forming units per g (log 10 CFU/g).…”

“…HPP subjects food to an elevated pressure of 100e1000 MPa typically at temperatures below 60 C. The mechanism by which HPP inactivates foodborne pathogens include: 1) cell membrane alterations, a major factor to cause death (Moussa et al, 2009); 2) ribosome dissociation, to limit cell viability (Abe, 2007); and 3) cell structure damage or destruction (Hsu et al, 2014). There have been many studies on the use of HPP to inactivate STEC in ground beef, but most of those focused on a limited number of isolates, most of which were of the O157:H7 serovar, or a small number of non-O157:H7 isolates (Hsu et al, 2015;Jiang et al, 2015;Black et al, 2010;Schilling et al, 2009;Morales et al, 2008).…”

Development and validation of a surrogate strain cocktail to evaluate bactericidal effects of pressure on verotoxigenic Escherichia coli

“…The resistance of E. coli O157:H7 and other VTEC to heat or other environmental stresses is not generally different from that of other E. coli (Ingham et al, 2010;Large et al, 2005); however, because of the large strain-to-strain variability of the stress resistance of E. coli, strain cocktails of non-pathogenic E. coli for use in challenge studies have to be validated with cocktails of pathogenic strains (Ingham et al, 2010). Because analysis of only few strains of VTEC may overestimate the lethal effect of pressure (Hsu et al, 2015), we selected pressure-resistant trains of VTEC for use in the pathogenic cocktail from more than 100 strains of VTEC with known resistance to pressure (Liu et al, 2015). Validation of cocktails was performed in ground meat, and surviving cells as well as sublethally injured cells were enumerated.…”

“…New technologies for food preservation include high hydrostatic pressure (HP) processing, which has been adopted by the meat industry in the last few years. Pressure in the range of 200 to 600 MPa inactivates some foodborne pathogens and spoilage microorganisms to enhance food safety and to extend the storage life of the product (Considine et al, 2008;Hsu et al, 2015;Knorr, 1993;Trujillo et al, 2002). However, some strains of E. coli, including a substantial proportion of strains of VTEC, resist the application of 600 MPa in meat with minimal reduction of cell counts (Liu et al, 2012(Liu et al, , 2015.…”