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

• High pressure achieved a >5-log CFU/g reduction of STEC in ground beef at 450 MPa/15 min.
• The HPP impact on the survival of “Big Six” and O157:H7 strains was compared.
• Single vs. multiple-cycle modes were evaluated – no significant advantage of multiple-cycle in lethality found.
• Dynamic temperature profiles were monitored to minimize possible thermal lethality on STEC.

High pressure processing (HPP) is a safe and effective technology for improving food safety. Non-O157:H7 Shiga Toxin-producing Escherichia coli (STEC) have been increasingly implicated in foodborne illness outbreaks and recalls, and the USDA Food Safety Inspection Service (FSIS) has designated them as adulterants in meat (e.g. ground beef). In this study we compared the inactivation of multi-isolate cocktails of E. coli O157:H7 versus the non-O157:H7 STEC “Big Six” (i.e. O26, O45, O103, O111, O121, and O145) in ground beef (83% lean) using HPP at refrigeration temperature (4–7 °C). A >5-log CFU/g inactivation of both the Big Six and O157:H7 cocktails were observed at 450 MPa for 15 min. In general, the Big Six cocktail was found more sensitive to pressure stress (p < 0.05). In contrast, HPP treatment at 250 MPa (30 min) inactivated only 2.3 log of the Big Six versus 1.0 log of O157:H7. HPP treatment at 350 MPa (30 min) inactivated 4.7 log of the Big Six vs. 3.2 log of O157:H7. Multiple-cycle HPP cycles (250 or 350 MPa, three 5 min treatments) did not result in a 5 log reduction of the non-O157:H7 or O157:H7 STEC. Our results indicate that HPP inactivation parameters which are effective for O157:H7 STEC can be used for the non-O157:H7 Big Six isolates in ground beef.