Purpose: The objective of this study was to utilize STEC surrogates to evaluate high pressure processing (HPP) as an alternative to thermal treatment to reduce STEC-7 in compliance with regulatory performance standards, with minimal effect on product quality.
Methods: A five-strain rifampicin-resistant, non-pathogenic E. coli cocktail (E. coli O157:H7 surrogates; BAA-1427, BAA-1428, BAA-1429, BAA-1430, BAA-1431), was used for inoculation. Sausages were fermented at ~108°F, and the product temperature was slowly increased to 130°F, cold showered, and chilled for 6 h in a cooler. Samples were collected post-fermentation (PF; pH 5.0), when product internal temperature reached 120°F (I-120°F), 130°F (I-130°F), and after chilling (PC). Sausages from each treatment were sliced, vacuum packaged and processed (HPP; 586 MPa) for 1 s, 1, 2, 3, 4 and 5 min. E. coli populations were enumerated on Petrifilm™ (Aerobic Plate Counts, E. coli/coliform).
Results: E. coli populations of ca. 7.4 log CFU/g were obtained in the batter subsequent to inoculation. E. coli reductions of 1.2, 1.3, 3.1 and 4.2 log CFU/g or cm2 were achieved at PF, I-120°F, I-130°F and PC, respectively. HPP resulted in E. coli reductions of 2.6, 3.2 and > 3.4 (total reductions) log CFU/cm2, at 1 s, 1 min and 2 min, respectively, in summer sausage (PC). HPP (1 s) of summer sausage that was heated to 130°F (no hold), resulted in > 6.7 log CFU/g or cm2.
Significance: Currently, manufacturers rely on thermal processing to achieve the performance standard (5.0-log reduction) for E. coli O157:H7. HPP can be utilized as an alternative non-thermal lethality treatment to obtain the required reduction of E. coli O157:H7.