High pressure processing inactivation of listeria innocua in minced trout (oncorhynchus mykiss)

High pressure processing is a food pasteurization process with the potential to kill microorganisms with minimal effects on the sensory quality and nutrient content of the food. The effectiveness of HPP for inactivating Listeria innocua in a muscle food model system consisting of minced trout (Oncorhynchus mykiss. ) at different salt levels (0, 1, or 3% added NaCl), and the resultant visual changes to the mince using scanning electron microscopy (SEM) was examined. A three-strain cocktail of the pathogen surrogate L. innocua. (ca. 10⁸-10⁹ cfu/g) was inoculated into fish samples, which were treated at eight pressures in the range of 150-517 MPa at 20C. Treatment at ≥. 414 MPa for 5 min achieved greater than a 4-log reduction for the Listeria strains tested. Adding salt increased the effectiveness of pressure treatment for the 414 MPa and 517 MPa treatments by an additional 2.5-log. SEM revealed evidence of cell wall deformation and collapse in pressure-treated samples, particularly at 414 and 517 MPa. This study indicates that HPP treatment could potentially be an effective nonthermal pasteurization method for certain types of cured fish products.