Effects of High Hydrostatic Pressure and Beef Patty Formulations on the Inactivation of Native Strains of Shiga Toxin-Producing Escherichia coli O157:H7

This study aimed to evaluate the effects of beef patty formulations and pressure levels on the inactivation of spoilage microbiota and native Shiga toxin-producing Escherichia coli (STEC) O157:H7. Beef patties were made with different salt and fat content (A: 1% NaCl – 10% fat, B: 2% NaCl – 10% fat, C: 1% NaCl – 20% fat and D: 2% NaCl – 20% fat) and treated at 400 and 600 MPa. STEC reductions after 400 and 600 MPa were 2 and 4 log CFU/g, respectively. STEC inactivation was similar in patties with 10 and 20% of fat content. However, patties with 1% of NaCl showed higher STEC reductions than those made with 2% of NaCl. The baroprotective effect of salt was probably related with the accumulation of compatible solutes, a well-known bacterial response to osmostress. After HPP treatment, all counts of spoilage microbiota were under the detection limit regardless of the formulation.