Effect of high hydrostatic pressure on Escherichia coli and Pseudomonas fluorescens strains in ovine milk

Ovine milk that had been standardized to 6% fat was inoculated with Escherichia coli 405 CECT and Pseudomonas fluorescens 378 CECT at a rate of 10(6) and 10(7) cfu/ml, respectively, and treated with high hydrostatic pressure. Treatments consisted of combinations of pressure (300, 400, 450, and 500 MPa), temperature (2, 10, 25, and 50 degrees C), and time (5, 10, and 15 min). Inactivation (>6 log cfu/ml) of both strains was observed at 50 degrees C for all pressures and treatment times. A similar level of inactivation occurred at greater than or equal to 450 MPa and 25 degrees C for E. coli and at greater than or equal to 400 MPa and 10 degrees C for P. fluorescens. Destruction was lowest at 10 degrees C for E. coli and at 25 degrees C for P. fluorescens. The test strain of E. coli was more baroresistent than was the P. fluorescens strain.