Populations of aerobic mesophils and inoculated E. coli during storage of fresh goat's milk cheese treated with high pressure

Pasteurized goat's milk inoculated with Escherichia coli 405 CECT was manufactured into cheese containing 108 CFU/g. The fresh cheese was treated by combinations of pressure (400, 450, and 500 MPa), temperature (2, 10, and 25°C) and time (5, 10, and 15 min). Once treated, cheeses were stored at 2 to 4°C. Counts of surviving Escherichia coli and aerobic mesophilic bacteria were determined 1, 15, 30, and 60 days after treatment. No colonies of surviving E. coli were detected 1 day after pressurization, except in samples treated for 5 min at 25°C at pressures of 400 and 450 MPa. No surviving E. coli were detected at 15, 30, or 60 days in any case. Aerobic mesophilic bacteria counts after treatment were between 2 and 3 log CFU/g in most cases and only a slight increase during refrigerated storage could be detected in samples treated at 400 MPa.