Efectos de las altas presiones en Bacillus Cereus

This study was envisaged to obtain information about the inactivation of Bacillus cereus (CECF 148 strain) after stress (heating and pressurizing) conditions. Three day old culture (7-8 log Units/mL, with vegetative and spore forms) was grown on a brain heart infusion (BHI). The culture (200 mL) was centrifuged and suspended in 40 mL of peptone. Aliquots of 2 mL were used for the treatments. The heating treatment was performed at 60°C, 80°C and 100°C at atmospheric pressure for 15 min, in a water-bath. For pressurization the samples were treated at 100, 200, 300, 400, 600 and 700 MPa at 30°C. The release of dipicolinic acid (DPA) was analysed and the findings showed that the highest amount of DPA released was at 400 MPa. The highest reduction of Bacillus was at 100MPa. Between 200 and 700 MPa the number of microorganisms slowly decreased. At 700 MPa the amount of Bacillus was 5 log units lower than the initial counts and this pressure was not enough to inactivate Bacillus. Our findings confirm that pressure by itself at 30 °C of temperature is not capable to inactivate totally Bacillus cereus. It means that pressurized products at 700 MPa or lower pressure and at 30°C of temperature, are only pasteurized and have to be stored refrigerated.