Microbial safety of supercritical carbon dioxide processes

The effect of supercritical CO2 (SC-CO2) processes on the population of Escherichia coli and Staphylococcus aureus was determined in both phosphate buffer solution and ground beef systems at 35, 42.5 and 50C/10.34, 20.67 and 31.03 MPa. Higher pressures and temperatures significantly decreased the D-values of both bacteria. No cells survived at 50C. E. coli was more resistant to SC-CO2 processes than was S. aureus in phosphate buffer solution at 35C and in ground beef at 42.5C. After applying SC-CO2 at 35C for 1 h in a phosphate buffer solution, pH values dropped from 6.6-6.8 to 3.7-3.9 at each pressure and remained relatively constant at that level for 6 h. While the count of S. aureus recovered completely after 18 h of incubation, under similar conditions E. coli did not.