STERILIZATION OF ESCHERICHIA-COLI BY HIGH-PRESSURE

Sterilization of E. coli in foods under a high pressure was studied. E . coli cells cultivated at 37-degrees-C for 48 h were used in this stu dy, because they were more resistant to a high pressure than the young er cells. Samples in a nylon bag containing the 10(7) approximately 10 (8) cells/ml were treated under 300 MPa or 400 MPa at 20-degrees-C for 10, 15 or 30 min. E. coli was sterilized in any solution of water, 10 approximately 20% protein or 1 approximately 10% sucrose at pH 7.0 ap proximately 8.8 after 10 min under 400 MPa or at pH 4.4 approximately 5.0 after 10 min under 300 MPa. In the presence of more than 50% of so ybean oil sterilization requires 15 min under 400 MPa, as opposed to t he treatment for 10 min under 400 MPa with lard (solid oil). E. coli i n a emulsion made by mixing an oil and a protein was needed to be ster ilized under 400 MPa for 30 min. The most effect method for the steril ization was to treat bacteria solution frozen at -20-degrees-C under 2 00 MPa for 10 min.