Thermal inactivation of Escherichia coli was studied under CO 2 pressures of 1.2, 2.5, and 5 MPa at 25, 35, and 45ЊC. Two phases were observed in the destruction curves. The earlier stage was characterized by a slow rate of inactivation, which increased sharply at the later stage. An increase of pressure and/or temperature enhanced the antimicrobial effects of CO 2 under pressure. The effects on cell structure were studied by scanning electron microscopy and the specific mechanism of action appeared to be related to enzyme inactivation.