The high-pressure sterilization establishment requires data on isobaric and isothermal destruction kinetics of baro-resistant pathogenic and spoilage bacterial spores. In this study, Clostridium sporogenes 11437 spores (10(7) CFU/ml) inoculated in milk were subjected to different pressure, temperature and time (P, T, t) combination treatments (700-900 MPa; 80-100 degrees C; 0-32 min). An insulated chamber was used to enclose the test samples during the treatment for maintaining isobaric and quasi-isothermal processing conditions. Decimal reduction times (D values) and pressure and temperature sensitivity parameters, Z(T) (pressure constant) and Z(P) (temperature constant) were evaluated using a 3 x 3 full factorial experimental design. HP treatments generally demonstrated a minor pressure pulse effect (PE) (no holding time) and the pressure hold time effect was well described by the first order model (R(2) > 0.90). Higher pressures and higher temperatures resulted in a higher destruction rate and a higher microbial count reduction. At 900 MPa, the temperature corrected D values were 9.1, 3.8. 0.73 min at 80, 90, 100 degrees C, respectively. The thermal treatment at 0.1 MPa resulted in D values 833, 65.8, 26.3, 6.0 min at 80, 90, 95, 100 degrees C respectively. By comparison, HP processing resulted in a strong enhancement of spore destruction at all temperatures. Temperature corrected Z(T) values were 16.5,16.9.18.2 degrees C at 700, 800, 900 MPa, respectively, which were higher than the thermal z value 9.6 degrees C. Hence, the spores had lower temperature sensitivity at elevated pressures. Similarly, corrected Z(P) values were 714, 588, 1250 MPa at 80, 90, 100 degrees C, respectively, which illustrated lower pressure sensitivity at higher temperatures. By general comparison, it was concluded that within the range operating conditions employed, the spores were relatively more sensitive to temperature than to pressure. (C) 2009 Elsevier Ltd. All rights reserved.