Inactivation of bacterial spores in phosphate buffer and in vegetable cream treated with high pressures

Spores of four types of Bacillus sp. in phosphate buffer (pH 7) were treated with high pressures. Bacillus cereus spores (4x10(5)/ml) were partially inactivated using a 9 kbar treatment for 10 min at 20 degrees C. Total spore inactivation was obtained at 20 degrees C after a double treatment (2 kbar for 1 min followed by 9 kbar for 1 min). Total inactivation of Bacillus licheniformis and Bacillus stearothermophilus spores was reached after 8 kbar treatment for 3 min at 60 and 70 degrees C, respectively. Bacillus coagulans spores were partially inactivated by a 9 kbar treatment for 5 min at 70 degrees C. Truffle cream (a(W) 0.98;pH 6.8) containing 8.4x10(2) spores/g of Clostridium sporogenes P. A. was preheated at 80 degrees C and treated at 6,7,8 and 9 kbar for 5 and 10 min at 80 degrees C. Treatments of 8 and 9 kbar for 10 min completely reduced the number of inoculated spores of C. sporogenes and all Bacillus spores (4.2x10(4)/g) naturally present in the product. Eight out of ten samples treated at g and 9 kbar for 10 min and incubated at 30 degrees C for 30 days were microbially sterile while two were not. High pressure treatments were not sufficient to completely destroy C. sporogenes spores in truffle cream.