title: Thermal and Pressure-Assisted Thermal Destruction Kinetics for Spores of Type A Clostridium botulinum and Clostridium sporogenes PA3679.
abstract: The purpose of this study was to determine the inactivation kinetics of the spores of the most resistant proteolytic Clostridium botulinum strains (Giorgio-A and 69-A, as determined from an earlier screening study) and of Clostridium sporogenes PA3679 and to compare the thermal and pressure-assisted thermal resistance of these spores. Spores of these strains were prepared using a biphasic medium method. C. sporogenes PA3679 spores were heat treated before spore preparation. Using laboratory-scale and pilot-scale pressure test systems, spores of Giorgio-A, 69-A, and PA3679 suspended in ACES [N-(2-acetamido)-2-aminoethanesulfonic acid] buffer (pH 7.0) were exposed to various combinations of temperature (93 to 121°C) and pressure (0.1 to 750 MPa) to determine their resistance. More than a 5-log reduction occurred after 3 min at 113°C for spores of Giorgio-A and 69-A and after 5 min at 117°C for spores of PA3679. A combination of high temperatures (93 to 121°C) and pressures yielded greater log reductions of spores of Giorgio-A, 69-A, and PA3679 compared with reduction obtained with high temperatures alone. No survivors from initial levels (>5.0 log CFU) of Giorgio-A and 69-A were detected when processed at a combination of high temperature (117 and 121°C) and high pressure (600 and 750 MPa) for <1 min in a pilot-scale pressure test system. Increasing pressure from 600 to 750 MPa at 117°C decreased the time from 2.7 to 1 min for a >4.5-log reduction of PA3679 spores. Thermal D-values of Giorgio-A, 69-A, and PA3679 spores decreased (i.e., 29.1 to 0.33 min for Giorgio-A, 40.5 to 0.27 min for 69-A, and 335.2 to 2.16 min for PA3679) as the temperature increased from 97 to 117°C. Pressure-assisted thermal D-values of Giorgio-A, 69-A, and PA3679 also decreased as temperature increased from 97 to 121°C at both pressures (600 and 750 MPa) (i.e., 17.19 to 0.15 min for Giorgio-A, 9.58 to 0.15 min for 69-A, and 12.93 to 0.33 min for PA3679 at 600 MPa). At higher temperatures (117 or 121°C), increasing pressure from 600 to 750 MPa had an effect on pressure-assisted thermal D-values of PA3679 (i.e., at 117°C, pressure-assisted thermal D-value decreased from 0.55 to 0.28 min as pressure increased from 600 to 750 MPa), but pressure had no effect on pressure-assisted thermal D-values of Giorgio-A and 69-A. When compared with Giorgio-A and 69-A, PA3679 had higher thermal and pressure-assisted thermal D-values. C. sporogenes PA3679 spores were generally more resistant to combinations of high pressure and high temperature than were the spores of the C. botulinum strains tested in this study.
authors.affiliation: U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Division of Food Processing Science and Technology, 6502 South Archer Road, Bedford Park, Illinois 60501 USA. rukma.reddy@fda.hhs.gov.
authors.forename: N Rukma
authors.initials: NR
authors.lastname: Reddy
authors.affiliation: Institute for Food Safety and Health, Illinois Institute of Technology, 6502 South Archer Road, Bedford Park, Illinois 60501 USA.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Patazca
authors.affiliation: U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Division of Food Processing Science and Technology, 6502 South Archer Road, Bedford Park, Illinois 60501 USA.
authors.forename: Travis R
authors.initials: TR
authors.lastname: Morrissey
authors.affiliation: U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Division of Food Processing Science and Technology, 6502 South Archer Road, Bedford Park, Illinois 60501 USA.
authors.forename: Guy E
authors.initials: GE
authors.lastname: Skinner
authors.affiliation: Institute for Food Safety and Health, Illinois Institute of Technology, 6502 South Archer Road, Bedford Park, Illinois 60501 USA.
authors.forename: Viviana
authors.initials: V
authors.lastname: Loeza
authors.affiliation: U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Division of Food Processing Science and Technology, 6502 South Archer Road, Bedford Park, Illinois 60501 USA.
authors.forename: Kristin M
authors.initials: KM
authors.lastname: Schill
authors.affiliation: U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Division of Food Processing Science and Technology, 6502 South Archer Road, Bedford Park, Illinois 60501 USA; University of Minnesota, 1954 Buford Avenue, 120 Learning and Environmental Sciences, St. Paul, MN 55108, USA.
authors.forename: John W
authors.initials: JW
authors.lastname: Larkin
mesh_terms: D003013:Clostridium / Q000737:chemistry / Q000254:growth & development*; D047013:Clostridium botulinum type A / Q000187:drug effects / Q000254:growth & development; D004203:Disinfection / Q000295:instrumentation / Q000379:methods*; D005516:Food Microbiology; D006358:Hot Temperature; D007700:Kinetics; D011312:Pressure; D013171:Spores, Bacterial / Q000737:chemistry / Q000254:growth & development*