title: Combined high pressure and thermal processing on inactivation of type A and proteolytic type B spores of Clostridium botulinum.
abstract: The aim of this study was to determine the resistance of multiple strains of Clostridium botulinum type A and proteolytic type B spores exposed to combined high pressure and thermal processing and compare their resistance with Clostridium sporogenes PA3679 and Bacillus amyloliquefaciens TMW-2.479-Fad-82 spores. The resistance of spores suspended in N-(2acetamido)-2-aminoethanesulfonic acid (ACES) buffer (0.05 M, pH 7.0) was determined at a process temperature of 105°C, with high pressures of 600, 700, and 750 MPa by using a laboratory-scale pressure test system. No surviving spores of the proteolytic B strains were detected after processing at 105°C and 700 MPa for 6 min. A . 7-log reduction of B. amyloliquefaciens spores was observed when processed for 4 min at 105°C and 700 MPa. D-values at 105°C and 700 MPa for type A strains ranged from 0.57 to 2.28 min. C. sporogenes PA3679 had a D-value of 1.48 min at 105°C and 700 MPa. Spores of the six type A strains with high D-values along with C. sporogenes PA3679 and B. amyloliquefaciens were further evaluated for their pressure resistance at pressures 600 and 750 MPa at 105°C. As the process pressure increased from 600 to 750 MPa at 105°C, D-values of some C. botulinum strains and C. sporogenes PA3679 spores decreased (i.e., 69-A, 1.91 to 1.33 min and PA3679, 2.35 to 1.29 min). Some C. botulinum type A strains were more resistant than C. sporogenes PA3679 and B. amyloliquefaciens to combined high pressure and heat, based on D-values determined at 105°C. Pulsed-field gel electrophoresis (PFGE) was also performed to establish whether strains with a similar restriction banding pattern also exhibited similar D-values. However, no correlation between the genomic background of a strain and its resistance to high pressure processing was observed, based on PFGE analysis. Spores of proteolytic type B strains of C. botulinum were less resistant to combined high pressure and heat (700 MPa and 105°C) treatment when compared with spores of type A strains.
authors.affiliation: Institute for Food Safety and Health, U.S. Food and Drug Administration, Illinois 60501, USA. rukma.reddy@fda.hhs.gov
authors.forename: N Rukma
authors.initials: NR
authors.lastname: Reddy
authors.forename: Kristin M
authors.initials: KM
authors.lastname: Marshall
authors.forename: Travis R
authors.initials: TR
authors.lastname: Morrissey
authors.forename: Viviana
authors.initials: V
authors.lastname: Loeza
authors.forename: Eduardo
authors.initials: E
authors.lastname: Patazca
authors.forename: Guy E
authors.initials: GE
authors.lastname: Skinner
authors.forename: Kathiravan
authors.initials: K
authors.lastname: Krishnamurthy
authors.forename: John W
authors.initials: JW
authors.lastname: Larkin
mesh_terms: D001407:Bacillus / Q000502:physiology; D003013:Clostridium / Q000502:physiology; D003014:Clostridium botulinum / Q000502:physiology*; D015169:Colony Count, Microbial; D005516:Food Microbiology; D005519:Food Preservation / Q000379:methods*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D006874:Hydrostatic Pressure; D050296:Microbial Viability; D013171:Spores, Bacterial / Q000254:growth & development