Scientific Publications by FDA Staff

J Food Prot 2016 Feb;79(2):253-62

Thermal and pressure-assisted thermal destruction kinetics for spores of type A Clostridium botulinum and Clostridium sporogenes PA3679.

Reddy NR, Patazca E, Morrissey TR, Skinner GE, Loeza V, Schill KM, Larkin JW

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 degrees C) and pressure (0.1 to 750 MPa) to determine their resistance. More than a 5-log reduction occurred after 3 min at 113 degrees C for spores of Giorgio-A and 69-A and after 5 min at 117 degrees C for spores of PA3679. A combination of high temperatures (93 to 121 degrees 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 degrees 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 degrees 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 degrees C. Pressure-assisted thermal D-values of Giorgio-A, 69-A, and PA3679 also decreased as temperature increased from 97 to 121 degrees 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 degrees C), increasing pressure from 600 to 750 MPa had an effect on pressure-assisted thermal D-values of PA3679 (i.e., at 117 degrees 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.