TABLE 2.

Wet-heat inactivation and DPA release parameters for spores from Bacillus strains 168, A163, and IC4a

ParameterValue for strain:EquationFigure(es)
168A163IC4
D 98 (min)1831A
D 105 (min)1.431A
D 111 (min)0.22231A, 1B
D 115 (min)2.631B
D 120 (min)0.731B
D 121 (min)3.2 (22)31C
D 126 (min)1.0 (4.1)31C
D 131 (min)0.3 (0.8)31C
N 0 1.3 × 1065.7 × 1052.8 × 10511A, 1B, 1C
Nr 13089011A, 1B, 1C
Z (°C)6.36.19.7 (7.3)31A, 1B, 1C
A 1 (%)14239.543
ΔT (°C)1.52.52.743
Tc (°C)10812113143
  • a The D and Z values, as well as the parameters N0 and Nr for spores from strains 168, A163, and IC4, result from fitting equations 1 and 3 to the data points in Fig. 1 (fits shown). For comparison the DPA release parameters of the sigmoidal fits (equation 4) shown in Fig. 2 for spores from the same strains have been indicated in the lower part of the table. The D value is the decimal reduction value with the inactivation temperature in the subscript; Nr is the heat-resistant rest population; N0 plus Nr equals the number of viable spores at time zero; A1 is the minimum percentage of DPA released, and A2 the maximum, fixed at 100%; Tc is the center at (A1 + A2)/2 and ΔT the associated temperature range. The Dr and Zr values of the heat-resistant fraction Nr of IC4 spores are given in parentheses. It should be noted that the uncertainty in the Dr121, Dr131, and Zr values is very large.