ABSTRACTHeat treatment is an important controlling factor that, in combination with other hurdles (e.g., pH, aw), is used to reduce numbers and prevent the growth of and associated neurotoxin formation by nonproteolyticC. botulinumin chilled foods. It is generally agreed that a heating process that reduces the spore concentration by a factor of 106is an acceptable barrier in relation to this hazard. The purposes of the present study were to review the available data relating to heat resistance properties of nonproteolyticC. botulinumspores and to obtain an appropriate representation of parameter values suitable for use in quantitative microbial risk assessment. In total, 753Dvalues and 436zvalues were extracted from the literature and reveal significant differences in spore heat resistance properties, particularly those corresponding to recovery in the presence or absence of lysozyme. A total of 503Dand 338zvalues collected for heating temperatures at or below 83°C were used to obtain a probability distribution representing variability in spore heat resistance for strains recovered in media that did not contain lysozyme.IMPORTANCEIn total, 753Dvalues and 436zvalues extracted from literature sources reveal significant differences in spore heat resistance properties. On the basis of collected data, twozvalues have been identified,z= 7°C andz= 9°C, for spores recovered without and with lysozyme, respectively. The findings support the use of heat treatment at 90°C for 10 min to reduce the spore concentration by a factor of 106, providing that lysozyme is not present during recovery. This study indicates that greater heat treatment is required for food products containing lysozyme, and this might require consideration of alternative recommendation/guidance. In addition, the data set has been used to test hypotheses regarding the dependence of spore heat resistance on the toxin type and strain, on the heating technique used, and on the method ofDvalue determination used.
Systematic Assessment of Nonproteolytic Clostridium botulinum Spores for Heat Resistance
