Abstract
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 nonproteolytic C. botulinum in chilled foods. It is generally agreed that a heating process that reduces the spore concentration by a factor of 106 is 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 nonproteolytic C. botulinum spores and to obtain an appropriate representation of parameter values suitable for use in quantitative microbial risk assessment. In total, 753 D values and 436 z values 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 503 D and 338 z values 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.IMPORTANCE In total, 753 D values and 436 z values extracted from literature sources reveal significant differences in spore heat resistance properties. On the basis of collected data, two z values have been identified, z = 7°C and z = 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 of D value determination used.
Highlights
Heat treatment is an important controlling factor that, in combination with other hurdles, is used to reduce numbers and prevent the growth of and associated neurotoxin formation by nonproteolytic C. botulinum in chilled foods
753 D values were extracted from the sources; 253 D values correspond to nonproteolytic C. botulinum type B, 375 correspond to nonproteolytic C. botulinum type E, 65 correspond to nonproteolytic C. botulinum type F, and 60 correspond to a mixture of nonproteolytic C. botulinum strains
A large data set of previously published D values for nonproteolytic C. botulinum spore inactivation during heating provides evidence for the development of mathematical models that allow general conclusions regarding heat resistance and support quantitative risk assessment for food-borne hazards
Summary
Heat 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 nonproteolytic C. botulinum in chilled foods. Over the last few decades, there has been an increasing demand from consumers in many countries for innovative, ready-toeat, minimally processed chilled foods such as complete meals, prepared salads and vegetables, pizza, sandwiches, sliced cooked meat, soups, and cakes [1, 2]. These products have many desirable properties, such as improved taste, high nutritional value, convenience, and minimal use of additives and preservatives, but simultaneously, they present challenges with regard to food safety. Identification and optimization of appropriate controls (e.g., effective heating time), based on sound science, as well
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