title: Effect of lysozyme concentration, heating at 90 degrees C, and then incubation at chilled temperatures on growth from spores of non-proteolytic Clostridium botulinum.
abstract: The heat treatment necessary to inactivate spores of non-proteolytic Clostridium botulinum in refrigerated, processed foods may be influenced by the occurrence of lysozyme in these foods. Spores of six strains of non-proteolytic Cl. botulinum were inoculated into tubes of an anaerobic meat medium, to give 10(6) spores per tube. Hen egg white lysozyme (0-50 micrograms ml-1 was added, and the tubes were given a heat treatment equivalent to 19.8 min at 90 degrees C, cooled, and incubated at 8 degrees, 12 degrees, 16 degrees and 25 degrees C for up to 93 d. In the absence of added lysozyme, neither growth nor toxin formation were observed. A 6-D inactivation was therefore achieved. In tubes to which lysozyme (5-50 micrograms ml-1 had been added prior to heating, growth and toxin formation were observed. With lysozyme added at 50 micrograms ml-1, growth was first observed after 68 d at 8 degrees C, 31 d at 12 degrees C, 24 d at 16 degrees C, and 9 d at 25 degrees C. Thus, in these circumstances, a heat treatment equivalent to 19.8 min at 90 degrees C was not sufficient, on its own, to give a 6-D inactivation. A combination of the heat treatment, maintenance at less than 12 degrees C, and a shelf-life not more than 4 weeks reduced the risk of growth of non-proteolytic Cl. botulinum by a factor of 10(6).
authors.affiliation: Institute of Food Research, Norwich Laboratory, Norwich Reseach Park, UK.
authors.forename: M W
authors.initials: MW
authors.lastname: Peck
authors.forename: P S
authors.initials: PS
authors.lastname: Fernandez
mesh_terms: D003014:Clostridium botulinum / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology; D003080:Cold Temperature; D010450:Endopeptidases / Q000378:metabolism; D005516:Food Microbiology; D005519:Food Preservation; D006358:Hot Temperature; D009113:Muramidase / Q000494:pharmacology*; D013171:Spores, Bacterial / Q000502:physiology; D013997:Time Factors; D014118:Toxins, Biological / Q000096:biosynthesis
chemical_list: D014118:Toxins, Biological; D009113:Muramidase; D010450:Endopeptidases