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Effect of Iysozyme concentration, heating at 90°C, and then incubation at chilled temperatures on growth from spores of non‐proteolytic Clostridium botulinum
Author(s) -
Peck M.W.,
Fernandez P.S.
Publication year - 1995
Publication title -
letters in applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.698
H-Index - 110
eISSN - 1472-765X
pISSN - 0266-8254
DOI - 10.1111/j.1472-765x.1995.tb01005.x
Subject(s) - peck (imperial) , clostridium botulinum , spore , incubation , library science , medicine , microbiology and biotechnology , biology , biochemistry , toxin , computer science , agronomy
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 μg ml ‐1 ) was added, and the tubes were given a heat treatment equivalent to 19·8 min at 90°C, cooled, and incubated at 8°, 12°, 16° and 25°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 μg ml ‐1 ) had been added prior to heating, growth and toxin formation were observed. With lysozyme added at 50 μg ml ‐1 , growth was first observed after 68 d at 8°C, 31 d at 12°C, 24 d at 16°C, and 9 d at 25°C. Thus, in these circumstances, a heat treatment equivalent to 19·8 min at 90°C was not sufficient, on its own, to give a 6–D inactivation. A combination of the heat treatment, maintenance at less than 12°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 .