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The effect of recovery medium on the estimated heat‐inactivation of spores of non‐proteolytic Clostridium botulinum
Author(s) -
Peck M.W.,
Fairbairn D.A.,
Lund Barbara M.
Publication year - 1992
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.1992.tb00749.x
Subject(s) - spore , lysozyme , clostridium botulinum , food science , microbiology and biotechnology , pasteurization , heat resistance , strain (injury) , proteolytic enzymes , yolk , biology , chemistry , biochemistry , enzyme , materials science , composite material , anatomy , toxin
Heating spores of non‐proteolytic strains of Clostridium botulinum at 85°C, followed by enumeration of survivors on a highly nutrient medium indicated a 5 decimal kill in less than 2 min. The inclusion of lysozyme or egg yolk emulsion in the recovery medium substantially increased apparent spore heat‐resistance, with as little as 0.1 μg lysozyme/ml sufficient to give an increase in the number of survivors. After heating at 85°C for 2 min between 0.1% and 1% of the spores of 11 strains (5 type B, 4 type E, 2 type F) formed colonies on medium containing 10 μg lysozyme/ml. Enumeration of survivors on a medium containing lysozyme showed that heating at 85°C for 5 min resulted in an estimated 2.6 decimal kill of spores of strain 17B (type B). These findings are important in the assessment of heat‐treatments required to ensure the safety with respect to non‐proteolytic Clostridium botulinum of processed (pasteurized) refrigerated foods for extended storage such as sous‐vide foods.