The ability of spores of nonproteolytic Clostridium botulinum to survive heat treatment and subsequently produce turbidity at 10°C in the presence of NaCl was quantified for different incubation times. Spores of nonproteolytic C. botulinum strain Eklund 17B were heated at 75°C for up to 4 min or 90°C for up to 30 min and subsequently incubated at l0°C in PYGS broth containing 1.5%. 3.0%, or 4.0% NaCl (wt/vol) with or without 10 μg hen egg white lysozyme ml-1. Heat treatment at 90°C for 30 min or incubation at 10°C in the presence of 4.0% NaCl did not prevent growth from up to 1.4 × l05 spores. Heat treatment at 90°C for 15 min and incubation in the presence of 4.0% NaCl did prevent growth in the same conditions.
Keywords: NaCl; heat; refrigeration; salt.