The control of the botulism hazard in hot‐smoked trout and mackerel
The growth and toxin production of Clostridium botulinum types B, C, E and F in hot-smoked trout and mackerel has been studied. Using whole trout which were naturally contaminated with Cl. botulinum type E it was established that salt was the major inhibiting factor; a minimum concentration of 2.5% salt-on-water phase prevented the production of toxin for 30 days when fish were stored at 10°C. When whole and minced fish were inoculated with spores of Cl. botulinum types, B, E and F at a concentration considerably higher than that found in nature (102g−1) a minimum salt concentration of 3% was required to achieve a similar effect. Further studies using trout which were inoculated with suspensions of a number of strains of Cl. botulinum containing both spores and vegetative cells (102g−1) showed that fish smoked to produce a minimal salt concentration of 3% had a safe shelf life of 30 days at 10°C and 1 day at 20°C.