Inhibition of Clostridium botulinum Types A and E Toxin Formation by Sodium Nitrite and Sodium Chloride in Hot-Process (Smoked) Salmon

Abstract

Sodium nitrite and NaCl were evaluated as inhibitors of outgrowth and toxin production by Clostridium botulinum types A and E in abuse-stored (25°C) hot-process salmon. Salmon steaks were brined in NaCl or NaCI plus NaN0 2 and inoculated intramuscularly with spores. Steaks were then heated in a simulated hot-smoke process to internal temperatures of 62.8 to 76.7°C (145 to 170°F) for the final 30 min of a 3-to 4-h process, packaged in oxygen-impermeable fllm and stored at 25°C. During 7 days of storage, toxin production in steaks inoculated with 10 2 spores per g was inhibited by more than 3.8% water-phase NaCl for type E and 6.1% for type A. Presence of nitrite substantially reduced the salt level required to prevent toxin production. When steaks had more than 100 ppm NaN0 2 , only 2.5% NaCl inhibited type E toxin production; 150 ppm NaN0 2 and 3.5% NaCI inhibited production of type A toxin. When storage time was lengthened to 14 days or the spore inoculum increased to lQ-4 spores per g, more salt and nitrite were required for inhibition. Residual nitrite in samples stored under refrigeration (3.3°C) did not change during 22 days of storage. Under abuse temperature (25°0, residual nitrite decreased to less than 6 ppm by the 14th day in all samples tested regardless of the original nitrite concentration.