Nonproteolytic Clostridium botulinum toxigenesis in cooked turkey stored under modified atmospheres

The ability of nonproteolytic Clostridium botulinum type B spores to grow and produce toxin in cooked, uncured turkey packaged under modified atmospheres was investigated at refrigeration and mild to moderate abuse temperatures. Cook-in-bag turkey breast was carved into small chunks, surface-inoculated with a mixture of nonproteolytic C. botulinum type B spores, packaged in O-2-impermeable bags under two modified atmospheres (100% N-2 and 30% CO2:70% N-2), and stored at 4, 10, and 15 degreesC. Samples were analyzed for botulinal toxin and indigenous microorganisms, as well as subjected to sensory evaluation, on days 0, 7, 14, 28, 42, and 60. Given sufficient incubation time, nonproteolytic C. botulinum type B grew and produced toxin in all temperature and modified atmosphere treatment combinations. At moderate temperature abuse (15 degreesC), toxin was detected by day 7, independent of packaging atmosphere. At mild temperature abuse (10 degreesC), toxin was detected by day 14, also independent of packaging atmosphere. At refrigeration temperature (4 degreesC), toxin was detected by day 14 in product packaged under 100% N-2 and by day 28 in product packaged under 30% CO2:70% N-2 Reduced storage temperature significantly delayed toxin production and extended the period of sensory acceptability of cooked turkey, but even strict refrigeration did not prevent growth and toxigenesis by nonproteolytic C. botulinum. At all three storage temperatures, toxin detection preceded or coincided with development of sensory characteristics of spoilage, demonstrating the potential for consumption of toxic product when spoilage-signaling sensory cues are absent.