Effect of sodium nitrite on outgrowth and toxinogenesis of psychrotrophic Clostridium botulinum Group II type B following an extended cooling of cooked ham

Botulism is a severe disease that still occurs sporadically in Europe and foodborne origin constitutes one of the most common forms. Foodborne botulism poisoning may occur in case of the ingestion of C. botulinum neurotoxins. Meat products could be contaminated after carcass contamination linked to inappropriate slaughtering or handling practices. Sodium nitrite (NaNO2) is commonly used in meat processing for its antimicrobial effect against Clostridium spp. In a previous study, Lebrun et al (2020) demonstrated that incorporation rates of NaNO2 ≥ 30 mg/kg prevented the outgrowth and toxinogenesis of psychrotrophic C. botulinum Group II type B in a cooked ham model subjected to thermal treatment classically used in the meat processing industry. A new experimental trial was recently performed to examine the impact of an extended cooling time on this pathogen using the same cooked ham model prepared with different NaNO2 (0, 30 and 60 mg/kg) incorporation rates. This is an important point to consider since prolonged cooling can be encountered during food processing failure or in undesirable hot spots (slowest cooling) within cooling chambers. Cured ground pork batters were inoculated with a cocktail of 3 strains of C. botulinum Group II type B at 3.5 log10 CFU/g, portioned and samples of 50 g were vacuum packed then cooked and cooled according to two different regimens i.e. an usual (10.0 hours) versus a prolonged (28.5 hours) cooling period. Cooked ham model samples were then stored under reasonably foreseeable conditions of use and storage i.e. for 14 days at 4 °C and 35 days at 8°C with a cold chain break for 1 h at 20 °C on day 21. Results indicated that cooling regimens influenced the behavior of C. botulinum Group II type B during storage of cooked ham samples. Only an ingoing amount of NaNO2 of 60 mg/kg inhibited toxinogenesis of C. botulinum Group II type B in cooked ham samples subjected to the extended cooling regimen. In comparison, 30 mg NaNO2 per kg were sufficient to prevent toxinogenesis in cooked ham cooled for 10.0 hours.