Contribution of Nitrite to the Control of Clostridium botulinum in Liver Sausage

Liver sausage was formulated with different brine and nitrite concentrations, challenged with a mixture of spores of five strains each of Clostridium botulinum , types A and B at 10-fold increasing concentrations, temperature-abused at 27°C, and assayed for botulinal toxin after various periods. From the number of toxic sausages and initial spore concentrations, the probability (P) of a single spore to give rise to toxin within a given period of abuse was estimated. At moderate brine concentrations (3.8-4.2% salt), 50 or 100 ppm of nitrite had little or no effect on toxigenesis; the estimated P values for one week at 27°C were from 10^-2 to 10^-4 with 0 and 50 ppm of nitrite, and from 10^-2 to 10^-5 with 100 ppm. With 150 ppm, however, P was consistently <2 × 10^-6 At a higher brine concentration, an appreciable delay in toxigenesis was also obtained with 50 or 100 ppm of nitrite. Randomly typed extracts from 44 toxic sausages all contained C. botulinum type A toxin only. At toxin levels ≥100 mouse MLD/g the sausages had a putrid odor, but sausages with less toxin often appeared organoleptically acceptable. Storage of sausages at 8°C for 6 weeks before incubation at 27°C resulted in nearly complete disappearance of detectable nitrite, but did not diminish the inhibitory effect of the initial nitrite. Increased processing temperature and/or prolonged time of processing reduced the inhibitory effect of nitrite.