Inhibition of Clostridium Botulinum by Sodium Nitrite as Affected by Bacteriological Media and Meat Suspensions

The inhibitory effect of sodium nitrite on the outgrowth of spores of Clostridium botulinum 13983B was studied in various bacteriological media and meat suspensions. The media and meat suspensions were adjusted to pH 6.2 and heated in the presence of nitrite at 110°C for 20 min. Perigo factor was produced in Perigo-type medium (PT) and Reinforced Clostridial Medium (RCM) when heated with 20 ppm of nitrite, but not in Liver Veal Medium (LVM) and Wynne Fluid Medium (WFM) even when heated with 100 ppm of nitrite. Suspensions of 50% meat in water, prepared from under-process, normal-process and over-process meats, required 500 ppm, 150 ppm and 50 ppm of nitrite, respectively, for inhibition of outgrowth.

Dialysis removed the inhibitory activity from two of the bacteriological media (LVM and WFM) and from all meat suspensions, but not from PT and RCM media. The residual nitrite concentrations were approximately the same in all seven heated preparation (100 ppm added before heating), but the redox potential varied considerably among them. The addition of reducing agents to meat suspensions decreased the redox potential and increased the inhibitory activity but did not induce the formation of the Ferigo factor.