Effect of Sugar and Low-Dose Irradiation on Toxin Production by Clostridium botulinum in Comminuted Bacon

Comminuted bacon, processed to contain target levels of 40 μg NaNO₂/g and 0, 0.25 or 0.75% sucrose or 0.75% glucose, was inoculated with a mixture of spores of 20 strains of Clostridium botulinum (400 spores per g) and was canned under vacuum. Portions were irradiated using ¹³⁷Cs at doses of 0, 0.19, 0.38, 0.75, 1.12 and 1.5 Mrad. Cans were incubated for 1, 2, 4 or 8 wk at 30°C. Some cans of nonirradiated bacon without or with 0.25% sucrose became toxic in 2 wk; with 0.75% sucrose, toxin production was delayed to 8 wk. Bacon irradiated at 0.75 Mrad, made with or without sucrose, became toxic in 2 to 4 wk, whereas most cans of bacon irradiated at 1.5 Mrad remained toxin-free for the 8-wk incubation period. A comparison of bacon made with 0.75% sucrose or glucose showed no difference between the sugars in the rates of toxin production by C. botulinum in irradiated cans of bacon. Irradiation at 0.19 Mrad increased the rate of toxin formation over nonirradiated bacon in sugar-containing (0.75%) bacon, but had no effect in sugar-free bacon. The pH of nonirradiated bacon containing 0.75% glucose or sucrose decreased from pH 6.12 and 6.11, respectively, to pH 5.63 and 5.67 after 8 wk of incubation at 30°C. The titratable acidity showed a concurrent increase. The pH and titratable acidity of bacon irradiated at 0.19 Mrad or higher showed no changes.