GROWTH AND TOXIN PRODUCTION BY CLOSTRIDIUM-BOTULINUM ON SLICED RAW POTATOES IN A MODIFIED ATMOSPHERE WITH AND WITHOUT SULFITE

The ability of Clostridium botulinum type A or B spores to grow and pr oduce toxin on fresh raw potatoes in a modified atmosphere with or wit hout sulfite was investigated at 22 degrees C. Fresh, peeled, sliced p otatoes, untreated or dipped for 2 min into 0.7% sulfite solution and drained, were surface-inoculated at several concentration levels with a mixture of C. botulinum spores, either type A or B. They were placed in a modified atmosphere (30% N/70% CO2) within oxygen-impermeable ba gs (200 g/bag) and incubated at room temperature (22 degrees C). Toxic ity was tested on days 0, 3, 4, 5, 6, and 7. After incubation, the pot atoes were blended and centrifuged, and the Millipore-filtered superna tant fluid was injected intraperitoneally into mice, Sensory evaluatio n, except taste, was also performed. Potatoes inoculated with C. botul inum type A spores but untreated with NaHSO3 became toxic in 4 to 5 da ys, which coincided with the sensory evaluation ''unfit for human cons umption. Potatoes treated with NaHSO3 regardless of inoculum size or r esidual SO2 levels appeared acceptable for human consumption through d ay 7, even though they were toxic after 4 days of incubation. Although toxicity from type B spores occurred later and in fewer test samples than toxicity from type A, some potatoes again appeared acceptable but were toxic. Thus, although NaHSO3 markedly extended the consumer acce ptability of peeled, sliced, raw potatoes at the abuse temperature, it did not inhibit outgrowth and toxin production by C. botulinum under these conditions.