FIG. 1.

Effect of medium on the number of spores of nonproteolytic C. botulinum Eklund 17B able to survive heat treatment at 80°C and then lead to growth in the same medium at 30°C. Up to 7 × 10⁵ spores were inoculated into deoxygenated, filter-sterilized PYGS broth (⧫), PYGSL broth (□), helda bean juice (▴), broccoli juice (○), turnip juice (●), potato juice (■), and spring green juice (▵). The inoculated media were not (A) or were heated in a water bath at 80°C for 2 min (B), 10 min (C), or 100 min and then were incubated at 30°C. No growth occurred in media heated for 100 min. The lethalities of the treatments in the water bath for 2, 10, and 100 min to spores of nonproteolytic C. botulinum were equivalent to those of heat treatments at 80°C for 0.1, 5.7, and 100 min, respectively, assuming that the z value was 6°C.