Thermal Death of Bacillus subtilis Spores in Oil-Water Systems

The thermal death of the spores of Bacillus subtilis 168 in oil-water systems including emulsions and separated layers consisting of phosphate buffer and soybean oil or n-hexadecane was investigated. The resultant survivor curve consisted of two phases, an initial rapid reduction followed by a slow reduction, possibly as reflected by the death in the water phase and the oil phase, respectively. The concentration of oil in the system strikingly affected the pattern of thermal death. These results suggest that the spore location in the oil-water system may be a critical factor in determining the heat resistance.