ABSTRACTThe effects of different media, length of time of incubation, media constituents and pH on recovery of spores ofBacillus subtilisvar.nigerexposed to hydrogen peroxide were examined. As the time of exposure of spores to hydrogen peroxide increased, the incubation time required for colony formation increased. A medium consisting of 7.5 g/L of yeast extract, 2.5g of glucose/L, 6.0g of vitamin‐free casamino acids/L, 15.0g of agar/L, 0.1g of ferrous sulfate/L, and 0.1g of manganous sulfate/L gave the best recovery. The presence of glucose and yeast extract in the medium was important Autoclaving of ferrous sulfate and manganous sulfate apart from the rest of the medium improved recovery and allowed for pH adjustment of the medium before autoclaving. Maximal recovery occurred between pH 6.8 and 7.0. The results of these experiments indicate that the sporicidal action of hydrogen peroxide may not be as great as previously observed and that careful attention should be paid to the procedures used to evaluate the safety of food processes that utilize hydrogen peroxide as a bactericid
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