Pumpkin pies were sampled and screened for presence of Bacillus cereus. Pies were obtained from a cross-section of distribution outlets including: two major chain supermarkets, an independently owned supermarket with in-store bakery and a major chain supermarket that distributes products baked at a central distribution center. Water activity (aw) and pH were determined on each sample. B. cereus was isolated on KG agar incubated at 30 C for 24 h. Intraperitoneal injections in mice were used to determine pathogenicity of the isolates. Pumpkin pies inoculated with B. cereus were incubated at 4, 25 or 35 C. B. cereus grew well at 25 C. D-values in minutes for B. cereus in pumpkin pie were 40 at 100 C, 10.5 at 108 C, and 7 at 124 C. Under normal baking conditions, the internal temperature of the pie reaches 108 C for approximately 1 min. Therefore it appears that the spores would survive baking. Potassium sorbate (0.25%) or refrigeration temperature inhibited growth of B. cereus.

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Author notes

1Oregon Agricultural Experiment Station Technical Paper No. 5614.

2Oregon State University.

3Schwan's Sales Enterprise.