Growth Profile and Toxigenicity of Bacillus cereus in Ready-to-eat Food Products of Animal Origin

The growth profile of Bacillus cereus in ready-to-eat (RTE) food products of animal origin was examined under different temperature and incubation conditions. In sandwiches and Kimbab, B. cereus did not grow or exhibited only minimal growth at 4 and 10oC, but it grew rapidly at ambient temperature. In sandwiches, B. cereus did not grow efficiently at 25oC, however, in ham, the main ingredient of sandwiches, B. cereus growth was observed at the same temperature, with bacterial levels reaching 7.94 Log CFU/g after incubation for 24 h at 25oC. Toxigenicity of B. cereus was observed only at temperatures above 25oC. In Kimbab, B. cereus produced toxin after 9 h at 30oC and after 12 h at 25oC. Ingredients of sandwiches and Kimbab were collected from 3 different Korean food-processing companies to investigate the source of contamination by B. cereus. Among the 13 tested food items, 6 items including ham were found to be contaminated with B. cereus. Of these ingredients, B. cereus isolates from 3 items produced enterotoxins. None of these isolates harbored the emetic toxin-producing gene. The findings of the present study can be used for risk assessments of food products, including ham and cheese, contaminated with B. cereus.