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 10℃, but it grew rapidly at ambient temperature. In sandwiches, B. cereus did not grow efficiently at 25℃, 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 25℃. Toxigenicity of B. cereus was observed only at temperatures above 25℃. In Kimbab, B. cereus produced toxin after 9 h at 30℃ and after 12 h at 25℃. 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.