A risk assessment study of Bacillus cereus present in pasteurized milk

Due to the heat resistance of Bacillus cereus, its potential pathogenic character, the capability to grow in milk and reported diseases upon consumption of dairy products, the organism should be considered as hazardous in pasteurized milk. Human exposure experiments based on (1) enquiring about the storage conditions (time and temperature) of pasteurized milk in households in The Netherlands and (2) performing of storage tests at 6, 8, 10 and 12 degree C, respectively, demonstrated the following: pasteurized milk is consumed within 2-12 days after pasteurization and is stored at temperatures varying from 10 super(5) and > 10 super(6) B. cereus ml super(-1), respectively. Taking into account the high portion of milk consumed (approximately 10 super(9)-10 super(10) portions/year) and the absence of epidemiological evidence that milk is causing foodborne diseases due to B. cereus, the dose-response relationship of this organism may need to be considered. Results of the storage tests, based on the worst case situation, provided useful information on the effect of the risk factors, storage temperature and time, to human exposure. However, such information can be obtained more easily by applying predictive models. Models also enable us to find out the initial number of spores which can be considered as a third risk factor.