Quantitative Risk Assessment For Bacillus Cereus In Wet Rice Noodle

Bacillus cereus (Bc) is the main pathogenic bacteria in rice products, widely distributing in nature. Fresh wet rice noodle is a common staple food in South China which can easily be infected by Bacillus cereus causing vomiting and diarrhea. The analysis and control of Bacillus cereus contamination in food has become one of the key contents of China National Center for Food Safety Risk Assessment (CFSA) and Chinese Center for Disease Control and Prevention (CDC).In this paper, fresh wet rice noodle in Changsha was choosen as the research samples to monitor and analysis Bacillus cereus contamination level, and conduct the quantitative risk assessment. By using the method of predictive microbiology, the prective models were built under the condition of different temperature. getting growth characteristics of Bacillus cereus in wet rice noodle. Gompertz model, Logistic model, Baranyi model and MMF model were choosen to select the optimal one for the primary level model. And Ratkwosky models were for secondary level models, a square root model of maximum specific growth rate and lag phase temperature under the influence of temperature. Monitor fresh wet rice noodles contamination with Bc in Changsha city in 2014, and make consumer investigation of fresh wet rice noodles, and analyze the data of survey data for risk assessment. Finally, integrate the predictive microbiology model, the results of the survey and Bacillus cereus epidemiological data, using @RISK6.3 to complete the quantitative risk assessment of Bacillus cereus in fresh wet rice noodles, and make suggestions for risk management.The main results are as follows:The growth of Bacillus cereus in fresh wet rice noodles was inhibited at 5℃, while at 10～35℃ it appeared in the form of a typical "S" shape. Baranyi model is selected as the primary level model; and the correlation coefficients in the Baranyi model can be used in the secondary level model; the bias factor (Bf) and the accurate factor (Af) were around 1, showing that the predictive models were scientific and reliable.The monitoring of contamination level of Bacillus cereus in wet rice showed that the total positive rate of samples was 53.21%, the positive samples average contamination level was 2.88 log CFU/g. According to the data, the positive rate and contamination levels of the summer samples, street stalls samples, and of bulk samples are relatively high. Consumer investigation results show that most of the people would like to choose fresh wet rice as breakfast (50.27%), about 1-3 times a week to eat the food in the community (48.84%), snack bar or dining room (56.59%), and eat after the purchase in 1h (71.35%).Risk assessment results showed that The probabilities of occurrence of Bc food poisoning related to rice noodle intake were 5.3% in spring,13.2% in summer and 6.6% in autumn when the risk threshold was set of 105 CFU/g; the maximum correlation of Bacillus cereus food poisoning risk factors in the three seasons are the initial contamination level, that the producers and sellers strictly control the initial contamination level is the focus of risk management.