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United States Department of Agriculture

Agricultural Research Service

Research Project: DEVELOPMENT OF PREDICTIVE MICROBIAL MODELS FOR FOOD SAFETY AND THEIR ASSOCIATED USE IN INTERNATIONAL MICROBIAL DATABASES

Location: Residue Chemistry and Predictive Microbiology

Title: A probability model for enterotoxin production of Bacillus cereus as a function of pH and temperature

Authors
item Ding, Tian -
item Wang, Jun -
item Park, Myoung-Su -
item Hwang, Cheng-An
item Oh, Deog-Hwan -

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 11, 2012
Publication Date: February 1, 2013
Citation: Ding, T., Wang, J., Park, M., Hwang, C., Oh, D. 2013. A probability model for enterotoxin production of Bacillus cereus as a function of pH and temperature. Journal of Food Protection. 76(2)343-347.

Interpretive Summary: Bacillus cereus (B. cereus)is a pathogen capable of producing toxins that cause severe food poisoning. The objectives of this study were to assess the toxin production of B. cereus as affected by pH (5.0, 6.0, 7.2, 8.0, and 8.5) and storage temperatures (15, 20, 25, 30, and 35C) and develop a model to describe the probability of the toxin production. The resulting model showed that the probabilities of toxin production of B. cereus increased as the temperature increased and/or as the pH approached pH 7.0. The model described the experimental data satisfactorily and identified the pH and temperature limits for the production of B. cereus toxins. The model can be used to select product pH and storage temperatures for foods to reduce the health hazards associated with B. cereus.

Technical Abstract: Bacillus cereus is frequently isolated from a variety of foods including vegetables, dairy products, meat, and other raw and processed foods. The bacterium is capable of producing enterotoxin and emetic toxin that can cause severe nausea, vomiting and diarrhea. The objectives of this study were to assess and model the probability of enterotoxin production of B. cereus in a broth model as affected by the broth pH and storage temperature. A 3-strain mixture of B. cereus was inoculated in tryptic soy broth adjusted to pH 5.0, 6.0, 7.2, 8.0, and 8.5, and the samples were stored at 15, 20, 25, 30, and 35 degrees Celsius for 24 h. A total of 25 combinations of pH and temperature, each with 10 samples, were employed in the study. The presence of enterotoxin in broth was assayed using a commercial test kit. The percentage of positive enterotoxin production in 25 treatments was fitted with a logistic regression to develop a probability model to describe the probability of toxin production as a function of pH and temperature. The resulting model showed that the probabilities of enterotoxin production of B. cereus in broth increased as the temperature increased and/or as the broth pH approached pH 7.0. The model described the experimental data satisfactorily and identified the pH and temperature limits for the production of enterotoxin. The model could provide information for assessing food poisoning risk associated with enterotoxin of B. cereus and the selection of product pH and storage temperature for foods to reduce the hazards associated with B. cereus.

Last Modified: 10/25/2014
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