Location: Residue Chemistry and Predictive Microbiology ResearchTitle: Influence of cooling rate on growth of Bacillus cereus from spore inocula in cooked rice, beans, pasta, and combination products containing meat or poultry
|MOHR, TIMOTHY - Food Safety Inspection Service (FSIS)|
|SILVERMAN, MERYL - Food Safety Inspection Service (FSIS)|
|SNYDER, PETER - Hospitality Institute Of Technology|
Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2017
Publication Date: 3/18/2018
Citation: Juneja, V.K., Mohr, T.B., Silverman, M., Snyder, P. 2018. Influence of cooling rate on growth of Bacillus cereus from spore inocula in cooked rice, beans, pasta, and combination products containing meat or poultry. Journal of Food Protection. 81(3):430-436.
Interpretive Summary: An opportunistic bacterium, Bacillus cereus, is a significant concern to the food industry since it can cause two forms of illnesses: emetic and diarrheal. Thus, there was a need to determine safe cooling time and temperature for cooked rice, beans and pasta products and provide data for risk assessment on cooked foods. We established safe cooling rates and demonstrated that extended cooling in 15 hours or more is a public health concern. These findings will be of immediate use to the retail food service establishments and regulatory agencies to ensure the microbiological safety of the cooked rice, beans and pasta products.
Technical Abstract: The objective of this study was to assess the ability of B. cereus spores to germinate and grow in order to determine a safe cooling rate for cooked rice, beans, and pasta, rice/chicken (4:1), rice/chicken/vegetables (3:1:1), rice/beef (4:1), and rice/beef/vegetables (3:1:1). Samples were inoculated with a cocktail of four strains of heat-shocked (80C/10 min) B. cereus spores (NCTC 11143, 935A/74, Brad 1, and Mac 1) to obtain a final spore concentration of approximately 2 log CFU/g. Thereafter, samples were exponentially cooled through the temperature range of 54.5 to 7.2C in 6, 9, 12, 15, 18, and 21 h. At the end of the cooling period, samples were removed and plated on mannitol egg yolk polymyxin agar. The plates were incubated at 30C for 24 h. While the net B. cereus growth from spores in beans was < 1 log after 9 h cooling, the pathogen grew faster in rice and pasta. In combination products, the net growth was 3.05, 3.89 and 4.91 log CFU/g in rice and chicken; 3.49, 4.28 and 4.96 log CFU/g in rice and beef; 3.50, 4.20, and 5.32 CFU/g in rice, chicken and mixed vegetables; and 3.68, 4.44, and 5.25 CFU/g in rice, beef and mixed vegetables after 15, 18 and 21 h cooling, respectively. This study suggests safe cooling rates for cooling cooked rice, beans, pasta, rice/chicken, rice/chicken/ vegetables, rice/beef and rice/beef/ vegetables to guard against the hazards associated with B. cereus.