Joint FDA / Health Canada Quantitative Assessment of the Risk of Listeriosis from Soft-Ripened Cheese Consumption in the United States and Canada: Report. Food Directorate / Direction des aliments Health Canada / Santé Canada Center for Food Safety and Applied Nutrition Food and Drug Administration U.S. Department of Health and Human Services July 2015 Contributors Risk Assessment Team Canada United States Mark Smith Régis Pouillot William Ross Sherri Dennis Loan Nguyen Steve Gendel - Clarence Murray III Risk Management Team Canada United States Hélène Couture Vincent Bunning Jeff Farber Ted Elkin André Jean Kathy Gombas - John Sheehan - Donald Zink Risk Communication, United States Susan Cahill Information Specialist, United States Lori Papadakis Acknowledgments The following organizations and individuals are acknowledged for their contributions to this project: - Former FDA/CFSAN risk assessors and risk managers David Carlson, Richard C. Whiting and Robert L. Buchanan for their participation in the early stage of the project; - Greg Paoli for the organization of an applied training in Analytica®; - The International Dairy Foods Association (Carry Frye) for the organization of a field trip in a cheese processing facility; - Versar, Inc (David Bottimore, Kathy Coon, Stephanie Sarraino) for their organization of the peer review; - József Baranyi, James S. Dickson, Cary Frye and Ralph L. Kodell for their peer review of the draft report document and the draft model; - Angela Catford for her review and suggestions for the final draft report; - Karin Hoelzer for her help on the update of Table 4. - Sofia Santillana and Steven Duret for their help on editing the final report. - This work was supported in part by an appointment to the Research Participation Program at the Center for Food Safety and Applied Nutrition administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and the U.S. Food and Drug Administration. An Interpretative Summary of this Risk Assessment, Appendixes, Answers to public comments and the Analytica® model are available at http://www.fda.gov/Food/FoodScienceResearch/RiskSafetyAssessment/ Table of Contents Contributors ................................................................................................................................... 3 Acknowledgments........................................................................................................................... 4 Table of Contents ........................................................................................................................... 5 List of Tables .................................................................................................................................. 7 List of Figures .............................................................................................................................. 12 Abbreviations and Acronyms ....................................................................................................... 14 Mathematical / Statistical Notations ........................................................................................... 15 Summary......................................................................................................................................... 1 1. Introduction .......................................................................................................................... 17 2. Background .......................................................................................................................... 18 2.1. Recalls, Outbreaks and Sporadic Cases Associated with L. monocytogenes in Soft- Ripened Cheese ..................................................................................................................................... 18 2.2. Overview of Cheese Regulation .............................................................................................. 20 2.3. Overview of Cheese Production ............................................................................................. 22 2.4. Overview of the Cheese Industry ........................................................................................... 23 2.5. Quantitative Microbial Risk Assessment............................................................................... 25 2.6. Previous Listeria Risk Assessments ....................................................................................... 26 3. Risk Assessment Modeling .................................................................................................. 28 4. Hazard Identification ........................................................................................................... 30 5. Hazard Characterization ..................................................................................................... 35 6. Basic Processes .................................................................................................................... 40 6.1. Growth ...................................................................................................................................... 41 6.1.1. Growth in Milk and Growth in Cheese after Ripening ........................................................................ 43 6.1.2. Growth in Cheese During Processing .................................................................................................. 55 6.2. Inactivation .............................................................................................................................. 58 6.2.1. General Inactivation ............................................................................................................................. 59 6.2.2. Inactivation During Initial Ripening .................................................................................................... 59 6.2.3. Inactivation During Mitigation using a Defined Log Reduction ......................................................... 59 6.3. Partitioning and Mixing .......................................................................................................... 60 6.3.1. Partition Model .................................................................................................................................... 61 6.3.2. Mixing Model ...................................................................................................................................... 62 6.4. Contamination ......................................................................................................................... 62 6.4.1. Method ................................................................................................................................................. 65 6.4.2. Results ................................................................................................................................................. 67 6.4.3. Assumptions and Discussion ............................................................................................................... 69 6.5. Removal .................................................................................................................................... 70 6.5.1. Generality ............................................................................................................................................ 71 6.5.2. Testing Bulk Milk ................................................................................................................................ 71 6.5.3. Testing Cheese Lots ............................................................................................................................. 72 7. Exposure Assessment ........................................................................................................... 72 7.1. On Farm ................................................................................................................................... 73 7.1.1. Data and Methods ................................................................................................................................ 74 7.1.2. Dairy Silo Prevalence and Concentration for the Raw-Milk Cheese Baseline Model ......................... 78 7.2. Cheese Processing .................................................................................................................... 82 7.2.1. Mitigation ............................................................................................................................................ 83 7.2.2. Cheese Formation ................................................................................................................................ 84 7.2.3. Ripening ............................................................................................................................................... 85 7.2.4. Aging ................................................................................................................................................... 88 7.3. Transport, Marketing, and Retail .......................................................................................... 89 7.3.1. Transport and Marketing Step ............................................................................................................. 89 7.3.2. Retail .................................................................................................................................................... 90 7.4. Home ........................................................................................................................................