T10-02 Farm to Fork Quantitative Microbial Risk Assessment for Norovirus on Frozen Berries

Wednesday, July 12, 2017: 8:45 AM
Room 16 (Tampa Convention Center)
Robyn Miranda , Rutgers University , New Brunswick , NJ
Donald W. Schaffner , Rutgers University, Department of Food Science , New Brunswick , NJ
Introduction: Frozen fruit has been linked to Norovirus outbreaks throughout the world. Contamination sources on the farm have been attributed to the use of contaminated irrigation water and infected food handlers. A quantitative microbial risk assessment describing Norovirus prevalence and concentration during preharvest, harvest, postharvest processing, storage, preparation, and consumption of berries is presented.

Purpose: The purpose of this QMRA was to simulate the prevalence and concentration of Norovirus on frozen berries from preharvest through distribution, preparation, and consumption. The output of the model is predicted number of illnesses. The model simulated the largest known outbreak arising from Norovirus-contaminated berries. The outbreak occurred in 2012, in Germany, and was linked to frozen strawberries sourced from China.

Methods: The model was built in Excel using the Monte Carlo modeling software @Risk add-in. The QMRA was composed of five modules: in field, processing and packaging, storage, preparation, and consumption. Data from the scientific literature regarding Norovirus behavior in fresh and frozen fruit were used to develop the model.

Results: The literature data indicated transfer of Norovirus from hands to berries can be as great as 60±43%, if the berry is wet, and as low as 0.10±0.04%, when the berry is dry. Postharvest washing of berries with chlorinated water (1.7±0.4 mean log reduction) was significantly more effective than washing with warm (0.8±0.2 mean log reduction) or cold water (0.6±0.3 mean log reduction). Freezing and frozen storage results in a log reduction from 0.2 to 1.1 depending on freezing conditions and frozen storage time.

Significance: The model was successfully able to simulate the German frozen strawberry outbreak. Scenario analysis showed that heating the frozen berries prior to consumption was the most effective means to prevent illness.