Sampling and testing fresh produce, whether pre-harvest, as a raw material/ingredient, or as a finished product, should only be done with a full understanding of the statistical and practical limitations of testing, clarity around what a sample is being tested for, the purpose of testing, and the response to unacceptable results.
The 2010 Microbiological testing of produce paper discusses pros and cons of testing in different situations. The 2020 “key questions” document is a guide food safety professionals can use as a reminder of the numerous factors that should be considered when developing a sampling and testing program to detect pathogens in finished product. This includes the “how-tos” of a testing program, as well as how to interpret, act upon, and communicate a positive finding. Further, consideration should be given to managing supplier and customer expectations, including situations in which they are also testing product.
Because pre-harvest testing has unique complexities, specific resources are available. In addition to clarifying some misconceptions, there are several resources related to outbreak information provided by FDA which was used to reverse engineer a pre-harvest sampling plan that, with assumptions, could have detected the high level of contamination that presumably caused the outbreak. Visual illustrations and the background calculations are provided to support the explanation of this thought experiment.
Field sampling: Truth and Consequences (Originally developed by United Fresh)
Reverse Engineered Pre-harvest Testing Thought Experiment (Originally developed by United Fresh)
Visual Representation of Reverse Engineered Thought Experiment (Originally developed by United Fresh)
Calculations Supporting Reverse Engineered Thought Experiment (Originally developed by United Fresh)
FDA and states have the authority to test produce, either for cause, or as part of published or unpublished sampling assignments. Available resources include guidance pertaining to handling a regulatory sampling request, as well as factors to consider related to holding produce while waiting for a test result (whether taken by a regulator, your company, or a customer).
Handling a Regulatory Sampling Request (Originally developed by United Fresh)
Holding Produce Pending a Test Result (Originally developed by United Fresh)