Controlling Listeria in Fresh Produce: Views from a California Native

Posted by Monee Dulay on Jan 20, 2015 10:23:00 AM

Living in California, I am blessed by the abundance of fresh produce grown all around me. The varying climates and microclimates of California enable a diverse offering of fruits vegetables and nuts, from avocados and citrus in the South, to leafy greens and celery in the Salinas Valley, to almonds and pistachios in the San Joaquin Valley. My ideal location in San Diego enables me to network, engage, and understand both the common and varying needs of the industry as a Technical Sales Specialist with Roka Bioscience. In my discussions with local producers, the impact of the upcoming FSMA regulations and Listeria monocytogenes control procedures have been a chief topic across the board. In my research to support customers with industry information, I found this great resource by United Fresh Produce Association, Guidance on Environmental Monitoring and Control of Listeria for the Fresh Produce Industry.

The document discusses various aspects to control Listeria specifically in Fresh Produce operations including minimizing contamination in the field, designing hazards out of the facility, designing an environmental monitoring plan, and what to do if Listeria is ever detected. Here are a few points that I would like to highlight:

  • A validated process or preventative control will always be more reliable to ensure finished product safety than solely testing of the product itself.

  • An effective cleaning and sanitation program is the ongoing line of defense against Listeria becoming entrenched in a facility.

  • Use of ATP swabs used after the cleaning steps and before sanitizing can provide immediate feedback on the success of removing all organic material from the tested surfaces, but does not provide information about microorganisms.

  • The key to a successful environmental sampling program is an aggressive approach to finding and eliminating Listeria from the environment.

  • A random positive finding should be viewed as a “success” and an indication that your testing program has been effective.

  • It is recommended that testing be performed for Listeria spp as it is a more conservative detection and generally does not take as long as L. monocytogenes detection. The operation is expected to take corrective action for all Listeria spp detections as though they were L. monocytogenes.

  • Testing should only be performed on samples that are meaningful and would provide data that could be used for trending.

  • It is not recommended to using an in-house laboratory for testing L. monocytogenes or Listeria spp as the enrichment of samples could be a potential point of cross contamination in the plant. Instead, choose an external laboratory that is reliable (ISO 17025 accredited, follows Good Laboratory Practices, and/or participates in proficiency testing that includes Listeria testing).

  • Testing procedures should be sensitive. The operation should ensure that the testing laboratory is using validated detection methods and that they have sufficient internal controls to avoid “false negatives.”

The most important take away from the document is this: “The objective of an environmental monitoring program is not to prove the organism is absent, rather it is to detect the organism before it becomes a food safety risk.”  This is all pertinent and valuable information for the produce industry to reference, especially with the challenges of a short shelf-life of their product and the lack of a “kill step” as other segments have.  

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Topics: Produce Pathogen Detection, Listeria monocytogenes, Food Safety Technology, Training and Applications Support, Produce