Center for Produce Safety held our 10th Annual Research Symposium in person in Austin, TX in June 2019. In this review of 2019 highlights, we describe the key takeaways, and then place them in context as to why these findings are important and how they might be implemented or used by to the produce industry (growers, packers, processors, distributors and retail/foodservice), the research community and regulators.
In July 2019, CPS, United Fresh, Western Growers and Produce Marketing Association partnered to conduct a related webinar highlighting this symposium’s Key Learnings, and to answer questions from the webinar audience. The recording of that webinar can be found on pma.com. Additionally, the latest information about specific research projects mentioned in this document is available via CPS’s website, including our extensive research database and other produce safety resources.
These learnings are meant to inform and provoke thought with an eye towards inspiring readers to examine their own produce safety programs and to use the research to make improvements. They are not meant as a directive on what must be done to produce safe food.
Executive Summary
Twenty fully completed research reports and fifteen preliminary interim reports were presented at the CPS Research Symposium in Austin, Texas in June 2019. The program for the 2019 Symposium listing the projects presented can be found at www.centerforproducesafety.org. A summary of the key research learnings follows:
- A recurrent theme throughout the 2019 CPS Symposium was to warn against “one size fits all” approaches to solving produce safety challenges.
- Although disinfection of irrigation water sourced from canals in the Yuma Valley can be an important part of a strategy to reduce contamination risks associated with furrow irrigation, it does not eliminate the risks and needs to be supplemented with close attention to controlling water flow into the fields, diligent pre-harvest inspection to identify areas that may have become flooded and aggressive cleaning and sanitation programs to prevent the harvest equipment from facilitating pathogen transfer from contaminated soil or harvested product to subsequently harvested commodities.
- Animal intrusion or the use of contaminated open sourced water to mix pesticides can result in pervasive product contamination and need to be managed carefully.
- Reliance on “one size fits all” die-off rate that can be used by growers to permit use of water sources that exceed permissible standards set out in the Produce Rule is questionable. Die-off is not a linear function and data developed using attenuated E. coli and Salmonella strains on baby spinach and romaine describe die-off rates that are highly variable based on locations, species, produce type and trial.
- Microbial control in produce wash systems is dependent on the equipment or system being employed, the product(s) being washed, and the antimicrobial(s) or disinfectants used. The buildup of organic compounds in the water measured as chemical oxygen demand or COD over time results in reduced availability of active antimicrobials that can make the system itself a source of contamination. Predictive models are being developed that can help operators more effectively manage wash water to ensure effective levels of antimicrobials are reliably achieved.
- New detection methods for Cyclospora have made it easier to find this pathogen in water sources. Although Cyclospora has been found in open water sources in Arizona, no illnesses have been tied to products from Arizona. Adherence to good agricultural practices like inspection of irrigation water sources to make sure they are not compromised by effluents from sewage treatment plants and monitoring the health of workers and providing facilities and enforcing strict handwashing practices remain important tools for controlling this risk.
- When discussing testing surface waters for the presence of human pathogens, the “one size does not fit all” theme was evident. It is important to account for environmental (run-off from adjacent land), water chemistry (seasonal changes, dissolved oxygen in the water) and weather factors (rain, temperature, solar radiation) and to understand that the relationship between indicator organisms like generic E. coli and pathogens are variable. The industry needs to evolve to data- and risk-based sampling protocols employing sufficient volumes to account for these variables to truly be able to identify and manage contamination risks associated with surface water use.
- Systems approaches to managing defined produce safety challenges are emerging. Examples include the development of biological fences designed to prevent tree frogs from breaching the fence by using materials that leverage the biological structure of the frog’s toe pad to prevent gripping on the fence, the use of raptors to control their natural prey, nuisance birds and rodents, in leafy greens fields and finally the use of layered vegetative buffer zones to control airborne pathogen dispersion from poultry houses and small dairies onto neighboring vegetable production. These systems approaches provide growers with alternatives to manage on-farm risks.
- Whole genome sequencing tools are permitting researchers to track Listeria monocytogenes as it moves through production and non-production environments. On a macro level, distribution maps are being developed that identify prevalence of Lm throughout the U.S. Research focusing on specific production regions in California illustrates the technology permits tracking the movement of specific Lm strains between fruit packing facilities by season. The lament of “Listeria is everywhere” is proving to be true, but the emergence of whole genome sequencing gives the industry a tool that can be used proactively to discern problematic resident contaminations that can lead to public health risk and common sporadic occurrences that pose a less significant public health problem. In the end, seek and destroy strategies centered on aggressive environmental monitoring programs and cleaning and sanitation programs remain our best tools to control Listeria threats.
- Studies on how pathogen-supporting biofilms are formed in relationship to materials commonly used in equipment construction in packing and processing facilities has created awareness and a caution to growers that brushes used in many types of fruit packing to move, wash or apply postharvest preservation treatments can be difficult to sanitize owing to the porous surface of brush filaments. In another iteration of the dangers of “one size fits all” approaches, relying on standard sanitation practices across different types of surface materials is proving to be inadvisable. Materials being passed over equipment, the design of the equipment and the materials used, and the selection of cleaning and sanitization chemicals employed are important variables to be considered when developing sanitation strategies. An interim project report indicated that rechargeable antimicrobial and anti-fouling chemistries can be incorporated into films or used to coat harvest containers like bins, totes, RPC’s and buckets to help prevent biofilm formation and ultimately enable more practical cleaning and sanitation of these items.
This is the Key Learnings Executive Summary only. See the PDF link for more extensive information.