Scientific findings can provide practical solutions to solve many of the food safety challenges the produce sector is facing. Last month, the Center for Produce Safety (CPS) hosted their seventh annual Research Symposium in Seattle. This event covered subjects such as: 1) Listeria, 2) surrogates and indicators, 3) irrigation water management, 4) process validation and verification; and, 5) animal intrusion and on-farm pathogen detection. Many of the key research findings and potential food safety solutions are very relevant to ag operation.
What is coming down the pike?
Listeria monocytogenes (L. mono) outbreak and caramel apples
The review of the L. mono outbreak in caramel apples was probably one of the best discussions of the symposium. Ian Williams with the Centers for Disease Control and Prevention (CDC) explained how intergovernmental collaboration and the use of PulseNet (a network of public health and food regulatory agency laboratories in the United States) played a key role in identifying the source of the L. mono outbreak last year. Once “caramel apples” were identified as the culprit, the California Department of Public Health (CDPH) conducted an outbreak investigation. As a result, the operation implicated in this event was closed until corrective actions were implemented and verified.
Even though this recall was only linked to one operation in Bakersfield, Calif., it impacted several states and even international trade. Misinformation shared via social media resulted in many countries ceasing imports of apples from the United States. The situation was further affected by a lack of communication and coordinated target messaging between the FDA and the USDA Foreign Service. All told, the commercial ramifications for the U.S. apple export market totaled a loss of $15 million, reported Mark Powers with the Northwest Horticultural Council. These unfortunate circumstances demonstrated the importance of intergovernmental communication and targeted messaging.
It was remarkable to have the apple industry, government and academia talking about this outbreak, and sharing mistakes and lessons learned. It was also stunning to hear from an industry that had never before experienced such an outbreak and the broad impacts beyond the implicated company. While GAPs training has been widely accepted among fresh apple producers, the focus has now shifted to Listeria control, training, cleaning and sanitation in packinghouses as well as the use of guidance documents for tree fruit operations. In addition, industry has been working with academia to determine preventive measures and potential food safety risks. The University of Wisconsin, UC Davis, Cornell University and the Washington Tree Fruit Research Commission shared the results of research conducted in apple operations to understand how the outbreak occurred, how a facility can be vulnerable to contamination, and the need to implement practices that address situations where Listeria is widely distributed in an operation.
Surrogates and Indicators (organisms used to study the fate of pathogens)
The search for surrogates continues with the goal of improving pathogen testing in commercial agricultural settings without introducing them into the environment. Dr. Kelly Bright with the University of Arizona shared preliminary findings about the potential of viruses to be a new indicator of fecal contamination in irrigation waters. Dr. Sam Nugen with the University of Massachusetts shared ongoing work toward the development of a rapid bacterial testing device using bacteriophages (viruses that attack specific bacteria) in the form of a dipstick rapid test that can be used for on-farm detection of Salmonella ssp.
In addition to rapid detection, the use of tools such as Whole Genome Sequencing (WGS) is facilitating pathogen detections and expediting outbreak investigations. Dr. Martin Wiedmann from Cornell University mentioned that it is highly likely to see 10, 20 or 30 times the outbreaks in a couple of years. While some see WGS as a threat, this technology provides a valuable diagnostic tool and may have useful applications at the farm/facility level.
Irrigation Water Management
Research confirms that canal systems are dynamic. Dr. Marc Verhougstraete with the University of Arizona has made available guidelines to monitor irrigation water from canals, which consider best time for sampling, number of samples and specific sampling locations. Research on better predictive tools that provide greater flexibility in sampling is also underway to address: 1) the need for rapid, predictive and comparatively cost-neutral indicators of the potential for chronic or acute fecal contamination in irrigation water, and 2) the need to establish a microbial water quality profile under FDA’s Produce Safety Rule. Dr. Trevor Suslow with UC Davis stated that while generic E.coli remains a questionable indicator of fecal loading in irrigation sources, it is still useful. He also suggested that total bacteroidales (environmental bacteria used as indicator of water contamination) threshold values may be a better predictive tool providing more flexibility for sample collection. Dr. John Buchanan from the University of Tennessee shared the results of research on multiple disinfection methods including UV light and found that specific concentrations can disinfect surface water with suspended and dissolved solids.
Process Validation and Verification
Validation and verification are often incorrectly used interchangeably, when validation is actually one way to verify practices and processes. Validation evaluates information to determine whether a preventive control is in fact controlling an identified hazard. Validation of wash water programs is key, without a validated program in place; operations may be at a higher food safety risk. On this topic, Dr. Mary Anne Amalaradjou with the University of Connecticut shared that wash water has been implicated in all seven mango-implicated Listeria outbreaks reported in the United States. She made a point about the value of commodity-specific validation and verification studies, which is in line with ongoing research presented by Dr. Bradley Marks with Michigan State University who noted that the validation process for the pasteurization methods used for almonds or other nuts do not work for pistachios. Finally, another key point was made by researches of the University of Connecticut about the value of automated sanitizer feeding systems with continuous monitoring for maintaining wash water quality.
Dr. Mary Lou Tortello with the FDA presented probably the most complete work on validation of wash water resulting from a working group established a few years ago. This paper, soon to be published in the peer-reviewed Journal of Food Protection, is specific to fresh-cut leafy vegetables, but provides a template for other commodities. The lack of published studies, technological advances, and understanding about what affects antimicrobial effectiveness were identified as factors that delayed the completion of this study for nearly three years. Nevertheless, members of the working group believe the 3-year effort paid off by providing this paper as an important tool for assisting fresh-cut facilities to comply with validation requirements in the Preventive Controls Rule.
Animal Intrusion and on-farm pathogen detection
Some interesting projects investigating animal-related contamination risk were discussed. The use of video monitoring to manage/control animal intrusion is currently being tested. While it may not be cost-effective, it is providing some interesting information about animal behavior in production areas and has the potential to be used as a monitoring tool to gather site-specific information. Dr. Martin Wiedmann explained a geospatial model to develop predictive maps for identifying environmental reservoirs of L. mono on produce farms. Though this model was developed for a particular region on the East Coast, it could be used to develop state- or region-specific models for predicting risk areas and conducting hazard assessments. A user-friendly tool is currently under development.
Closing remarks by Drew MacDonald, vice president of quality and food safety at Church Brothers, LLC, and the newly appointed chair of CPS’ Technical Committee, highlighted that applied research is key to improving produce safety and that perfection should not be the enemy of good research. The best research, he said, comes from collaboration and practical work.
Western Growers was a proud Platinum Sponsor of the CPS Research Symposium 2016.
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