The 2022 Center for Produce Safety Symposium, held June 21-22 in San Diego, featured produce safety research presentations and industry discussions on a wide range of critically important produce safety challenges. 

This executive summary can be used to look inward at your own produce safety programs to examine current strategies and ensure they reflect the current science. Executives can also look outward and engage customers, trade groups and regulators to set the framework for trust-building discussions and data-sharing opportunities to advance mutual produce safety objectives and enhance consumer confidence in fresh produce. 

This summary is organized into three areas to guide executives in the action levels they need to take: (1) results that merit immediate action from your produce safety team, (2) results that reinforce current best practices and represent opportunities for renewed training or finetuning and lastly, (3) findings you should be aware of and monitor as further research enables practicable operational value.

New learnings from the 2022 Symposium critical to your company’s journey to more effective produce safety are briefly described below: 

• When it comes to Cyclospora testing, always confirm presumptive positives. Before testing irrigation water samples for Cyclospora, it is important to understand the current scientific literature on environmental Cyclospora and the decisions that can be made given the limitations of this testing. Currently, no single DNA-based testing method is capable of discerning C. cayetanensis from other genetically related parasites commonly found in growing environments (e.g., Eimeria) [Mattioli 2019, Ortega 2019, and Kniel 2019]. It is imperative to confirm presumptive PCR-positive tests using multiple C. cayetanensis-specific mitochondrial or nuclear genetic sequences. 

• Hollow fiber filters improve capture of Cyclospora oocysts in irrigation water samples. Detecting Cyclospora offers several technical challenges; among them collecting enough oocysts to permit DNA-extraction needed for PCR testing. Hollow fiber filters permit large volumes of water to be passed through the system to filter out oocysts in sufficient numbers to support DNA extraction [Ortega 2019]. Increased availability of oocysts and DNA permits more extensive Cyclospora research leading to more sensitive and selective detection tools. 

• Think your equipment is clean and sanitized? Biofilm formation on equipment represents an important challenge in controlling Listeria risks. Rough, porous surfaces on harvesting, packing or processing equipment offer Listeria monocytogenes (Lm) and other microorganisms niches to reside in and deposit biofilms that permit them to survive inadequate cleaning and sanitation and even grow in production environments. A study of Lm and biofilm control conducted in seven peach packinghouses revealed that in some of the facilities, lines washed and sanitized right after production ended and left till start-up the next morning surprisingly had higher aerobic plate counts than what was found during the production shift [Dawson 2019]. 

• A new tool to permit more effective temperature control. Think you are cooling your products properly? You might want to think again as surface temperatures are not always indicative of core produce temperatures. Low cost ($450-700) infrared cameras integrated into a cell phone permit reliable, non-contact, non-invasive, real-time measurement of core and surface product temperatures [Mis Solval 2020] to help control spoilage and pathogen growth. Infrared cameras can also enable identification of “hot spots” and permit better temperature control in distribution facilities. 

The Symposium also featured projects that built upon our knowledge base to provide opportunities to fine-tune best practices: 

• Hazard analysis and risk assessment are currently your best tools for managing Cyclospora. Surveys of open water sources in California and Florida yielded about 10- percent presumptive Cyclospora positives. Follow on confirmation testing indicated these samples were largely genetically related species of Eimeria and Isospora [Ortega 2019]. Similar water sampling in Georgia yielded forty-seven presumptive Cyclospora positives yet confirmation testing showed these to be false positives [Mattioli 2019]. 

• Pay attention to your use of quat-based sanitizers. FDA has suggested operators rotate sanitizers to prevent pathogens from becoming tolerant to common quat-based sanitizers. An earlier CPS project suggested the development of genetically heritable tolerance is unlikely [Wiedmann 2019]. A new research project [Deng 2019] examined 25,000 strains of Lm isolated in U.S. food processing operations for the bcrABC gene which confers increased tolerance to quat-based sanitizers (benzalkonium chloride). 94.6-percent of the isolates were found to harbor the bcrABC gene. 

• Effective use of wash water disinfectants can help you control the risks represented by illness-causing human enteric viruses. The MS2 bacteriophage shares characteristics of the human enteric hepatitis A virus and can be used as a surrogate to study the efficacy of preventive controls to mitigate cross contamination by enteric viruses in produce wash water systems [Sánchez 2019]. Research demonstrates that commonly employed wash water practices, a one-minute contact time with 5-20 ppm sodium hypochlorite or 2-3 ppm chlorine dioxide, is sufficient to control enteric viruses. 

The 2022 Symposium featured new concepts addressing an array of current industry challenges: 

• Help may be on the way. Packinghouses and processing operations often rely on electronic equipment (e.g., optical sorters, scales, metal detectors and electric motors) that are sensitive to cleaning and sanitation chemicals and water. LED antimicrobial blue light (aBL), wavelength 405 nm, can be used to achieve a 100 to 10,000-fold reduction of Lm on otherwise difficult to clean and sanitize surfaces [Diez-Gonzalez 2020]. 

• Using viruses to kill bacteria: encouraging results for a natural approach to managing Lm. Bacteriophages are like viruses that infect and kill bacterial cells. A commercially available cocktail of bacteriophages, ListexTM, consistently achieved a 100-fold reduction of Lm in produce under laboratory conditions. It was also demonstrated that applications of sufficient doses of phages (106 to 107 ) through water sprays were achievable in commercial operations [Allende 2019]. 

• Lm growth on produce - you just knew there would be an app someday. ListRisk is an app being developed for leafy greens that will help operators identify factors contributing to postharvest growth of Lm [Allende 2019]. The model is being constructed with over 600 data points and uses temperature, pH, water activity and other factors to predict growth potential for Lm on leafy greens. 

• Ultrafine bubble technology may hold the key for more effective wash water sanitation. Ultra-fine bubble technology may be a mechanism for delivering wash water sanitizers more effectively in wash systems. Research using ozone in combination with ultrafine bubble technology demonstrated promise for industry use [Upadhyay 2020]. Ultrafine ozone-containing bubbles reduced Lm levels by 10 to 250-fold on the surface of lettuce, apples, and celery with exposure times of one to two minutes at 4°C without damaging product quality. 

• Cold plasma to disinfect wash water? Remember the four states of matter – solid, liquid, gas and plasma? Bet you missed the plasma state, didn’t you? Think of solid ice. When heated, the solid turns to a liquid (water). Applying more heat, water turns into steam, a gas. If even more heat is applied to the gas, a plasma forms which is a highly reactive state consisting of high temperature electrons, ultraviolet photons, cooler charged and neutral atoms and other reactive chemicals that have antimicrobial properties. 

The Woodland, Calif.-based Center for Produce Safety is focused on providing the produce industry with information on enhancing the safety of fresh fruits and vegetables.