The Center for Produce Safety (CPS) has published an executive summary of the 2022 CPS Symposium, which took place June 21–22 in La Jolla, California. The Symposium centered on produce safety research and industry challenges, and the executive summary includes key learnings from the Symposium that produce companies can practically apply to their operations. The summary is categorized into three sections: findings that merit immediate actions, results that reinforce current best practices, and concepts that warrant observation.

Urgent Findings

CPS highlighted several learnings from the Symposium that it believes may be critical to ensuring produce safety at an organization. For instance, it is imperative to always confirm presumptive positives using multiple genetic sequences when testing irrigated water samples for Cyclospora cayetanensis. Additionally, it was found that hollow fiber filters can improve the capture of Cyclospora oocysts in irrigation water samples, leading to more comprehensive research on the pathogen. 

Other critical learnings from the Symposium relate to biofilm and temperature control. One study discussed at the Symposium suggests that it is urgent for facilities to validate the efficacy of their cleaning and sanitization practices; microbial testing revealed some production lines that were washed and sanitized after production to have higher counts of Listeria monocytogenes the next morning than during the production shift. The data also showed that biofilms can form overnight on rough surfaces, such as brushes, sponges, and plastics. 

Finally, a new tool was revealed at the Symposium that can lead to better temperature control, addressing the fact that surface temperatures are not always indicative of core produce temperatures. Low-cost, infrared cameras that are integrated into a cell phone can provide reliable, non-contact, non-invasive, and real-time measurement of core and surface product temperatures, and can also identify “hot spots.” Improved temperature control is important to controlling spoilage and pathogen growth.

Reinforcing Best Practices

The Symposium also highlighted findings that can be used to fine-tune industry best practices. According to the executive summary, hazards analysis and risk assessment are, at present, the best available tools for managing Cyclospora. Specifically, the summary suggests “knowing your water sources,” as understanding potential human fecal contamination transfer routes to water sources used in produce agriculture can mitigate the risks of Cyclospora. 

Regarding L. monocytogenes, the summary notes that it is important to use properly titrated quat-based sanitizers at manufacturer-recommended label concentrations. Improper use of quat-based sanitizers can lead L. monocytogenes strains to develop genetic tolerance to the chemicals when subject to sub-lethal concentrations of sanitizer for certain periods of time. 

Lastly, the summary recognizes that the effective use of wash water disinfectants can help minimize the risks posed by human enteric viruses. Research presented at the Symposium demonstrates that a one-minute contact time with 5–20 parts per million (ppm) sodium hypochlorite or 2–3 ppm chlorine dioxide is sufficient to control enteric viruses. 

Concepts to Watch

The summary lists several emerging concepts that may improve efficiencies, reduce costs, and ensure food safety, such as:

• The use of LED blue light for inhibiting the growth of L. monocytogenes on surfaces that are difficult to clean and sanitize
• The use of Listex, a commercially available bacteriophage mixture, for reducing the presence of L. monocytogenes on products that are susceptible to supporting post-harvest pathogen growth
• ListRisk, an app that is in development for the identification of factors contributing to post-harvest L. monocytogenes growth on leafy greens
• Ultra-fine bubble technology, a mechanism that may make wash water sanitizers more effective in wash systems
• The use of cold plasma for disinfecting wash water.

CPS encourages industry to look inward at its produce safety programs to examine current strategies and ensure that they reflect the current science, as outlined in the Symposium executive summary. More detail on the research projects highlighted in the summary can be found at www.centerforproducesafety.org.