A Food Safety Progress Report
September 1, 2007 Although I uniformly use this column as an opportunity to share current technical information and applied knowledge, I felt it appropriate to diverge one time into sharing a personal opinion on the progress made to provide safe produce to consumers.
It has been one year since a sequence of outbreaks associated with E. coli on leafy greens, in each case minimally processed, gained international attention and rocked the confidence of suppliers, buying customers, and consumers in the fresh produce supply chain.
During the same period in 2006, additional outbreaks of Salmonella on tomatoes were being investigated but went largely unnoticed by the media. Sales have not fully recovered and, although substantial progress has been made to further advance the design and implementation of food safety programs in this sector, it would be unrealistic to overstate current gains in public protection from future outbreaks.
Science-Based Opinion
As we have approached the 2006 anniversary of these tragic and sobering events, I have been asked repeatedly whether consumers are better protected now, in consuming packaged salads, than one year ago. I am not qualified nor presume to pass myself off as a pundit with access to full inside information. However, as an applied researcher and Extension specialist very much tied to the issues, I have felt it my responsibility to try to offer objective, science-based opinions.
While conveying a perspective of continuing low risk, based on historical levels of consumption, and a sincere belief that new programs implemented over that past several months have gone further than before to broaden the foundation and practical specifics of Good Agricultural Practices (GAP) across the produce industry, I also share a deep concern that the industry, regulators, and researchers alike remain substantially ignorant of the “real-world” specifics of contamination sources, events, and the fate of human pathogens on fresh produce. One measure of this certainty is that the significantly expanded effort and investment in microbiological testing of preharvest inputs, harvested product, and finished product within the leafy green industry has demonstrated that detectable incoming product contamination, though very low (reportedly less than 1%), is being caught.
Though preliminary, the expanded surveillance has a good chance of identifying problematic areas and confirming or discrediting suspicions of presumed sources of contamination. However, from an Extension research perspective, the concern remains that what is detectable with current techniques may only be a portion of what
is present.
What is detectable is the result of many interacting factors but most significantly the quality and scope of the sampling strategy. For example, based on rigorous statistical models, a 1% level of contamination in a lot would require 300 samples to achieve a confidence level of 95% that positive detection will be achieved. This is based on uniform distribution of contaminants, which we know from sampling commercial fields for indicators to be unlikely in the majority of environmental and production situations. I am not aware of any program that does or could afford to take this costly approach.
So at this early stage, what is being learned from the combination of presumptive and confirmed detections that the industry is publicly discussing?
• Key pathogens of concern, such as E. coli O157:H7 and Salmonella, while detected in very low frequencies, may be part of the production environment.
• Lots, with arguably the greater possibility of resulting in a multi-state outbreak, are being prevented from entering commerce.
• Tracing the source of detected contamination remains a very challenging and non-successful effort, at this time.
• The developing standards and limits need to be responsive to the building database of field-acquired information.
• The industry and public will greatly benefit by consolidating and sharing key learnings in a timely manner.
Suslow is Extension research specialist Postharvest Quality and Safety, University of California-Davis; [email protected].
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