Clean Water, Clean Produce: Agricultural Water Testing Under FSMA

According to the Food and Drug Administration (FDA) and the Centers for Disease Control (CDC), the United States saw 131 produce-related outbreaks of foodborne illness between 1996 and 2010. These incidents — linked to 20 different produce items — caused 14,350 illnesses, 1,382 hospitalizations, and 34 fatalities. According to the FDA, this represents a significant public health burden which could be prevented.¹

As a response to this data, the FDA produced the Food Safety Modernization Act (FSMA) of 2011. This legislation moved the FDA’s response to foodborne illness from reaction to prevention, thereby enhancing the US food safety program as a whole. Under FSMA’s Produce Safety rule, the FDA received a mandate to set minimum standards for those growing, harvesting, packing, and holding produce.¹

One particular area of concern regarding produce, is agricultural water quality. A recent application note describes specific requirements for testing agricultural water for the presence of E. coli in compliance with FSMA.² According to the author, the Produce Safety rule addresses two aspects of E. coli testing:

Any water that might transfer pathogenic microbes to produce must be free of generic E. coli. This includes water used during and after harvest and for washing hands and surfaces.
Any agricultural water applied directly to growing produce (except sprouts) must meet two standard metrics. The geometric mean (GM), or average amount of pathogen across samples, must not exceed 126 colony-forming units (CFU) of generic E. coli per 100 ml water. The statistical threshold (STV), or variability of pathogen levels in adverse conditions, must not exceed 410 CFU generic E. coli per 100 ml water.

Generally, agricultural water testing should be performed at least annually for untreated ground water and at least five times per year for untreated surface water.

The application note describes a membrane filtration procedure suitable for testing for E. coli in agricultural water. This method meets standards set by the Environmental Protection Agency (EPA) and satisfies FSMA requirements. Briefly, the researchers filtered sample water through a membrane, followed by rinsing twice with phosphate buffered saline. Then, they placed the membrane onto an mTEC (membrane thermotolerant E. coli) agar plate and incubated (2 ± 0.5 hours, 35 °C ± 0.5 ˚C) for organism recovery. Next, they sealed the plates in a sterile plain bag and subjected them to further incubation in a water bath (22 ± 2 hours, 44 ˚C ± 0.5 ˚C). This enabled direct counting of red or magenta (i.e. ‘typical’) colonies. The method recommends subsequent confirmation testing based on true E. coli characteristics: oxidase negative, citrate negative, indole positive, EC broth growth and gas production.

The FSMA regulations, including the Produce Safety rule, impact all produce growers and processors with specific impacts associating with region and climate considerations. For instance, the Western states (California, Oregon, Washington, and Idaho) must contend with drought, rendering it a particular challenge to predict water availability, sourcing, and cost.³

Other notable impacted bodies are producers who import into the US. According to the CDC, the US imports 50% of its fresh produce, and imported foods bore responsibility for 39 outbreaks of foodborne illness between 2005 and 2010, with over half occurring in the last two years of the dataset.⁴ Under FSMA’s Final Rule on Foreign Supplier Verification Programs (FSVP), importers are subject to specific obligations to identify hazards, determine risk, assign verification activities accordingly, perform verification activities for suppliers, and enact corrective actions when appropriate.

When it comes to agricultural water testing and produce safety, the FSMA mandate is clear. Concise, robust testing methods like the one in the application note discussed here can assist domestic producers and importers in meeting regulation standards. For further reading on this and related topics, see the article The Food Safety Modernization Act: Global Impacts for Microbiological Food Safety and this food microbiology testing compendium.

References

1 US Department of Health and Human Services Food and Drug Administration “Food Safety Modernization Act: Produce Safety Standards.” Page Last Updated: 08/24/2016

2 Dougherty, A. (2016) ‘FDA Food Safety Modernization Act (FSMA) introduces generic E. coli test requirements for agricultural water that may come into contact with produce or food surfaces.’ Application Note, LT2308A.

3 Ostroff, S. “Visit to West Coast Farmers and Processors Finds Shared Commitment to Food Safety.” FDA Voice, 10 November 2016.

4 Betts, R. (2016) ‘The Food Safety Modernization Act — Global Impacts for Microbiological Food Safety.’ Culture 36 (1).