Challenges and Innovations for On-Farm Bacterial Testing

By Amanda Kinchla, M.Sc., and Sam Nugen, Ph.D.

Each year, an estimated 47.8 million people in the U.S. will become ill from eating contaminated foods.[1] A study by the U.S. Centers for Disease Control and Prevention has recently concluded that leafy greens are responsible for almost half of these foodborne illnesses.[2] Foodborne outbreaks associated with produce have increased significantly, from 0.7 percent in the 1970s to 13 percent between 1990 and 2005.[3] From 1990 to 2005, there have been 713 recorded produce-related outbreaks and approximately 34,000 cases of illness associated with produce contamination.[3]

While demand has been growing for the consumption of fresh produce for better health and nutrition, at present, a pragmatic nonthermal process to reduce pathogenic risk in produce has not been put into practice. Food safety has continued to grow in importance, and the climate is changing to demand that stronger food safety programs are instituted throughout the food chain from farm to fork. Under the newly established Food Safety Modernization Act (FSMA), the U.S. Food and Drug Administration (FDA) will now have regulations for produce.[4] These regulations emphasize employee training, health and hygiene, agricultural water, biological soil amendments of animal origin, domesticated and wild animals, equipment, tools and buildings.[5]

Farmers will soon be responsible for validating the food safety of their on-farm water and soil. Part of the proposed ruling is to have agricultural water tested routinely to ensure that the water source is safe for its intended on-farm use. If the tested water fails the declared compliance, certain actions must be taken to make it safe (proposed sections 112.44 and 112.45). While these activities are intended to support the reduction of foodborne pathogens within produce, they will have a significant impact on many farmers’ methods of growing produce.

Current microbiological methods traditionally take between 24 and 72 hours to complete, plus the time it takes to send the sample to the laboratory for testing. In the operational process of produce, harvested product is shipped to distribution centers or sent directly to stores within 1 to 3 days to ensure the best quality and maintain that quality for at least 7 to 10 days. Adding more time to account for microbiological testing could be detrimental to overall product quality. Besides the time it takes to conduct testing, there are significant costs associated as well. The general cost to outsource a 100-mL water sample for an Escherichia coli/coliform assay to a microbiological lab ranges from $15 to $28 per sample. Due to the complexity of the test, currently this is the only option available for farmers.

During one of the most recent Q&A calls for the Produce Safety Alliance in regard to the Produce Safety Rules, many farmers expressed great concern about the proposed rulings for agricultural water. Farmers are very worried about how they will manage product if their water sampling results return out of regulatory compliance. One farmer pointed out that if he pulls a water sample on Monday, he would likely not get the results until Friday. The proposed rules require that you treat the water to ensure that the source is deemed safe; however, they don’t provide guidance on how to manage the produce that has been exposed to the contaminated water between Monday and Thursday. Although it is prudent that all contributors be involved in food safety, this issue illustrates a need for better on-farm tools to meet the upcoming food safety expectations.

While the current laws exempt small farms from mandated food safety plans such as a Good Agricultural Practices (GAP) certification, the climate is changing. Many wholesale and chain grocery buyers, such as Hannaford and Price Chopper, are requiring that their buyers have a GAP certification to reduce their business liability. Therefore, exempt farms that are not compliant to GAP certification may be at a significant competitive disadvantage if they do not initiate a food safety plan.

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