A careful examination of the potential hazards and the contamination risks they might represent to your agricultural water is a critical step to avoiding a foodborne illness incident associated with your company’s products. Certainly, USDA’s Good Agricultural Practices (GAPs) and FDA’s Produce Safety Rule provide a blueprint for the types of hazards you might look for in your production environment and offer insights into the preventive controls you might employ to manage any potential cross-contamination risks.
But, let’s look a bit further into agricultural water and share some thought on:
- How to define agriculture water
- Why agricultural water is so impactful
- Factors to consider for preharvest water
- Practices to improve postharvest water quality
Types of Agricultural Water
Preharvest water is used during the production of the crop right up until harvest. Preharvest water commonly includes water used for all types of irrigation, mixing agricultural chemicals like pesticides or fertilizers, frost protection, and dust control.
Postharvest water has always been a high priority for producers since it contacts the crop after harvest and closer to when the product is consumed. If the water was contaminated with human pathogens, the potential for large-scale cross-contamination onto the crop is significant and could negatively impact public health. Postharvest water uses includes hydro-cooling, cooling with ice directly, water used for transporting products from harvest gondolas or field bins, and wash water.
Why Agricultural Water Matters
When it comes to foodborne illness outbreaks and fresh vegetables, agricultural water is often one of the first avenues of investigation. Agricultural water, both preharvest and postharvest, generally contact the edible surface of the product and can transfer pathogens to these surfaces facilitating the consumption and in some cases cause illness. It has been postulated that some of the recent national advisories focused on romaine lettuce contaminated with E. coli O157: H7 was due to the use of contaminated irrigation water. Outbreaks associated with the use of contaminated water used for ag chemical mixing have also been reported.
So, what can be done to ensure postharvest water quality?
Each source of water used in preharvest applications is different physically, chemically or microbiologically. One well might be deep, another shallow. Another might be an open irrigation canal or a fast-moving river, an on-farm pond or lake. For this reason, it is important to perform a hazard analysis and a risk assessment on each field and the water source you intend to use. What is the area around your water source that might represent a cross-contamination hazard where pathogens could find their way into the water? Animal feeding operations, wild animal intrusion, leaking sewage systems, runoff from adjacent composting areas, human interaction with the water like swimming are all potential hazards to consider. You must then consider the risk for cross-contamination these observed hazards represent. Could wind, animals, humans, or water runoff from adjacent fields or landscapes carry pathogens from the hazard to the ag water source for the farm? If it could, then you must develop preventive controls to manage the risk and take steps to measure its effectiveness. In some instances, disinfectants are being used on open water sources on farms though this must be carefully implemented to make sure the disinfection is effective and continuously monitored.
It is also important to assess the method for delivering water and how it is used on the crop. An open water source subject to cross-contamination used in overhead irrigation where the water contacts the edible surface of the plants would be expected to pose a more significant risk than the same water delivered via drip irrigation directly to the subsoil. It is also important to make sure the delivery systems; pipes, valves, sprinkler heads, filters, pumps and the storage areas for these pieces of equipment are all in good condition and not compromised so that they are not contaminated or could introduce pathogens themselves. Recently owing to suspected contamination issues with irrigation water, some commodity groups are mandating inspection protocols for water delivery systems prior to use as a mitigation step.
The Challenges with Postharvest Water
Because postharvest water used in washing, cooling or transporting the crop contacts the surfaces and because these systems are in a continual flow, i.e. large volumes of crop move through these systems in between water changes, the chance for large-scale cross-contamination is significant. For example, if a field were harvested where only ten or twenty leaves of spinach were contaminated with Salmonella owing to bird droppings, as the leaves entered the wash water and the droppings containing the pathogen were rinsed into the water, the freed Salmonella cells in the water could contaminate thousands of uncontaminated leaves moving through the wash system over the next few hours. So, what was small contamination of only a few leaves becomes a much larger public health risk spread among a large volume of finished packages. That is why so much emphasis has been placed on postharvest water disinfection and management.
Some best practices to consider:
- Know your water source. Characterize the water used in your wash, transport or cooling operations. Is it municipal water and therefore drinking water quality or is it from an open water source that is likely to be contaminated periodically?
- Use properly managed water disinfectants. Choose a disinfectant that meets your systems requirements and monitor the concentration of the disinfectant continuously to avoid depletion and subsequent periods where the water might become a source of cross-contamination.
- Validate and verify the disinfection of your water. You cannot add disinfectant and assume it will control pathogens in the water. It is important to prove what you are doing to control pathogens in the water is effective and defines the operating conditions for success. This is called validation. Thereafter, you must verify you’re your validated system is operating within the parameters. This is called verification. Verification is generally accomplished by measuring the water chemistry, e.g. disinfectant level, pH chemical oxygen demand or other factors.
- Change the water. Over time, water that is in continuous use or in contact with large volumes of raw produce can change chemically and accumulate several organic compounds. These changes in chemistry often work against disinfectants, inactivating them; causing the system to fail to control microbial populations. Many operators choose to change the water periodically to prevent large organic loads from building up. The time it takes to change out water should be scheduled during the day as part of the operations of the plant.
- Keep your systems cleaned and sanitized. Clean and sanitize dump tanks, flumes, wash tanks, and hydro-coolers daily. It is important to have a master sanitation schedule and standard sanitation operating procedures (SSOPs) in place to ensure efficient and effective and verified sanitation.
- Perform regular inspection and maintenance of water systems. Equipment used to maintain your water quality like disinfectant injectors, filtration systems, and backflow devices should be well maintained to prevent contamination.
When developing a comprehensive, science and risk-based produce safety program, agricultural water uses must be a top priority. To find more information on ag water management and other aspects of produce safety programs, check out our Essentials of Produce Safety course. It’s your next step to better protecting your company against food safety incidents and building a brand customer’s trust. Zosi and the Produce Marketing Association (PMA) developed this course to help you explore all the facets that can impact the safety of your products.