Produce safety is meant to reduce and prevent contamination of produce with harmful human pathogens, such as bacteria, viruses, and parasites. This is done by controlling known risks. Other factors to be aware of include mechanical and chemical contamination, but this guide will focus on human pathogens.
Hydroponic and aquaponic production are unique, from a produce safety perspective, because of the way water is used, the specific constructed production systems in use, and how people are involved in the systems. Aquaponic systems have added produce safety considerations related to the inclusion of fish.

Hydroponic systems use stored and/or circulating nutrient rich water in greater volumes than other forms of production which presents unique produce safety circumstances. This is sometimes referred to as “nutrient solution” since it is “production water” that has nutrients added to it. For the purposes of this document, these terms mean the same thing.

Nutrient Rich

• Water delivered to the plants is full of nutrients, since this is the source of food needed for plant growth and crop production. Since human pathogens depend on water and food to survive and reproduce, there is a chance that this water can be contaminated with them.

Abundance

• The very nature of hydroponic production means that water is central to plant growth. This is true of other production systems, of course, but in hydroponic systems the potential for contact between production water and the edible portion of the crop is greater.

Circulation

• In most hydroponic systems, the water is also circulated.  This means that contamination in one place can quickly spread to other places and, perhaps, through-out the entire system.

Hydroponic production depends on constructed systems which introduce unique food contact surfaces in the growing environment.

Food Contact Surfaces

• Because hydroponic production doesn’t involve soil, other growing media and structural surfaces such as rafts and troughs are used. The media and support surfaces can become “food contact surfaces” due to the way plants grow and how the surfaces are handled. This requires special attention to these surfaces relative to cleaning and sanitizing. The abundance of nutrient rich water and its circulation also leads to connectivity between different parts of the system. For example, any surface that the recirculated water contacts should be treated as a food contact surface if the water later has the potential to contact any harvested food, or other food contact surface. The water connects all these surfaces.

Movement

• Product movement is unique in hydroponic operations as well. Sometimes rafts and troughs are moved prior to harvest. Other times, the primary movement is at harvest time. Regardless of the timing, it is important to take care when moving parts of the production system to prevent water dripping and contacting food contact surfaces or the harvested portion of the crop. Common examples to consider are:
  • lift each raft for harvesting in such a way that it does not drip production water over produce, other rafts, or other food contact surfaces, and
  • lift rafts out of the water in a way that prevents edges or corners from dipping into the production water which can lead to contact between production water and produce or food contact surfaces.

Cleaning and Sanitizing

• Given the considerations above, it becomes clear that cleaning and sanitizing food contact and water contact surfaces is critical for control of human pathogens (and plant pathogens). Unfortunately, many of these surfaces are not well designed for cleaning and sanitizing. So, there is a need to carefully document appropriate standard operating procedures (SOPs), appropriate cleaning and sanitizing tools and supplies, and think about continuous improvement through the application of hygienic design principles.

Watch as this Quick-Cut Greens Harvester gets cleaned and sanitized:

Due to continuous and high levels of production, hydroponic production tends to involve more human contact during the plant growth period. Growing surfaces are moved, water is managed, and harvest involves movement of product and surfaces by people.

Procedures and Practices

• Hydroponic operations tend to involve significant human interaction during the period of plant growth and in other ways that can result in contamination. Moving germinated plants to production surfaces, moving production surfaces through the production system, managing water supply, water treatment, and harvest occurring in or near the production area all tend to lead to human interaction with the system. Even cleaning and sanitizing of water contact and food contact surfaces, when not done completely, can present risk. These activities should be carefully planned and described so that each person completes them without introducing the risk of contaminating the system with human pathogens.

Worker Health and Hygiene

• Not working when sick, hand washing before and after contact with produce, water, or food contact surfaces, and ensuring all workers are trained and aware of produce safety risks and best practices are all measures that can reduce contamination risk.

This guide is meant to provide an introductory overview of key produce safety considerations for hydroponic growers. The table below provides specific items to discuss with your team and to act on as you develop a produce safety culture and plan. More specific resources are available below.

In 2022, NECAFS received funding from the USDA NIFA Food Safety Outreach Program (FSOP) to continue working in the area of hydroponic and aquaponic produce safety. This project has five primary objectives:

• Advisory Group - Form a nation-wide hydroponic and aquaponic produce safety advisory group that informs project outputs at multiple steps.
• Needs Assessment - Determine produce safety educational needs and gaps specific to hydroponics and aquaponics.
• Educational Resource Development - Develop educational curricula, programs, and resources for diverse audiences with interests in hydroponic and aquaponic produce safety.
• Education Delivery and Evaluation - Deliver educational resources and programs to relevant audiences and evaluate outcomes and impact.
• Coordinate Future Research - Coordinate research efforts to address knowledge gaps.

This 3-year project has begun with the formation of Advisory and Collaborator groups to help direct and plan the work. An initial needs assessment is being conducted to further focus educational curricula and program development. This process will also inform a research roadmap to direct future research to address identified gaps in knowledge.

If you would like to receive updates on new educational resources and programming, please don't hesitate to reach out to Sean Fogarty at sean.z.fogarty@uvm.edu. We also welcome those interested in becoming more involved by contributing to the advisory group, making connections between the project and growers, or collaborating on specific project activities.