Postharvest water includes any water that contacts fresh produce or food contact surfaces during or after harvest.
This includes water used for rinsing, washing, cooling, waxing, icing, or moving fruits and vegetables. Postharvest water use may be a necessary part of fruit and vegetable production, but it is also a potential source of contamination. Understanding the risks associated with postharvest water use, and how to minimize them, are important for produce safety.
The key things you need to do to ensure the safety of postharvest water are to:
- Start with clean water. Water must have no detectable generic E. coli in a 100 mL water sample (1).
- Treat with sanitizer, or in some other way maintain water quality during use (2).
- Change bulk/batch tank water when dirty (3).
- Make sure water is at an appropriate temperature to avoid infiltration (3).
- Clean and sanitize tanks/bins regularly (4), making sure to reduce or eliminate pooled water (5).
- Document postharvest activities when required (6, 7) or as best practice.
Start with clean water
Only use water that has been tested and confirmed to meet the standard of no detectable generic E. coli in a 100 mL water sample as produce wash water (1). Water quality testing can be done by the farm or by the municipality or other water supplier, but the water must be tested to know its initial quality (8). Contaminated water can contaminate produce, so starting with clean water is essential. Do not use untreated surface water for postharvest uses (1). If you use surface water, you must treat the water and regularly monitor to make sure the treatment is effective. If sanitizer is used as the treatment, it must be used according to instructions on the label (9).
Add an appropriately-labeled sanitizer to postharvest water
Postharvest water, even if it is clean at the start, can become contaminated by produce that contacts the water. It is critical to maintain water quality during produce washing or other handling (2, 3). One way to do this is to add a sanitizer, labeled for the use, to all batch/bulk water. Adding a sanitizer does not clean each individual piece of produce, but it helps to prevent cross-contamination from the water to produce by limiting the buildup of pathogens and other microorganisms in the water. This is particularly important when many pieces of produce are submerged in the same water, or water is recirculated, because the risk of cross-contamination is highest at this step.
Cross-contamination is less of a risk in single pass water, but it is recommended that a sanitizer still be added to the single pass water. If single pass water is used inside equipment, use of a sanitizer can also prevent the formation of biofilms and minimize the risk of pathogen growth in biofilms inside the equipment.
A number of chemical sanitizers and treatment devices are labeled for use in postharvest water, including chlorine, chlorine dioxide, peroxyacetic (peracetic) acid, hydrogen peroxide, ozone, and UV light. The choice of water treatment depends on the application, the type of product, and what is allowed by your customer or certifying group. Sanitizers are considered antimicrobial pesticides, and their use is regulated by the US Environmental Protection Agency. Just like other pesticide types, the label is the law. Make sure the sanitizer you choose is labeled for the intended use, and follow the use instructions.
Always consider worker and environmental safety when choosing sanitizers. Remember to follow label use instructions for proper personal protective equipment (PPE) when handling and mixing sanitizers. The concentration of active ingredient must be routinely monitored, along with other requirements of the label use instructions (like pH), to ensure that the treatment is effective and reduces risks (9). Seek out expert technical advice before investing in a sanitation system or if you have questions.
Change bulk/batch tank water when dirty
Anything added to the batch/bulk tank water can introduce contamination. Leaves, stems, dirt, and even harvest containers submerged in the water can contaminate the water and reduce the effectiveness of sanitizers. To reduce food safety risks, bulk/batch water must be changed or filtered to avoid buildup of organic matter and recirculated water must be changed on a schedule (3). One way to monitor water quality is by measuring turbidity. This can be done through the use of a turbidity meter or by developing other water clarity standards based on measurable observations. Establishing water quality standards for your postharvest water will guide decisions about when to change water. Resources are provided at the end of this summary to help you decide what is right for your farm.
Make sure water is at the appropriate temperature to avoid infiltration
Some vegetables and fruits, especially tomatoes, cantaloupes, mangoes, and apples, are susceptible to water infiltration when the pulp temperature of the fruit is warmer than the water into which it is submerged. If the produce is warmer than the water, a vacuum can form inside the produce as the produce cools, causing water to be taken up into the fruit. If that water is contaminated, the produce can be contaminated both inside and outside. To reduce the risk of infiltration, monitor and keep batch/bulk water at an appropriate temperature for the commodity (3). Guidance is not available for all commodities. One recommendation is to keep the water at the same temperature or warmer than the pulp temperature and avoid deep tanks (deeper submersion results in higher pressure on the produce, and higher-pressure results in a higher risk of water infiltration).
Clean and sanitize tanks/bins/washers on a schedule
Making sure tanks/bins/washers are clean will reduce the risks of contaminating produce. Even when daily cleaning and sanitizing is not practical, like for complicated equipment that requires disassembly, a cleaning schedule should be established to minimize pathogen and dirt build-up inside the equipment (4). Develop a policy and SOP that includes step-by-step instructions for cleaning and sanitizing, including what needs to be cleaned, how often it is to be cleaned, and the process for cleaning it. Your cleaning SOP should be specific and identify what items, parts, drains, hoses, and other equipment need to be cleaned. Remember to include instructions on how to eliminate or reduce standing water in the tanks/bins/washers because standing water provides pathogens, such as Listeria monocytogenes, an opportunity to establish and persist. After cleaning and sanitizing tanks/bins/washers, all drip trays should be drained and any pooled water in the equipment should be removed as best as possible.
PPE and other necessary equipment should be specified in the SOPs. Use of photographs, drawings, and color-coding schemes is encouraged to aid workers in understanding exactly what needs to be done. SOPs should also be written in the language of the workers who use them. More information about cleaning and sanitation practices is available in the Sanitation and Postharvest Handling Decision Tree.
Document all postharvest activities
Keep records of postharvest water management and sanitation activities. Document the amount of sanitizer used (if any), monitoring steps, how often water is changed in flumes/tanks, pulp and water temperatures, and any other activities that are part of postharvest water management (6, 7). All activities should be outlined in your written farm food safety plan. Detailed SOPs and log sheets should be developed to ensure activities are done properly and documented. Sample SOPs and log sheets are provided within this decision tree.
The information in the template food safety plan, SOPs, and recordkeeping logs are examples you can use. They are not intended to be used directly. Tailor each to fit your farm operation and practices. These documents are guidance for risk reduction and for educational use only. These documents are not regulatory and are not intended to be used as audit metrics. These documents are subject to change without notice based on the best available science.
- FSMA, Produce Safety Rule. 21 CFR § 112.44. 2015.
- FSMA, Produce Safety Rule. 21 CFR § 112.41. 2015.
- FSMA, Produce Safety Rule. 21 CFR § 112.48. 2015.
- FSMA, Produce Safety Rule. 21 CFR § 112.123. 2015.
- FSMA, Produce Safety Rule. 21 CFR § 112.126. 2015.
- FSMA, Produce Safety Rule. 21 CFR § 112.140. 2015.
- FSMA, Produce Safety Rule. 21 CFR § 112.50. 2015.
- FSMA, Produce Safety Rule. 21 CFR § 112.47. 2015.
- FSMA, Produce Safety Rule. 21 CFR § 112.43. 2015.
- FSMA, Produce Safety Rule. 21 CFR § 112.46. 2015.
- USDA. Auditor Manual, Produce GAPs Harmonized food Safety Audit Program: Policies and Procedures. Washington, DC: USDA; 2016. 241 pages.
- FSMA, Produce Safety Rule. 21 CFR § 112.133. 2015.
- FSMA, Produce Safety Rule. 21 CFR § 112.21. 2015.
- Suslow TV. Top FAQs about Produce Wash Water Management for Small Scale and Direct Market Farms. Presentation at Center for Produce Safety Annual Meeting 2012.
- Tocco P. Handling Turbidity in Postharvest Wash Water. Michigan State University Extension Fact Sheet AFSM043-01. 2016.
- California Leafy Green Products Handler Marketing Agreement (LGMA). Commodity Specific Food Safety Guidelines for the Production and Harvest of Lettuce and Leafy Greens. 2020.