EFSA experts have examined the quality of water used during operations in the fresh and frozen produce sector.

The European Food Safety Authority (EFSA) asked the Panel on Biological Hazards (BIOHAZ) for a scientific opinion on the microbiological hazards associated with water use in the post-harvest handling and processing fresh and frozen fruits, vegetables, and herbs.

Water use during harvesting and processing is a significant risk factor for contamination of such products. Relevant microbial hazards include Listeria monocytogenes, Salmonella, E. coli, and viruses such as norovirus.

Large volumes of water are used for washing, rinsing, fluming, chilling, cooling, general cleaning, sanitation, and disinfection. For example, large amounts of water are needed to produce bagged salads. Most post-harvest processors favor using the same water during many hours of operation to save water and energy because access to potable water can be limited or expensive.

based on current practices, potable water is used to fill the equipment and tanks during the first hour in the morning and is not replaced for several hours or even days in some cases, during which time large volumes of fruit, vegetables, and herbs may be processed, according to the report.

Water treatment
Process water contamination is affected by several factors, including the type of produce being processed, duration of the operation, and transfer of microorganisms from the product to the water and vice versa.

To avoid cross-contamination of the product due to the use of contaminated water, water disinfection treatments are needed to eliminate or reduce microorganisms to an acceptable level, but they should not harm the quality and safety of produce.

The efficacy of disinfection treatments depends on the specific processing operation conditions, including the initial water quality and the type of treatment.

Chlorine‐based disinfectants and peroxyacetic acid are common water disinfection treatments. Validation, operational monitoring, and verification to demonstrate performance are needed. Hygienic practices include maintenance of infrastructure, training staff, and cooling of post‐harvest process water.

Water management
Expert efforts included a literature review, outbreak monitoring data, and an industry survey.

Water control based solely on a basic prerequisite program (PRP) is no longer feasible, and a HACCP-based approach is required for water management. Good manufacturing practices (GMP) and good hygienic practices (GHP) related to a water management plan and implementation of a water management system are critical.

based on replies from the industry survey, three good practices are not yet well implemented: replacing infrastructure to avoid biofilm formation, seeking biofilm formation in the water management system, and water cooling. Responses showed that monitoring the quality of process water was absent or weak.

In some listeriosis outbreaks, investigations found that contamination occurred at the processing plant; however, bacteria may also enter the factory from primary production. Despite outbreak investigations, the route of contamination was rarely /confirm/ied. 

Emerging agricultural practices such as hydroponics, vertical farming, and urban agriculture may introduce pathogens into the food chain, although the extent of this is expected to be lower than conventional farming, according to the report.

The BIOHAZ Panel recommended that more information should be included in outbreak investigation reports and clear guidelines should be available for companies to clarify the requirements on how water disinfection treatments can be used in maintaining the microbiological quality of water used in the post-harvest handling and processing of fruit, vegetables, and herbs.