EFSA analyzes water quality used in produce processing

European experts have looked into the microbiological quality of water used in processing fresh and frozen fruit, vegetables and herbs.

The quality of water and its industrial use is a concern because poor quality can introduce harmful microorganisms into food products. There is also the issue of climate change and the expected reduction in water availability. 

Experts analyzed the microbial and physico-chemical quality of water used during post-harvest to process fruit, vegetables and herbs in industrial settings. They also prepared a set of process water management plans and an online tool to help industry improve such management systems. A water management strategy should have validation, operational monitoring and verification. 

Scientists followed the concept of “fit-for-purpose water,” developed by the UN Food and Agriculture Organization (FAO) and World Health Organization (WHO). This approach calls for different aspects to be considered, such as assessment of the water source and potential related hazards, disinfection options, and end use of the food product.   

Recommendations by the European Food Safety Authority (EFSA) are shared in three scientific opinions on fresh-whole fruit, vegetables and herbs; on fresh-cut products, and on frozen products.  

EFSA also developed an online tool to help predict the transfer and accumulation of bacteria in process water in industrial scenarios. It works with preset or customized data, using a mathematical model to simulate scenarios and predict the impact of different strategies for water disinfection and replenishment. The app considers parameters such as volume and replenishment of water, chlorine disinfectant concentration, total volume of product being washed, and total bacteria counts.

Maintaining water quality
As part of the work, scientists analyzed practices followed by European food companies to maintain water quality used in post‐harvest handling and processing operations.

Contamination of process water during post‐harvest handling and processing operations is affected by several factors including the type of fruits, vegetables and herbs being processed, duration of the operation, and transfer of microorganisms from the product to the water and vice versa.

Data were obtained from 61 businesses. The impact of no water treatment was evaluated in 17 scenarios, while in 44, the challenges of maintaining the microbiological quality with water disinfection agents were examined, including chlorine, peroxyacetic acid, and hydrogen peroxide. Hygienic practices include technical maintenance of infrastructure, training of staff, and cooling of post‐harvest process water. 

Findings highlighted that when no water disinfection treatment was used Listeria monocytogenes was detected in some scenarios of the fresh‐whole and frozen fruit, vegetable and herb sectors as well as Salmonella, pathogenic E. coli and norovirus in fresh‐cut and frozen produce. Inadequate monitoring systems resulted in either excessively high or insufficient disinfectant concentrations in the water, which, when too low, failed to sufficiently reduce microbial load.

A literature review revealed a tendency to focus on leafy greens, use chlorine‐based disinfectants, and chemical oxygen demand (COD) as the primary physico‐chemical parameter, with total dissolved solids (TDS) and turbidity considered to a lesser extent, as indicators of water quality. 

Industry data indicated that the fresh‐whole fruit, vegetable and herb sector includes variable operational cycles lasting between 8 and 900 hours, large product volumes (e.g. more than 6,000 tons) and process water at 2.8 degrees C to 25 degrees C (37 to 77 degrees F).

The fresh‐cut fruit, vegetable and herb sector has process water at cooled temperature, operational cycles between 1 and 15 hours, and product volumes between 700 and 3,000-kilograms. The related frozen sector has operational cycles between 8 and 120 hours, variable product volumes and no control of the temperature of process water. 

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