Making a SPLASH with fresh-cut lettuce safety

A 12-month project called SPLASH achieved positive results after testing an innovative washing process for fresh-cut lettuce based on non-thermal plasma technology to increase product safety, quality and sustainability.

In this process, plasma-treated wash water (PTW) is used in a newly developed washing machine adapted to serve this precise purpose. The process for the hygienisation of the lettuce is designed to help to reduce the risk of packaged cut salads being contaminated with microorganisms.

Funded by the German Federal Ministry of Food and Agriculture (BMEL), the project partners included Leibniz Institute for Agricultural Engineering and Bioeconomy (ATB Potsdam), Gartenfrisch Jung, Leibniz Institute for Plasma Research and Technology (INP Greifswald) and KRONEN.

To prove the efficacy of the process in an industrial setting, tests using PTW to process baby leaf lettuce and other types of lettuce in the HEWA washing machine developed by KRONEN were carried out over several months at the facility of the fresh produce manufacturer Gartenfrisch Jung. These tests examined the disinfection efficiency in the wash water and on the treated products, resource savings compared to other disinfection methods and the optimisation of the products’ suitability for storage and transport.

The development of the HEWA washing machine focused on achieving a hygienic design to ensure that the machine has no horizontal surfaces, thus allowing the water to optimally discharge. The washing machine can additionally be fully dismantled for easy and thorough cleaning and is therefore optimised in terms of hygiene and a reduced cleaning time.

The use of the HEWA washing machine with plasma-treated wash water (PTW) revealed promising results, with the laboratory examination of the treated lettuce and the water samples providing evidence of a positive antimicrobial effect compared to the washing process using normal tap water. No negative effects of the treatment on the product were detected. These results show that the project achieved its objective of developing a resource-conserving washing process using non-thermal plasma technology for disinfecting cut lettuce as gently as possible. The hygienisation of the lettuce is designed to increase consumer safety by avoiding premature spoilage.

Following the completion of the project, the partners will continue to work together to publish the results and make the developed solution ready for the market in terms of industrial use, as well as to clarify issues concerning the classification of PTW as a production resource and its declaration of conformity.