Design of fish processing equipment: exploring cleaning brush performance and material properties to minimize biofilm deposits

Abstract The development of bacterial biofilms in fish processing plants may facilitate the growth of human pathogenic bacteria such as Listeria monocytogenes and may therefore compromise food safety. In the Norwegian aquaculture industry, the cleaning of fish processing plants is the final process step during fish manufacturing processes. This article explores the efficiency of brushes of different designs in combination with using different cleaning methods in cleaning three types of material. A total of seven different brush designs (including those with soft, medium, and hard bristles; bristles also varied in length and density) and operational movements (linear versus rotational), were tested. It is believed that in the future, robots may clean fish processing plants, and equipping such robots with cleaning tools may significantly contribute to increasing food safety. This research investigates this future technology by investigating how tools that may be added to a robotic cleaning system will perform. The objective of verifying the performance of cleaning tools used in fish factories is to determine how effective they are in terms of the cleaning and removal of biofilm and how they perform with regard to cross-contamination. Test items of stainless steel, aluminum alloy and high-density polyethylene were experimentally inoculated with Pseudomonas fluorescence and Staphylococcus aureus, which were allowed to develop biofilms. Cleaning efficiency was analyzed spectrophotometrically by swabbing the cleaned test items and measuring the optical density at 600 nm in the swab eluates after overnight incubation. Cleaned test items and uncleaned controls were also stained with SYBR Green and photographed under ultraviolet light to evaluate biofilm removal efficiency by image analysis. Cleaning trials demonstrated that a rotating brush (240 rpm) performed better than brushes using a linear movement for the removal of biofilms on all material types, and that equipping robots with such tools may significantly improve cleaning performance. It is also found, however, that rotating brushes may introduce the risk of cross contamination due to splashing of bacteria into the air. The research findings and the methodology used for verification in this paper will serve as the foundation for future research on hygienic design and cleaning performance in the global fish processing industry.