A novel set-up and a CFD approach to study the biofilm dynamics as a function of local flow conditions encountered in fresh-cut food processing equipments

The hydrodynamic conditions as well as design and surface properties within fresh-cut food processing equipment create a complex environment for biofilms. A new experimental approach was thus proposed to identify those physical parameters impacting biofilm development in such conditions. A set-up comprising original mock-ups mimicking generic features of washing tanks (e.g. welds, folds, flat surfaces, air/liquid/wall interface) was designed. The flow pattern therein was characterized using two computational fluid dynamic calculation approaches. Full trials were run for 48 h at 10 degrees C with a Pseudomonas fluorescens strain to identify the preferential biofilm formation areas. As in current industrial systems, the pilot rig had recirculation areas and low wall shear stress rates (tau(w)<0.1 Pa) in corners and angles. These were identified as critical areas with Surface Microbial Loads (SML) over 5 Log(10)/cm(2). However, tau(w) alone failed to explain why SML in areas under unidirectional flow was higher than in the mock-ups. Lastly, air/liquid/wall interface conditions were more critical than immersed surfaces. This study validated the possibility of using CFD methods to understand the way in which flow pattern influences biofilm formation. The methodology proposed would be helpful in quantifying equipment components criticality based on biofilm growth parameters. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.