Setting up laboratory tools and beginning modelling work

In order to determine the ability of L. monocytogenes to resist water stress, a protocol for dehydrating Listeria in a hyperosmotic environment was developed.

For further work under conditions close to those found in the field, we wanted to find out whether contaminants could be replaced by laboratory media with a more standardized composition. Contaminants and media were compared in terms of growth, structure, and relative adhesion forces of populations cultured on stainless steel.

Finally, the feasibility of using a material that is difficult to clean and therefore likely to provide a habitat for persistent bacteria was verified on the basis of the reproducibility of weakly and strongly adherent bacterial populations.

The numerical modelling work undertaken to predict the climatic conditions to which bacteria on surface areas in a workshop are subjected requires validation at laboratory and industrial workshop scales. To this end, a test cell has been set up to measure the air speed, humidity and temperature near a wet wall, as well as the kinetics of water evaporation from the wall itself. Such measurements have already been carried out in the selected industrial workshop. The kinetics of water evaporation from wet surfaces under different environmental conditions have been measured to incorporate this process into the numerical models. Energy optimisation of air dehumidification is being addressed by studying the use of liquid desiccants and searching for equations that describe liquid/vapour equilibria.