Jury:

Rapporteurs :

• Emmanuel Le Clézio, Professor, University of Montpellier
• Romain Jeantet, Professor, Agrocampus Ouest

Examiners :

• Guy Feuillard, Professor, INSA Centre Val de Loire
• Marieke Van Audenhaege, Research Officer, Head of the Dairy Technology Unit, SODIAAL
• Guillaume Delaplace, Director of Research, INRA
• Dorothée Callens-Debavelaere, Senior Lecturer, Université Polytechnique Hauts-de-France
• Pierre Campistron, Senior Lecturer, Université Polytechnique Hauts-de-France

Thesis supervisor :

• Emmanuel Moulin, Professor, Université Polytechnique Hauts-de-France

Summary:

Fouling of equipment occurs in many industrial sectors. For example, contamination of food contact surfaces caused by fouling results in considerable economic losses and increased public health risks. Fouling is generally cleaned using highly polluting chemicals. It is therefore important to develop devices that can monitor the formation/elimination of fouling on these surfaces (without disrupting production) in order to reduce the microbiological risks and the environmental and economic impacts associated with cleaning processes. This work focuses on the detection of the fouling factor using a non-invasive ultrasonic method known as coda wave interferometry (CWI). This technique has been tested for different types of application (wax cleaning, detection of biofilm formation and cleaning of protein deposits). The results obtained are very promising and show that CWI is capable of detecting even a slight change in the fouling factor. In particular, the evolution of the decorrelation coefficient for each application shows good agreement with the actual fouling state of the surface. Overall, this work provides a body of evidence showing that the CWI method is applicable to monitoring the fouling factor of deposits on solid surfaces.