Modelling Of The Mechanical Behaviour Of Cheese During Bubble Growth: An Experimentally Validated Approach

International audience; The growth of gas bubbles is a key phenomenon occurring in the making of Swiss-type cheeses. To achieve a better understanding of the formation of eyes in cheese, comprehensive knowledge of the transport phenomena involved is required. The aim of the present study was to investigate the momentum transport occurring during bubble growth. A generalised Maxwell model was used to describe the mechanical behaviour of the material. A specific method was developed to identify the model parameters by fitting the model to experimental stress relaxation curves. Those parameters were then used in a numerical model reproducing the growth of a single bubble and involving only momentum equilibrium and material behaviour. The driving phenomena for the growth of the bubble were the applied pressure at the bubble–cheese interface and the gravity. Such configuration was reproduced experimentally as closely as possible. A cylinder containing a single bubble was isolated from the cheese block and enclosed inside a sustaining apparatus made of plastic that prevented the external boundaries of the cylinder from moving. The upper surface of the cheese cylinderwas let free. A needle was inserted at the basement of the cylinder and gas was injected inside the bubble at t = 0. Pressure internal to the bubble was then monitored and bubble volume, aswell as deformation of the upper surface of the cylinder, were dynamically assessed by Magnetic Resonance Imaging within the same experiment. These data were compared to simulation with the objective of validating the adequacy of the mechanical model (structure, model parameters) to the case study of bubble growth. The results showed that the proposed model is able to describe the growth of a single bubble satisfactorily. It also appeared that the growth of the bubble is driven mainly by the viscous part of the viscoelastic model. This study encourages further investigation on the other phenomena implicated in bubble growth, such as gas production in the cheese and its transport from the material to the bubble by gas diffusion.