Rheological characterisation of semi-hard cheese using lubricated squeezing flow test

In semi-hard cheeses, the pressure increase occurring during eye growth can create cracks leading to product downgrading. Rheological properties of semi-hard cheeses were investigated using lubricated squeezing flow (LSF), a test specifically chosen to mimic conditions as close as possible to the real eye growth in cheese. Flow curves showed a power law profile, characteristic of a shear-thinning behaviour. Moreover, stress/strain curves obtained at a constant biaxial extension rate showed a strain-hardening behaviour. Structural changes in the matrix during eye growth giving higher resistance towards deformation were indicated, and a schematisation of microstructure changes due to eye growth was postulated. Some threshold values were also identified during ripening, such as the biaxial yielding stress and strain; these were not impacted by cheese age or by the anisotropic organisation of the matrix. However, the yielding strain and Young's modulus increased with the biaxial extension rate.