Design of a multi-scale texture study of yoghurts using rheology, and tribology mimicking the eating process and microstructure characterisation
Résumé
Physical properties of 13 yoghurts were investigated combining rheology, tribology, particle size measurements and confocal laser scanning microscopy. New protocols were designed to improve mimicking of the eating process. In addition to classically acquired rheology properties, viscosity was measured under a constant shear rate and increasing temperature from 10 degrees C to 25 degrees C, corresponding to in-mouth conditions before swallowing. For friction measurement, force load and velocity were determined to be discriminating and relevant to oral conditions. Friction coefficient was the only instrumental indicator significantly correlated to fat content; viscosity was mostly linked to protein content even at high concentrations. Moreover, tribology and rheology indicators were uncorrelated with one another, bringing complementary information. The combination of oral-process-mimicking protocols and microstructure evaluation, performed on products purposely covering wide ranges of fat (0-10%, w/w) and protein (3-10%, w/w) content, allowed good characterisation of such diversity through a multi-scale approach.