A rheological characterization of semi-solid dairy systems

Dispersions of cross-linked starch in full fat milk, taken as models of custard model systems, have been characterized by different rheological means: viscoelastic measurements, classical flow measurements and ‘vane’ rheometry. From viscosity measurements, the flow behaviour was described within the shear rate range 0.01–100 s⁻¹. The flow curves were fitted using the Herschell–Bulkley equation over the shear rate range 0.1–100 s⁻¹ while a deviation was found towards the low shear rate range, making the determination of the yield stress non realistic. Instead, measurements with the ‘vane’ device in low shear conditions provided a way to estimate the yield stress, at rest and after shearing, but the entire flow curve was not described. From the viscoelastic measurements at low strain amplitude, the mechanical spectra were obtained. Linearity tests beyond the linearity limits provided the critical stress corresponding to the G′–G″ cross-over. The parameters obtained from these different rheological methods are discussed.