Thixotropic Characterization of Non Fat and Full Fat Stirred Yoghurt

The objective of this present work was to study the effects of shear rate and temperature on the time dependency of two types of stirred yoghurt (non fat and full fat) under constant shear rate. The experimental data was measured using a rotational viscosimeter Viscotester VT550, Searle type, in which the outer cylinder is fixed and the inner cylinder rotates. Rheological data was obtained at different temperatures (10, 20 and 30 ºC) and three different shear rates (50, 200 and 445 s-1), likewise the shearing time was fixed to 8000 s. In this work, it was demonstrated that samples exhibited a thixotropic behaviour, which increased with the shear rate and decreased with the temperature. The experimental data were fitted with Weltmann, Hahn, First order stress decay and Second order structural kinetic models. The best adjustment was obtained with the Weltmann model.

کلیدواژه ها:

stirred yoghurt ، time dependent viscosity ، thixotropy ، rheology