Rheological monitoring of structure evolution and development in stirred yoghurt

The objective of the present work was to study the rheological changes of yoghurt at different stages in the manufacturing process and to try to gain some measure of understanding of the morphological changes that occur. Rheological measurements were made on yoghurt samples for different post-sampling periods, allowing the study of the influence of time in the structure and flow properties of the material to be performed. This was accomplished using both steady and oscillatory rheometry. Up and down shear rate sweeps, constant and oscillatory shear measurements were carried out. The study of the effect of temperature allowed the observation of two distinct regions of temperature dependency, in all samples, the transition point, being approximately 25 degrees C. The structural and rheological changes that occurred during post-incubation were observed during the analysis of several yoghurt samples, indicating that there is a partial structure recovery upon cessation of flow. (C) 2000 Elsevier Science Ltd. All rights reserved.