Anna Rzepiela from Wageningen University simulated the influence of shearing and tensional forces on the structure of cheese. Dairy products are subjected to various forces during the production process, packaging phase and the transport phase. These forces modify the characteristics of the product. A new model describes these processes more accurately.
Eventually the researchers would like to simulate the combined effect of all of these forces on the cheese. For example, it would then be possible to describe what happens to cheese when it is chewed.
Cheese is a so-called particulate gel, a system of particles that form a weakly-bound network in a liquid environment. Cheese consists of long strands of casein and whey proteins in an environment of whey. Whey is the thin, sweet fluid that remains once the curds have been separated from the milk. The long strands are bound together and form a strong network.
When cheese is pulled apart, the bonds between the particles are broken and the structure of the cheese changes. The model previously used by the researchers assumed that a force applied to the surface of the cheese penetrated directly to deep inside the cheese. However, Rzepiela's model only includes the surface forces. The tensions in the network then transmit the forces further. This model is a better approximation of the real situation.
The chemist simulated an experiment in which the cheese is clamped between two parallel plates that slide backwards and forwards along the cheese surfaces. The quicker the plates move the greater the deformation, and thus the greater the damage to the cheese.
The old model always predicted the same structural changes, independent of the number of bonds between the strands and the location of these. However, experiments have shown that the nature and location of the damage was dependent on the structure of the particulate network. The new model can better predict these differences.
For further information please contact Anna Rzepiela MSc (Mathematics and Statistical Methods Group, Wageningen University), tel. 31-317-483-550, e-mail: anna.rzepiela@wur.nl or assistant supervisor Dr J.H.J. van Opheusden, tel. 31-317-483-286. The doctoral thesis will be defended on 15 April 2003. Ms Rzepiela's supervisor is Prof. J. Grasman. The research was funded by the Netherlands Organisation for Scientific Research.