Ricerc@Sapienza

The combination of many forces exerts a key role in the stabilization of colloidal dispersions, in controlling attraction or repulsion among the dispersed entities. Such forces concur to stabilization, phase separation, coagulation, and are particularly evident in water-based systems. Their combination favors/hinders the association of colloids, and is often met in food sciences. The results one gets arise from the combination of van der Waals, electrostatic, sterical, osmotic and so forth. Some of them are attractive, other repulsive. Their combination ensures the onset of a given organization mode, as phase separation, if the repulsive forces dominate. Obviously, changes in the relative weight of such contributions favor aggregation or, conversely, dispersion. A worked example based on common knowledge is the milk manipulation chain, leading to cheese formation. That process arises from the combination of effects leading to aggregation, or, conversely, phase separation of casein and other milk components. Finally, maturing gives rise to fresh or seasoned cheese. The combination of attractive, van der Waals, vdW, and repulsive, as double layer, DL, but also sterical, ST, depletion and osmotic forces results in the dominance of aggregation versus dispersion modes. The overall effect depends on the concentration of colloid particles, on the forces amplitude, on their decay length and power laws. The combined role of such forces is at the basis of the well-known DLVO theory on colloid stability. The results predicted by that theory are finely tuned when vdW and DL forces overlap with sterical stabilization and, eventually, with depletion ones. The milk manipulation chain is a worked example of such intriguing association features. The different stages that are pertinent to each preparation step imply the dominance of one, or more, of those forces leading to the production of a selected cheese kind.