4. Physicochemistry of gelled media

4.1 Simple model gels

Gels are often defined as soft solids that are more or less deformable before breaking. From a structural point of view, the "simplest" gels are composed of a single polymer present in relatively low concentration in the solvent medium (typically less than 2% by weight for polysaccharides). The polymer macromolecules are linked together to form a three-dimensional network of infinite size, i.e. occupying the entire volume under consideration and presenting a fairly loose mesh filled with solvent. The vast majority of polymer gels used in food or cosmetic products are physical gels, i.e. the macromolecules interact with each other at junction zones, stabilized by low-energy interactions over a distance of several monomer units. The low-energy interactions (hydrogen,...