Gels, of gelatine

The gel of gelatine differs from that of silica in that in the former the sol-gel transformation is reversible and not in the latter. The coalescence of the amicrons of gelatine to form streptococcic fibrils occurs at low temperatures, a process readily reversed by elevation of the temperature which decreases the amount of adsorbed water, increases the mobility of the fibrils, and permits of their rupture into smaller units. Gelatine is thus readily rendered more disperse by water. 

A dispersion in the form of a suspension or polymer solution that behaves as an elastic solid or semi-solid rather than a liquid. A dried-out gel is termed a xerogel. Examples gels of gelatin solutions or of clay suspensions. 

Walkenstrom, P., and Hermansson, A.M. (1997a). High pressure treated mixed gels of gelatin and whey totems. Food Hydrocolloids, 11, 195-208. 

Upon cooling more rapidly, the droplets became smaller and smaller and finally microscopically unresolvable structures were obtained. If the concentration of the gelatin exceeded 36 %, not the droplets separating solidified, but the liquid in which they were dispersed. The gel formed consisted of a solid structure formed by the latter and in which numerous liquid droplets remained enclosed. These experiments, however, only show that a gel of gelatin may be formed in this way and have the structure set forth here. They do not prove that all gelatin gels belong to this type. The former represent typical systems of composite nature, in the sense as explained in Chapter I of this volume. 

Fig. 1(a) OZ plot of quasi-dilute solution (quasi-gel) of gelatin [24]. 

Manipulation of the temperature or pH, or addition of multi-valent metal ions to dilute polymer solutions are common techniques for creating hydrogels, but these fall outside of conventional superabsorbent technology. Gels of gelatin, certain natural gums, and sodium silicate are not the same as superabsorbent polymer gels. The key difference Is spontaneity. The former require assistance to gel while the latter form gel merely upon exposure to water. 

---