Gelation of gelatin solution.

In order to study the gelling mechanism of gelatin, the phase diagram for a diluted gelatin solution was investigated. Phase boundary curves were obtained by measuring the fluorescent depolarization, optical rotation, reduced viscosity, and light scattering of the gelatin solution. The phase diagram obtained exhibited similar features to those for amylose and agarose gelling systems. Fromthis similarity, the gelling mechanism of gelatin is concluded to be as follows: The randomly coiled gelatin molecule in hot solution partially recovers a collagen fold at the denaturation temperature near 40°C on cooling. This gelatin state is presumed to correspond to the interrupted helical form for amylose. This partial helical solution then separates into two phases, a dilute solution and a coacervate consisting of a concentrated solution, at a phase separation temperature which depends upon the gelatin concentration. When the concentration is sufficiently high, coacervate particles are connected with each other to form a three dimensional macroscopic network, and the solution loses its fluidity to become a gel.