Influence of thermal history on the stability of gelatin gels.

Gelatin gel properties have been studied using three techniques. Optical rotation measurements have shown that the lower the ageing temperature, the faster the helix content increases but the lower the helix stability. Rheological measurements show that a small increase in temperature leads to a melting of some junction zones followed by a build up of new ones. By ageing the gel at two successive temperatures one can show the existence of two populations of junction zones with different thermal stabilities. The same result is shown on melting thermograms obtained by differential scanning calorimetry. All these results are consistent with the hypothesis of the presence of junction zones of various lengths, the thermostability of which being proportional to their lengths.