On the sol-gel transition insolutions of kappa-carrageenan.

The disorder-order transition, which takes place at the gelpoint of k-carrageenan solutions was monitored by optical rotation and light scattering measurements. The coincidence of both sets of experimental data affords good evidence that the sol-gel transition is accompaned by a conformational change. Transition temperatures were observed to be linearly dependent on the logarthm of the salt concentration and this result is explained by the formation of double helices. Heats of gelation were measured by differential scanning calorimetry. It was found that the enthalpy increases with ionic strength, which was ascribed to the occurrence of a secondary process in which double helices are assembled into larger aggregates.