The gelling of κ-carrageenan in light and heavy water

Gels of κ-carrageenan were prepared in H₂O and D₂O. Rheological measurements revealed that in heavy water the elastic modulus is substantially higher. From the rheological view point, this result indicates the formation of a higher number of physical-crosslinking points in the structure of the gel. These crosslinking points are mainly associated with the aggregation of the double-helix of the κ-carrageenan, which is enhanced in D₂O. The thermal stability of the gels in both solvents (relative to the sol-gel transition) was also investigated by using polarimetric measurements (to measure the relative fraction of helix-coil) and micro-differential scanning calorimetry (micro-DSC). The results obtained using these techniques are very consistent and allow us to propose a model to explain the differences for the gels formed in light and heavy water based on the degree of double-helix aggregation.