Critical Exponents of Kappa Carrageenan in the Coil-Helix and Helix-Coil Hysteresis Loops

The steady-state fluorescence technique was used to study coil-helix (sol-gel) and helix-coil (gel-sol) transitions of the kappa carrageenan-water system with various carrageenan contents. Fluorescence (I) and scattered light (Isc ) intensities were measured against temperature to determine critical phase transition temperatures and exponents. It was observed that the coil-helix transition temperatures, Tch were much lower than the helix-coil (Thc ) transition temperatures due to the hysteresis of the phase transition loops. The gel fraction exponent (β) was measured and found to be in accord with the classical Flory-Stockmayer model.