Modelling of Swelling by the Fluorescence Technique in Kappa Carrageenan Gels

Kappa (‐κ) carrageenan gels prepared with various carrageenan concentrations in pure water were completely dried and then swelled in water vapor. Steady state fluorescence measurements were performed using a spectrometer equipped with temperature controller. Pyranine was embedded in κ‐carrageenan gels as a fluorescence probe during gel preparation. The fluorescence intensity, I, increased exponentially as swelling time is increased for all gel samples. The increase in I was modelled using Li‐Tanaka equation from which swelling time constants, $τc$ and cooperative diffusion coefficients, $Dc$ were determined. It was observed that $Dc$ increased as the swelling temperature was increased. On the other hand at each temperature, it was seen that $Dc$ decreased as kappa carrageenan concentration was increased. Activation energies for swelling were obtained and found to be 57.4, 58.3 and $62.73 kJ mol−1$ for the gels with increasing amount of κ‐carrageenan content.