Mobility of carrageenan chains in iota- and kappa carrageenan gels
Résumé
Gels of kappa carrageenan (κ-car), iota carrageenan (ι-car) and their mixtures at a polysaccharide concentration of C = 10 g/L were prepared by cooling solutions in the presence of different concentrations of KCl or CaCl2. The mobility of carrageenan (Car) chains at 20 °C was determined using fluorescence recovery after photobleaching (FRAP). Slow recovery of the fluorescence was observed for the gels showing that a fraction of the Car chains remained mobile. The fraction of mobile chains in the gels varied between 25% and 75% depending on the type of Car and the type and concentration of salt. The fraction of mobile chains in gels of different Car or in different types of salt was not correlated to the gel stiffness determined by oscillatory shear measurements. The release of Car from gel fragments into excess solvent at the same salt concentration was probed as a function of time with light scattering. It was found that the released Car chains were on average smaller than those remaining in the gel.