Gelation of kappa carrageenan as studied by electron spin resonance spectroscopy

Abstract

Experiments have been carried out to study the thermally induced gelation of kappa carrageenan using electron spin resonance spectroscopy (ESR). Nitroxide spin probe experiments have suggested that the gel is comprised of aggregated polymer chains and that it contains large pockets of mobile solvent. The spin labelling technique used to monitor the molecular motion of the polymer chains themselves has indicated that the gel exists as a two-phase system containing precipitated aggregates dispersed within a homogeneous solution of dissolved molecules. The proportion of molecules in each phase has been calculated by computer analysis of the ESR spectra. Further evidence for the existence of a two-phase system was gained by centrifuging the gel. The supernatant removed was found to contain about 28% of the total carrageenan and intrinsic viscosity measurements showed that it consisted of molecules with a lower average mol. mass than the original starting material. Analysis showed that chemical fractionation had also occurred on gelation.