Ultrasound assisted cold gelation of kappa carrageenan dispersions

Usually to prepare a gel from kappa carrageenan, an aqueous dispersion of carrageenan powder is heated. This research presents evidence of cold gelation of carrageenan dispersions while no heat is needed. The occurrence of cold gelation is investigated in the absence or presence of potassium ions during ultrasound treatment by studying the mechanical and microstructural properties of the prepared gels using a texture analyzer and scanning electron microscopy, respectively. Carrageenan gels were obtained by applying power ultrasound. By increasing sonication time, gel hardness increased up to a certain level (in absence or presence of K+ during ultrasound treatment) and further ultrasound application had a negative effect. Moreover, the mechanical properties of the gels in which K+ ions were added before ultrasound were weaker than the samples when K+ ions were added after sonication. Relaxation times of gels were calculated using the generalized Maxwell model with three elements.