Effects of Sodium Dodecyl Sulfonate on the Sol-gel Transition of κ-Carrageenan

The effects of anionic surfactant sodium dodecyl sulfonate (SDSN) on the sol-gel transition of kappa-carrageenan (kappa-CAR), an anionic polysaccharide, have been investigated by different techniques including rheology, differential scanning calorimetry (DSC) and UV-Vis spectrometry. It has been found that, SDSN, at low concentrations (C-SDSN < 5 mmol.L-1), slightly promoted the gelation of kappa-CAR due to a weak salt-out effect, whereas at higher concentrations (c > 5 mmol.L-1), SDSN not only obviously decreased the sol-gel transition temperature of kappa-CAR, but also formed a new ordered structure in the gel matrix of kappa-CAR. The patterns of interactions between kappa-CAR and SDSN were discussed. And a mechanism of cooperative interactions of electrostatic repulsion, competition for K+ and hydrophobic interaction has been proposed to interpret the experimental results.