The effects of anionic surfactant sodium dodecyl sulfonate (SDSN) on the sol-gel transition of κ-carrageenan (κ-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 (cSDSN＜5 mmol•L－1), slightly promoted the gelation of κ-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 κ-CAR, but also formed a new ordered structure in the gel matrix of κ-CAR. The patterns of interactions between κ-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.

Key words: κ-carrageenan, surfactant, sol-gel transition, polysaccharide, sodium dodecyl sulfonate (SDSN)