Effects of SDS on the sol–gel transition of konjac glucomannan in SDS aqueous solutions

The interaction between konjac glucomannan (KGM) and an anionic surfactant, sodium dodecyl sulfate (SDS) is studied by rheological, circular dichroism (CD), conductivity, electron spin resonance (ESR), and FT-IR measurements. Since KGM is a neutral polysaccharide and has no significant hydrophobic side groups, the critical micelle concentration value of SDS is not influenced with the addition of KGM, and no marked binding occurs between them. SDS makes no conformational changes of KGM with or without heat treatment. The weak alkaline character of SDS induces the deacetylation of KGM chains and makes it form gels with heat treatment. At the same pH value, the gelation time needed for KGM by using SDS as the coagulant is shorter than that by using Na₂CO₃. The addition of SDS promotes the gelation process of KGM, indicating that although the interaction is weak, SDS micelles seem to play an important role in the gelation of KGM.