ORIGINAL CONTRIBUTION Effects of SDS on the sol–gel transition of konjac glucomannan in SDS aqueous solutions Wanchun Yin & Hongbin Zhang & Long Huang & Katsuyoshi Nishinari Received: 6 October 2007 / Revised: 21 November 2007 / Accepted: 21 November 2007 / Published online: 10 December 2007 # Springer-Verlag 2007 Abstract 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 Na 2 CO 3 . 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. Keywords Konjac glucomannan . Sodium dodecyl sulfate . Conformational transition . Critical micelle concentration . Micelles Abbreviations KGM konjac glucomannan SDS sodium dodecyl sulfate CD circular dichroism ESR electron spin resonance cmc critical micelle concentration cac critical aggregation concentration PDMAEMA poly(2-(dimethylamino)-ethyl methacrylate) PEO poly(ethylene oxide) HMHEC hydrophobically modified (hydroxyethyl) cellulose HPMC hydroxypropyl methyl cellulose Introduction Considerable efforts have been devoted toward studying the interactions between surfactants and polymers in solutions, which are not only for scientific interests, but also for industrial applications, such as in foods, pharmaceuticals, cosmetics, paints, coatings, detergents, tertiary oil recovery [1–3]. The interactions between surfactants and some poly- saccharides [4–10] have also been reported; however, the interaction between surfactants and konjac glucomannan (KGM), which is a neutral polysaccharide and also has various applications in foods, pharmaceuticals, coating [11– 13], has never been studied. Derived from the tuber of Amorphophallus Konjac C. Koch [11], KGM is composed of β-(1→4) linked β- D-mannose and β-D-glucose in a molar ratio of 1.6:1 [14, Colloid Polym Sci (2008) 286:663–672 DOI 10.1007/s00396-007-1810-x DO01810; No of Pages W. Yin : H. Zhang (*) : K. Nishinari Department of Polymer Science and Engineering, School of Chemistry and Chemical Technology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, People’ s Republic of China e-mail: hbzhang@sjtu.edu.cn L. Huang Danisco (China) Co., Ltd, Kunshan 215300, People’ s Republic of China K. Nishinari Department of Food & Nutrition, Faculty of Human Life Science, Osaka City University, Sumiyoshi, Osaka 558-5858, Japan