title: Atomic force microscopy studies on heat-induced gelation of curdlan.
abstract: Heat-induced gelation of a cold-water insoluble polysaccharide, Curdlan, was investigated using atomic force microscopy (AFM). Curdlan dissolved into NaOH aqueous solutions exhibited a spectral transition around 0.2 mol/L NaOH, which is an indicative of conformational transitions from a single helix at a lower alkali concentration to a disordered chain at a higher concentration. Nevertheless, AFM images of Curdlan solubilized in 0.01 mol/L NaOH revealed the presence of heterogeneous supramolecular assemblies of Curdlan: the majority of the molecules were in the form of microfibrils, the lengths of which were on the order of micrometers and the cross-sectional heights of which were approximately 2-3 nm, whereas single molecular chains, partially dissociated from these microfibrils, were also observed. Heating such a sol resulted in the formation of densely cross-linked microgel networks. Heat-induced gelation of Curdlan appears to be initiated by partial dissociation of single chains from supramolecular microfibrils and followed by cross-linking of microfibrils via hydrophobic interactions among these partially dissociated chains.
authors.affiliation: Department of Food and Human Health Sciences, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan. ikeda@life.osaka-cu.ac.jp
authors.forename: Shinya
authors.initials: S
authors.lastname: Ikeda
authors.forename: Yuka
authors.initials: Y
authors.lastname: Shishido
mesh_terms: D005782:Gels / Q000737:chemistry*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D018625:Microscopy, Atomic Force; D013057:Spectrum Analysis; D047071:beta-Glucans / Q000737:chemistry*
chemical_list: D005782:Gels; D047071:beta-Glucans; C038459:curdlan