title: Associative phenomena in galactomannan-deacetylated xanthan systems.
abstract: The interaction between mesquite seed galactomannan (MSG; D-mannose to D-galactose ratio (M/G) approximately 1.1) and deacetylated xanthan (DX) in 5 mM NaCl leading to synergistic gel formation at 25 degrees C was investigated and compared with the far more studied system made of xanthan and locust bean gum (LBG; M/G approximately 3.5). Rheology and differential scanning calorimetry were used to measure temperatures of gel formation and transition enthalpy as a function of polymer composition, while circular dichroism was used to probe the conformation of DX in the LBG-DX system. MSG and DX associate at 25 degrees C with a well defined stoichiometry of 0.6:1.0 (w/w) at low ionic strength favouring the disordered coil state of DX. When LBG was used in place of MSG in water or 5 mM NaCl, two types of mechanisms of interpolymeric association are envisaged.
authors.affiliation: Centro de Investigación en Alimentación y Desarrollo, A.C., PO Box 1735, Hermosillo, Sonora, C.P. 83000, Mexico. fgoyco@cascabel.ciad.mx
authors.forename: F M
authors.initials: FM
authors.lastname: Goycoolea
authors.forename: M
authors.initials: M
authors.lastname: Milas
authors.forename: M
authors.initials: M
authors.lastname: Rinaudo
mesh_terms: D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D005690:Galactose / Q000031:analogs & derivatives; D008351:Mannans / Q000737:chemistry*; D008956:Models, Chemical; D011108:Polymers / Q000737:chemistry; D011135:Polysaccharides, Bacterial / Q000737:chemistry*; D011487:Protein Conformation; D012965:Sodium Chloride / Q000494:pharmacology; D013696:Temperature
chemical_list: D008351:Mannans; D011108:Polymers; D011135:Polysaccharides, Bacterial; C012990:galactomannan; D012965:Sodium Chloride; C002563:xanthan gum; D005690:Galactose