Associative phenomena in galactomannan-deacetylated xanthan systems |
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Authors: | Goycoolea F M Milas M Rinaudo M |
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Institution: | Centro de Investigación en Alimentación y Desarrollo, A.C., PO Box 1735, Hermosillo, Sonora, C.P. 83000, Mexico. fgoyco@cascabel.ciad.mx |
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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. |
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