Molecular origin for rheological characteristics of native gellan gum

The (1)H-nuclear magnetic resonance spectrum showed that the l-rhamnosyl residues of native gellan gum were coinvolved in both a small number of (4)C(1)-pyranose conformations and a large number of (1)C(4)-pyranose conformations, whereas for deacylated polymer, almost of the residues were involved in (4)C(1)-pyranose conformation. The flow curves of native gellan gum showed plastic behavior above 0.2%. The elastic modulus stayed at a constant value with increase in temperature up to 40 A degrees C, then decreased rapidly. The elastic modulus increased with addition of CaCl(2) (6.8 mM) and stayed constant value with increase in temperature up to 65 A degrees C, then decreased rapidly. The stronger elastic modulus was observed in deacylated gellan gum with addition of CaCl(2). The elastic modulus of native gellan gum showed larger value than that in aqueous solution in the presence of urea (4.0 M). Intra- and intermolecular associations of native gellan gum molecules in the presence of Ca(+2) were proposed.