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Physical properties of xanthan, galactomannan and their mixtures in aqueous solutions
Author(s) -
Rinaudo M.,
Milas M.,
Bresolin T.,
Ganter J.
Publication year - 1999
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.19991400113
Subject(s) - galactomannan , isothermal microcalorimetry , aqueous solution , circular dichroism , chemistry , random coil , helix (gastropod) , crystallography , polymer chemistry , enthalpy , polysaccharide , thermodynamics , organic chemistry , physics , ecology , biology , snail
Some new information on the conformation of xanthan in aqueous solutions is given. A single helical chain conformation characterizes xanthan in the native state. When heated over the critical temperature for conformational change ( helixŕ coil), the xanthan is denatured and renatured when it is cooled down in a localy double helical structure. A galactomannan was also characterized and its persistence length was obtained (Lp ≈ 90A°). Then mixtures of the galactomannan and xanthan were investigated to propose a mechanism for the specific gelation. From the results of microcalorimetry and circular dichroism, it is concluded that a complex is formed between one disordered xanthan chain and one galactomannan chain and that an ordered conformation is stabilized at temperatures lower than 25°C when the galactomannan has a M/G ratio of ≈ 3. This temperature corresponds to the sol‐gel transition. This is the first time that a structure of the crosslink points is demonstrated.