Na- and K-alginate; effect on Ca2+ -gelation

The effect of two different monovalent alginate counterions has been studied in Ca2+ -mediated sol/gel transitions and in Ca2+ -gels at apparent equilibrium for alginates with different chemical composition and sequence. K-alginates were generally found to undergo faster sol/gel transitions compared...

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Bibliographic Details
Published in:Carbohydrate polymers 1998, Vol.35 (1/2), p.1-6
Main Authors: Draget, K.I, Steinsvag, K, Onsoyen, E, Smidsrod, O
Format: Article
Language:English
Subjects:
alginates
Applied sciences
calcium
Exact sciences and technology
gelation
guluronic acid
inorganic ions
Laminaria
modulus of elasticity
Natural polymers
Physicochemistry of polymers
potassium
sodium
Starch and polysaccharides
uronic acids
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Summary:The effect of two different monovalent alginate counterions has been studied in Ca2+ -mediated sol/gel transitions and in Ca2+ -gels at apparent equilibrium for alginates with different chemical composition and sequence. K-alginates were generally found to undergo faster sol/gel transitions compared to the Na-alginate. At apparent equilibrium and at low Ca2+ concentration, Na-alginate gels showed reduced elastic moduli compared to the K-alginates. The relative differences both in sol/gel transition kinetics and modulus at apparent equilibrium increased with increased content of guluronic acid residues in the alginate sample. Increasing the amount of internally released Ca2+ from 15 to 30 mM resulted in equal elastic properties at apparent equilibrium suggesting that dissimilarities in ion exchange reactions between Ca2+/Na+ and Ca2+/K+ is the main driving force. The specific effect of one of the counterion could be reversed by adding increasing amounts of the other. Selectivity coefficient determinations for alginates revealed a slight enhanced binding of Na+ compared to K+, most probably due to the guluronate residues.
ISSN:0144-8617
1879-1344
DOI:10.1016/S0144-8617(97)00237-3