THE EFFECT OF ADDED SALT ON GELATION BY DIVALENT METAL-IONS OF ALGINATE AQUEOUS-SOLUTION .................

The alginate is an anionic polysaccharide which is composed of 1, 4-linked beta-D-mannuronic acid (M) and 1,4-linked alpha-L-guluronic acid (G). It is well-known that a sodium alginate aqueous solution forms a gel by introducing divalent metal ions. In the present study, the effect of added salt on the gelation by divalent metal ions is investigated by way of rheological measurements using a cone-plate type rheometer at 25-degrees-C. The salt concentration required for gelation of the alginate aqueous solution increases in the following order ; SrCl2<CaCl2<MgCl2. This result is strongly related to the fact that the affinity of divalent metal ions for the alginate decreases in the following order ; Sr2+>Ca2+>Mg2+.