The Effect of Added Salt on Gelation by Divalent Metal Ions of Alginate Aqueous Solution

Abstract

The alginate is an anionic polysaccharide which is composed of 1, 4-linked β-D-mannuronic acid (M) and 1, 4-linked α-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 C. The salt concentration required for gelation of the alginate aqueous solution increases in the following order, SrCl2 < MgCI2. 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+. © 1993, The Chemical Society of Japan. All rights reserved.