However, upon
interaction with divalent metal ions-such as Ca2+-they
form an ordered structure. Grant et al. showed that the
gelation process involves cooperative binding of calcium
ions between aligned GG blocks of two alginate chains
(6).
The gelation of calcium alginate is an almost instantaneous
and irreversible process, which is governed by
the relative rate of diffusion of calcium ions and polymer
molecules into the gelling zone (7, 8).
This fact indicates
that the gelation process can be accurately expressed
by the relationships used for other diffusion-limited
reaction systems (9-12).