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Chemical Structure
Alginic acid, a Polysaccharide is composed of two types of Uronic acid:
Mannuronic acid unit (M) and Guluronic acid unit (G), which form three
kinds of polymer segments of blocks:
M blocks : comprised only of M-M bonding,
G blocks : comprised only of G-G bonding,
M&G random blocks : comprised of M-G random bonding,
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Differences in M/G ratio and block configuration account for the differences
in Alginate properties and functionality, especially in gelling capability and
gel strength. The M/G ratio is dependent upon such factors as the species
of seaweed, the part of the seaweed used, the harvest location, and the
harvest season.
The carboxyl groups within the M and G units are easily ion-exchanged,
and can react wiht several kinds of cations. This results in changes in
Alginate properties and functionality.
Utilizing these chemical reactions and the resultant changes in
functionality, alginates have many commercial applications such as a
thickening agent, as a gelling agent, a dispersion stabilizer, a texture co-
agent and as a filament or film former.
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