Due to his peculiar behaviour Alginate is one of the most significant of all hydrocolloids used in food.
Commercial applications for Alginates in foods are based on the interaction between sodium Alginate and cations to generate or modify food rheology, normally by the formation of a gel network at any temperature in presence of calcium cations: the divalent calcium cation cross link the alginate polyanionic macromolecules. Once formed, the gel is thermo irreversible, maintaining his shape and structure through thermal processes.
Crucial is the control of the kinetics of calcium release.
Alginates occur in the intercellular space of brown seaweeds, and provide both strength and flexibility to these water plants, Alginates are high molecular weight polymers made of mannuoric acid (M block) and Guluronic acid (G block). The higher the number of poly-G blocks, the stronger the gel formed in presence of calcium, vice versa when regions of M blocks dominates Alginate will not gel even in presence of calcium, but will provide viscosity.
The viscosity is determined by the length of alginates molecules