alginates

Alginates are a family of natural polysaccharides derived primarily from brown seaweeds (Phaeophyceae). They consist of long chains of two uronic acids, β-D-mannuronic acid (M) and α-L-guluronic acid (G), arranged in blocks with varying compositions. The salts of alginic acid, known collectively as alginates, are commonly used in industry in forms such as sodium alginate and calcium alginate. Gelation occurs when divalent cations, especially calcium, cross-link the G-block regions to form a hydrogel; this process is frequently described by the egg-box model.

Commercial extraction involves alkaline treatment of seaweed to solubilize alginate, followed by filtration, precipitation, and drying to produce alginate products. The physical properties—viscosity, gel strength, and gelling behavior—depend on molecular weight and the M/G ratio, as well as the countercation (for example sodium vs. calcium). Alginates are valued as hydrocolloids for thickening, stabilizing, and forming gels, with calcium alginate gels typically offering stronger networks and sodium alginate solutions providing higher viscosity.

Applications of alginates span food, medicine, and biotechnology. In foods, they act as thickeners and gelling agents. In dentistry, alginate formulations are used for impression materials. In wound care, alginate dressings form moist gels that support healing and manage exudates. They are also used for cell immobilization and in drug delivery systems. Alginates are generally regarded as safe for many uses, though regulatory status and specific applications vary by jurisdiction.