What Is Algin?
Alginic acid, found in brown algae like kelp and wakame seaweed, is a polysaccharide composed of two monosaccharides: ß-D-mannuronate (M) and α-L-guluronate (G). These are polymerized into a linear chain. In its pure form, alginate appears as a white to pale yellow fibrous, granular, or powdery substance at room temperature.
While pure alginate is insoluble in water, its alkali salts are water-soluble. It is insoluble in fats, oils, and organic solvents. The properties of alginate, such as gelation capacity and gel strength, depend on the M/G ratio and the arrangement of these components.
Uses of Algin
Algin and its derivatives are used in various applications, including food, pharmaceuticals, cosmetics, and textile processing. In food, it serves as a quality improver for flour products, thickeners, and stabilizers in items like ice cream and syrups. Algin’s gelatinizing properties are utilized in artificial salmon roe and flavor-trapping capsules, as well as in manufacturing adhesives, films, fibers, water-based paints, gelling agents, and paper bleed prevention.
In medicine, algin is used as a tablet disintegrant and in surgical threads, hemostatic agents, and ointments.
Principle of Algin
1. Algin Production Method
Algin is extracted from brown algae, such as kelp. The extraction process involves alkaline treatment, filtration, acid precipitation, and drying to obtain algin. The M/G ratio and the arrangement of mannuronic acid and gluronic acid vary depending on the source of seaweed.
2. Properties of Algin
Algin’s properties, including gel strength, are influenced by the M/G ratio and the molecular arrangement. Sodium alginate is water-soluble, forming a hydrogel with multivalent cations like Ca2+. It dissolves in alkali and forms acidic fibrous gels at low pH. The gel strength is primarily determined by the G block content.
Types of Algin
Algin is available as algin and various salts, including sodium, potassium, and ammonium alginate. These salts form viscous aqueous solutions in cold and hot water, while algin and calcium alginate are water-insoluble. Algin products are sold in small quantities for laboratory use and in larger quantities for commercial applications in food, pharmaceuticals, cosmetics, textile processing, and other industries.