What Is Sodium Alginate (E401)? Applications, Dosage, Alternatives & Specifications

Sodium Alginate, also known as Alginic acid, sodium salt, is a natural high-molecular-weight water-soluble polysaccharide extracted from brown algae. It is an important category of seaweed gum, with wide application value in the global food industry, pharmaceutical industry, cosmetic industry, and textile printing and dyeing industry. Its molecular formula is (C6H7O6Na)n, CAS number is 9005–38–3, EINECS number is 232–682–6, CNS number is 20.004, and INS number is 401. In terms of chemical structure, sodium alginate is a linear block copolymer composed of β-D-mannuronic acid (M-block) and α-L-guluronic acid (G-block) linked by 1,4-glycosidic bonds. The sodium alginate molecule carries a large number of carboxyl groups (-COO−), giving it anionic polyelectrolyte properties. It can undergo ionic crosslinking with divalent metal ions such as calcium (Ca2+) to form a calcium alginate gel (egg-box model). This is the most core functional characteristic of sodium alginate. Sodium alginate appears as a white to light yellow powder or granules, almost odorless and tasteless. It is insoluble in organic solvents such as ethanol, diethyl ether, and chloroform, but is readily soluble in water to form a viscous colloid solution. The pH of a 1% aqueous solution is typically 6–8, and viscosity is stable within pH 5–8. Sodium alginate solutions exhibit the shear-thinning property of non-Newtonian fluids and are relatively stable to heat, light, and air, although viscosity decreases when solutions are heated above 85°C. Sodium alginate is hygroscopic, so care must be taken to protect it from moisture during storage. Sodium alginate is a natural polysaccharide extracted from the cell walls of brown algae (such as kelp, giant kelp, Sargassum, and Ascophyllum). The raw material is renewable and produced in large quantities, making sodium alginate one of the most widely used food gums globally. Sodium alginate is known as the natural multifunctional seaweed gum and is the most widely used and largest-volume variety among alginate products.

(1% aqueous solution, 20°C)

Sodium alginate is recognized as a natural multifunctional seaweed gum, holding an irreplaceable position in the global food, pharmaceutical, daily chemical, and industrial fields. Its most outstanding core advantages lie in its unique calcium ion crosslinking gelation property, excellent thickening and stabilizing performance, and extremely wide application adaptability.