Alginate (sodium alginate) is a natural polysaccharide extracted from brown algae. At room temperature, it appears as a white to pale yellow powder or granules, readily soluble in water to form a viscous colloid. Its aqueous solution exhibits a unique thixotropic property (becoming thinner under agitation and thickening again when stationary). Chemically, it is a linear polysaccharide composed of β-D-mannuronic acid and α-L-guluronic acid. The carboxyl groups on its molecular chain allow it to undergo ionic cross-linking with polyvalent metal ions (such as calcium ions), forming a thermo-irreversible gel. Based on these properties, its primary use is as a safe food additive (thickener, stabilizer, gelling agent) in the production of products like jelly, ice cream, and yogurt. It is also widely applied in pharmaceuticals (sustained-release formulations, wound dressings), textile printing and dyeing (printing paste), dental impressions, tissue engineering, and other fields.