1. Morphology: Sodium alginate is a white or pale yellow powder, almost odorless and tasteless.
2. Solubility: Sodium alginate is readily soluble in water, but insoluble in organic solvents such as ethanol, ether, and chloroform. When dissolved in water, it forms a viscous liquid. Sodium alginate powder becomes wet upon contact with water; the hydration of the particles makes their surface sticky, and the particles quickly clump together to form clumps. These clumps then slowly and completely hydrate and dissolve. If the water contains other compounds that compete with alginate, sodium alginate is even less soluble. Sugars, starches, or proteins in water will reduce the hydration rate of sodium alginate, prolonging the mixing time. A 1% aqueous solution has a pH of 6-8; its viscosity is stable at pH 6-9, and decreases when heated above 80℃.
3. Toxicity: Sodium alginate is non-toxic. According to Table A.2 of the national standard GB2760, sodium alginate can be used as a thickener in various foods in appropriate amounts as needed for production.
4. Binding with Other Ions: Among the metal salts of alginate, only Na, K, Mg, and ammonium ions are soluble in water; other metal salts are insoluble. Utilizing this property, contacting a colloidal solution of sodium alginate with calcium ions can form a calcium alginate gel. The gel formation process can be controlled by adjusting the pH value, selecting a suitable calcium salt, and adding a phosphate buffer or chelating agent.
5. Stability: Dry sodium alginate is quite stable when stored in a well-sealed container at 25°C and below. Sodium alginate solutions are stable at pH values between 5 and 9. The calcium gel formed by sodium alginate is a thermally irreversible gel.
