Agar disperses very easily in boiling water to form a sol, is insoluble in cold water but can absorb water and swell into gel-like lumps; the sol solution exhibits a neutral reaction. It is not broken down by enzymes during digestion and therefore has almost no nutritional value. Agar disperses readily in hot water, and even at a low concentration of 0.5%, it can form a firm gel. A 1% agar sol solidifies at 42°C, and the resulting gel does not melt even at 94°C, exhibiting strong elasticity. The gelation temperature of agar sol is relatively high, typically forming a gel at around 35°C. Agar has high water absorption and water retention capacity; when dry agar is soaked in cold water, it gradually absorbs water, swells, softens, and can absorb more than 20 times its weight in water. Agar gels have strong heat resistance. Agar is more acid-resistant than gelatin and starch, though less so than pectin. Agar can be used as a food thickener, a sizing agent for silk, a laxative, and as an adhesive, thickener, and capsule material in pharmaceuticals. It can also serve as a bacterial culture medium, a carrier for immobilized enzymes, a material for bacterial encapsulation, and a medium for electrophoresis. Additionally, it can be used for the filtration and separation of viruses, subcellular particles, and macromolecules, as well as for the observation of serum antigens or antibodies. The ADI (Acceptable Daily Intake) requires no special specification.
K2211080