Silica gel for food is a kind of inorganic polymer colloidal material, which is condensed by silicic acid. The main component is SiO2 · nH2O, which content is more than 98%. It is non-toxic and tasteless, and has stable chemical properties. Under normal conditions, it does not react with any acid base except caustic alkali and hydrofluoric acid. Because it is a colloidal structure, it has many micropores and a large specific surface area.