Agar from agarose (Agarose) and agar fruit (Agaropectin) composed of two parts, as a gelling agent agarose is a non-ionic polysaccharide does not contain sulfate (salt), is the formation of the gel component, the macromolecular chain chain linkage in the 1, 3 glycosidic bond alternately connected to the β-D-galactopyranose residues and 3, 6-α-L-galactopyranose residues. galactose residues. Agar pectin, on the other hand, is the non-gelatinous part and is a complex polysaccharide with sulfate esters (salts), glucuronic acid, and pyruvic aldehyde. Commercial agar generally has 2%-7% sulfate (salt), 0%-3% pyruvate aldehyde and 1%-3% methylethyl. In the industrial agar color from white to slightly yellow, with a gelatinous feel, no smell or have a slight characteristic odor, agar is insoluble in cold water, soluble in boiling water, slowly soluble in hot water.

Molecular formula: (C12H18O9)n

From the molecular formula, it can be known that agar is a kind of polysaccharide body extracted from seaweed. In its structure there exists an aldehyde acid structure, in which the aldehyde is structurally unstable and easily oxidized. During the heating process, part of the aldehyde structure is oxidized, so it leads to a change in structure, which also causes a change in color. As the number of aldehydes cannot be fixed each time the oxidation occurs, it also leads to a difference in color.