Starch consists of about 80% gum starch and about 20% sugar starch. Its basic unit is α-D-glucopyranose, molecular formula for C6H12O6. starch has straight chain starch and branched chain starch two types. The former is unbranched helical structure; the latter to 24~30 glucose residues to α-1,4-glycosidic bonds connected to the first and last, in the branched chain at the α-1,6-glycosidic bonds.

Starch consists of about 80% gum starch and about 20% sugar starch. Its basic unit is α-D-glucopyranose, and its molecular formula is C6H12O6. starch has two types: straight-chain starch and branched-chain starch. The former is unbranched helical structure; the latter to 24~30 glucose residues to α-1,4-glycosidic bond head to tail and become, in the branched chain at the α-1,6-glycosidic bond.