Amylopectin

Starch is composed of two polymers of different structure; amylose is essentially linear, whereas amylopectin is a branched component.

The amount of amylopectin varies among different starches. Waxy varieties contain almost 100% amylopectin. Starch normally contains about 20–30% amylose and 70–80% amylopectin.

Amylopectin is a branched-chain polymer, the branch points occurring through a-1,6 glycosidic bonds.

The estimation of the chain length distribution is of primary importance for characterizing the molecular structure of amylopectin.

The branched amylopectin molecule contains regions with low and high levels of branches. In highly branched regions, side-chains of amylopectin are grouped, forming crystalline zones (clusters).

Crystalline region is less susceptible to enzymatic hydrolysis, water penetration, and other chemical reactions than amorphous region.

Side chains of the amylopectin molecule can be divided in A, B, and C chains. C chains constitute the backbones of the amylopectin molecules, to which B-chains are linked that at the same time carry one or more branches. The B chains are classified into B1, B2, B3 and B4 depending on their length and the number of clusters that they span.
Amylopectin