Amylopectin is a key component in the crystallization of starch’s final configuration, accounting for 70-80% of the final mass. Composed of α-glucose, it is formed in plants as a primary measure of energy storage in tandem with this structural metric.
Amylopectin bears a straight/linear chain along with a number of side chains which may be branched further. Glucose units are linked in a linear way with α(1→4) Glycosidic bonds. Branching usually occurs at intervals of 25 residues. At the places of origin of a side chain, the branching that takes place bears an α(1→6) glycosidic bond, resulting in a soluble molecule that can be quickly degraded as it has many end points onto which enzymes can attach. Wolform and Thompson (1956) have also reported α(1→3)linkages in case of Amylopectin. Amylopectin contains a larger number of Glucose units (2000 to 200,000) as compared to Amylose containing 200 to 1000 α-Glucose units. In contrast, amylose contains very few α(1→6) bonds, or even none at all. This causes amylose to be hydrolyzed more slowly, but also creates higher density and insolubility.
Amylopectin is divided into A and B helical chains of α-glucose. A chains are chains that carry no other chains, resulting in an eventual terminus, whereas B chains are chains that do carry other chains, perpetuating the amylopectin polymer. The ratio between these is usually between 0.8 to 1.4.
The formation of chain structures has a direct impact on the overall strength of the polymeric whole; the longer a chain is, the more differing the effects amylopectin will have on starch’s morphology. Packing of chains, inter block chain length (IB-CL), also has been correlated to have a direct positive impact on the gelatinization temperature of starch granules. In tandem, the IB-CL will increase as the length of B chains increases, meaning that as the length of individual B chains increases, as does the blocks between connections with other chains. Finally, in general, the more densely packed the resulting molecule of amylopectin, the higher the strength of the starch gel as a whole unit.
Starch utilizes the density-strength correlation of amylopectin as a measure of forming dense, strong bricks as a basis for the final starch configuration. Amylopectin in starch is formed into helices to compose hexagonal structures that will subsequently be differentiated into A (cereal) and B (high-amylose; tubular) type starch. Structurally, A is more compact, while B is looser, hence the higher concentration of amylose.