Amylopektin

Amylopectin is a highly branched glucose polymer that forms a major fraction of starch, the plant storage carbohydrate. It is the branched component that, together with amylose, constitutes the common starch found in seeds, tubers, and other plant tissues.

The molecule consists of a backbone of α-1,4-linked glucose units with numerous α-1,6 branches, creating a tree-like structure. Branch points occur at irregular intervals, typically every 24–30 glucose residues, resulting in a high molecular weight and a dense, semi-crystalline arrangement within starch granules.

In most starches amylopectin accounts for about 70–80% of the starch by weight, with amylose making up the remainder. The branched architecture of amylopectin contributes to the granule’s crystallinity and greatly influences its gelatinization, swelling, and paste viscosity. Its presence also affects how starch behaves during heating and cooling, including gel formation and textural properties in foods.

Biosynthesis in plant plastids involves starch synthases and branching enzymes. Amylose is synthesized mainly by granule-bound starch synthase, while amylopectin structure is shaped by starch branching enzymes and other synthases that create the characteristic branched network within the granules.

Digestive and nutritional aspects vary with amylose–amylopectin composition. Amylopectin is generally digested more rapidly by human amylases, contributing to higher glycemic responses, whereas amylose-rich fractions can form resistant starch under certain conditions.

Industrially, amylopectin-rich starches are valued for thickening, gelling, and texture properties in food and non-food applications. Common sources include corn, potato, and wheat starches. Analytical methods frequently involve debranching followed by chain-length analysis to quantify amylopectin content.