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Concept
Amylopectin
Summary
Amylopectin ˌæmᵻloʊˈpɛktᵻn is a water-insoluble polysaccharide and highly branched polymer of α-glucose units found in plants. It is one of the two components of starch, the other being amylose.
Plants store starch within specialized organelles called amyloplasts. To generate energy, the plant hydrolyzes the starch, releasing the glucose subunits. Humans and other animals that eat plant foods also use amylase, an enzyme that assists in breaking down amylopectin, to initiate the hydrolyzation of starch.
Starch is made of about 70–80% amylopectin by weight, though it varies depending on the source. For example, it ranges from lower percent content in long-grain rice, amylomaize, and russet potatoes to 100% in glutinous rice, waxy potato starch, and waxy corn. Amylopectin is highly branched, being formed of 2,000 to 200,000 glucose units. Its inner chains are formed of 20–24 glucose subunits.
Dissolved amylopectin starch has a lower tendency of retrogradation (a partial recrystallization after cooking—a part of the staling process) during storage and cooling. For this main reason, the waxy starches are used in different applications mainly as a thickening agent or stabilizer.
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.
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Related concepts (17)
Amylopectin
Amylopectin ˌæmᵻloʊˈpɛktᵻn is a water-insoluble polysaccharide and highly branched polymer of α-glucose units found in plants. It is one of the two components of starch, the other being amylose. Plants store starch within specialized organelles called amyloplasts. To generate energy, the plant hydrolyzes the starch, releasing the glucose subunits. Humans and other animals that eat plant foods also use amylase, an enzyme that assists in breaking down amylopectin, to initiate the hydrolyzation of starch.
Waxy potato starch
Waxy potato starch is a variety of commercially available starch composed almost entirely of amylopectin molecules, extracted from new potato varieties. Standard starch extracted from traditional potato varieties contains both amylose and amylopectin. Waxy potato starch, when gelatinized, has a clearer film, a stickier paste and retrogradates (thickening of starch film or paste during storage) less compared to regular potato starch. Waxy potato starch derivatives are used in textile sizing and food applications.
Amylose
Amylose is a polysaccharide made of α-D-glucose units, bonded to each other through α(1→4) glycosidic bonds. It is one of the two components of starch, making up approximately 20–30%. Because of its tightly packed helical structure, amylose is more resistant to digestion than other starch molecules and is therefore an important form of resistant starch. Amylose is made up of α(1→4) bound glucose molecules. The carbon atoms on glucose are numbered, starting at the aldehyde (C=O) carbon, so, in amylose, the 1-carbon on one glucose molecule is linked to the 4-carbon on the next glucose molecule (α(1→4) bonds).
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