Meanwhile, high temperature at filling stage could also increase the amount of long B chains of amylopectin
and decrease short B chains (Asaoka et al., 1985), which is more dominantly attributable to the changing activities of soluble starch synthase (SSS), starch branching enzyme (SBE) and starch debranching enzyme (DBE) in filling endosperms, rather than the limitation in sucrose supply from photosynthesis tissues and its cleavage metabolism in non-photosynthesis tissues.
However, due to the fact that the diets were isoproteic, isolipidic and isocaloric, the differences in the digestibility observed in the present study can be explained by the differences in the molecular structure between amylose and amylopectin
. Amylose, having an essentially linear and packed chain, is more compact in the granule, which makes the access of digestive enzymes difficult; on the contrary, the amylopectin
molecule, having a branched chain, allows greater access of these enzymes.
It indicates that amylopectin
degradation enabled biological decomposition of starch.
Differences in starch degradability have been seen in varieties that contain different levels of amylase to amylopectin
. High levels of amylase results in more extensive hydrogen bonding, and a subsequent increased resistance to hydrolytic enzymes.
Relationship between the distribution of the chain length of amylopectin
and the crystalline structure of starch granules.
Scientists suspect that boosting the amount of amylopectin
in starch may concurrently reduce the amount of amylose, resulting in a value-added, low-amylose flour.
The enthalpy--the measure of the total energy of a thermodynamic system--of retrograded amylopectin
in the parboiled rice ranged from 1.39 to 3.10 J per gram for samples that were immediately dried after processing.
In all cases, starch is submitted into the extruder to high temperatures and mechanical stresses which modify its basic structure: the chains of amylose and amylopectin
are broken, the molecular weight is reduced and thus the viscosity of the molten product is lowered.
* RS4: starches that have been chemically modified (e.g., dextrinized amylopectin
or cross-linked amylase) in a way that protects them from attack by amylase enzymes.
'But if you add a sufficient number of brown rice samples, then rice color won't confuse readings on other unrelated characteristics, such as amylopectin
The polar components interact with the surface of amylopectin
molecules, in doing so, the non-polar fatty acid chains provide a degree of 'waterproofing'.
The amylose and amylopectin
ratio of starch governs its physical properties.