THESIS

Figure 4 Cluster model of amylopectin. ((= Reducing chain-end). Solid lines
indicate (1,4)- α-D- glucan chain; arrows indicate α-(1,6) linkage.
Source: Lineback (1993)
Each amylopectin molecule contains up to two million glucose
residues in a compact structure with hydrodynamic radius 21-75 nm (Lineback, 1993).
The molecules are oriented radically in the starch granule and as the radius increases
so does the number of branches required filling up the space, with the consequent
formation of concentric regions of alternating amorphous and crystalline structure
(Figure 5). The structural properties of amylopectin, with amylose, vary depending on
source (Table 3). Rice amylopectin have ((-amylolysis limits of 56 – 58%, chain
lengths of 18-21, and widely different DP and linear chain distribution values
(Hizukuri et al. 1989 and Takeda et al. 1987). Low average DP values are observed
for indica rice (4,700), as compared to those for japonica rice (12,800) and waxy rice
(18,500) amylopectin.
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