THESIS

likely to be a significant force in both regions. Linear portions of amylopectin
constitute the crystalline regions, whereas the branch points and amylose are the main
components of the amorphous portion (Blanshard, 1987).
Figure 6 Semi-crystalline and amorphous regions in the starch granule
Source: Smith et al. (1997)
2.4 Minor components of rice starch
The main minor components in rice starch granules are lipids and protein.
Non-waxy rice starches (12.2-28.6% amylose) contain 0.9–1.3% lipids comprising
29-45% fatty acids and 48% lysophospholipids (Jane et al. 1996). Waxy rice starches
(1.0-2.3% amylose) contain ineligible amounts of lipids. Starch proteins are mostly
either storage protein or biosynthetic or degradative enzymes. Rice storage proteins
exist mainly as protein bodies (PB), PB I (prolamin) or PB II (glutelin) (Juliano,
1984). Biosynthetic enzymes are most probably entrapped within the starch granules
following starch synthesis (Glaszmann, 1987). Besides lipids and proteins,
phosphorus is an important non carbohydrate component of rice starch. In waxy rice
starches, it is mainly present as phosphate-monoesters (0.003% on dry basis), whereas
non-waxy rice starches predominantly contain phospholipids phosphorus 0.048% on
dry basis (Jane et al. 1992). Other mineral components of starch are calcium,
potassium, magnesium and sodium in their ionic form (Juliano and Viliareal, 1993).
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