THESIS

morphological changes occurring at the different temperatures (Lu et al. 1996). When
the water molecules possessed sufficient kinetic energy to overcome the attractive
forces between the hydrogen-bonded starch molecules within the granule, hydration
of the grain occurred, with swelling of the amorphous regions between the crystallites.
The size of the starch granules increased slightly as the temperature was raised from
35 to 55 o C (Yeh and Li, 1996).
2.6 Rice starch retrogradation
Starch retrogradation is a process that occurs when the molecules
comprising gelatinized starch begin to re-associate in an ordered structure (Figure 8).
In the initial phases of retrogradation, two or more molecules may form a simple
juncture point, which then may develop into more extensively ordered regions.
Ultimately, under favorable conditions, crystalline order may appear and amylose
precipitation from “solution” may occur in dilute solution. Retrogradation of
gelatinized starch is a reorganization process that can involve either amylose or
amylopectin, with amylose undergoing retrogradation at a more rapid rate than
amylopectin (Jacobson et al. 1997).
Figure 9 Retrogradation during storage of cooked cereal starch paste leads to
recrystallization of the amylose and amylopectin chains
Source: Jacobson et al. (1997)
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