THESIS

value than the waxy rice flour gel. However, they found that during the first cycle the
amylose rice flour gel had changed from a smooth gel to a rough- textured porous gel
(rough surface) with a sponge-like structure that allowed it to reabsorb the separated
water. Thus, syneresis was not detectable unless this rough-textured gel pressed to
squeeze out the absorbed water. This retrogradation phenomenon occurred when the
starch gel was frozen and ice crystals spread within the gel. Upon subsequent thawing
at a lower temperature (30°C), the ice crystals melted and a rough porous gel was
formed and it was not enough to form a spongy structure and a high syneresis value
was observed. From the second to the fifth cycle, the quantity of rough-textured gel
accumulated curve indicated the formation of a rough and porous gel alter thawing
and it formation of a rough and porous gel after thawing and it confirmed the very low
freeze-thaw stability of this flour. When thawed at higher temperature (60°C, 90°C
and microwave), amylose rice flour gels no longer formed a rough, spongy gel
because of re-dissolved of retrogradation starch during heating.
5.3 The mechanisms of RS III formation during drying of the starch
The drying of recrystalized resistant starch may be performed at room
temperature or at elevated temperatures. Thus, the recrystalized retrograded starch
may be cooled from the crystal-propagating temperature to room temperature or to a
drying temperature which is above room temperature. Exemplary drying temperatures
may range from about 20°C. to about 130°C., depending on mode of drying,
preferably from about 45°C. to about 80°C., for oven-drying. Known drying methods
for the drying of starch, which do not substantially destroy or melt the crystals of
resistant starch type III, may be employed. Exemplary drying methods which may be
used include freeze-drying, oven-drying, vacuum-drying, spray drying, flash-drying,
belt-drying and drum-drying. The drying of the high-melting-point resistant starch
type III composition is conducted to achieve a shelf-stable water activity or relative
humidity of less than about 0.7. The water content of the dried product may
approximate that of commercially available flour. Exemplary moisture contents of the
dried, bulking agent or flour substitute or replacer may range from about 8% by
weight to about 14% by weightb (Relinda, 1994).
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