THESIS

treatment (60.83 to 54.44%) and followed by the 4 to 48 hr debranched of 75 o C
preheat (61.43 to 56.09%). While, the 4 to 48 hr debranched of 95 o C preheated
treatment was the highest (69.09 to 62.63%) and classified as medium GI food.
Debranching allowed more rearrangement of linear glucans and more ordered
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structures of retrograded starches which were characterized as V-type pattern, could
be obtained as indicated by X-ray diffraction analysis. When the rice starch recrystallized
(RS III) was achieved, bigger, irregularly shaped particles with a white
spongy-like porous network and honeycomb arrangement were observed by Scanning
Electron Micrograph
(SEM).
1.3 The effect of pullulanase enzyme concentration on RS III formation,
the study found that an increasing of enzyme concentration from 8 to 14 unit/g
starches with 16 hr hydrolysis time provided the degree of hydrolysis to gradually
increase from 2.46 to 5.21% and remained stable when treated with 16 unit/g starch.
This indicated that the rice starch was completely debranched that has been attacks by
β-amylase at 96.27 and 98.82%. Degree of syneresis was dramatically lost expressible
water in the 8 to 10 unit/g starch hydrolysis and remained relatively constant in the 12
to 16 unit/g starches. In addition, enzyme concentration was affected to starch
digestibility, resistant starch content increased sharply as the amount of the enzyme
increased to 12 units/g starch, reaching highest (19.81%) resistant starch content.
Furthermore, resistant starch content in RS III samples dramatically decreased to
17.31% and 13.16% upon higher content of the enzyme (14 and 16 units/g starch).
This because of the higher degree of pullulanase hydrolysis attributed to the formation
of short linear polymers linked by α-1,4- glucosidic bonds fractions that may inhibit
rearrangement
of granules thereby preventing the starch retrogradation.
1.4 The optimum condition for larger scale production of RS III from high
amylose rice starch by enzymatically-debranching process was 15% high amylose rice
starch slurry preheated (121°C for 30 min) and debranching at 55°C for 16 hr with 12
unit/g starch of pullulanase enzyme. The optimum debranched rice starch were heated
in boiling bath for 30 min for deactivate enzyme then induced at 4°C for 16 hr.
Afterwards, the one cycle of freeze-thaw process (-10/30°C) was applied to promote