THESIS

polyhedral and irregular in shapes. The granular size was small with diameter
between 3-6 µm and form parts of compound granules. The surface of the granules
was smooth without observable pores or fissure. Piyarat (2003) reported that the
granule size mean of Thai rice starches (Supanburee 1, Jasmine rice and commercial
rice starch) showed a common size of rice starch of 4 - 6 µm.
Figure 13 Scanning electron micrographs (magnification at 2500x and 6000x) of
native commercial high amylose rice starch
1.2 Effect of preheated treatments on RS III formation
1.2.1 Degree of pullulanase hydrolysis
The reducing sugar content was used to determine the amount of
branch chains released by action of pullulanase hydrolysis on the 15% high amylose
rice starch preheated at different temperatures (75°C, 95°C and 121 o C) shown in
Figure 14 and Appendix Table E1. The degree of hydrolysis of the samples increased
with increasing incubation time and preheated temperature. The degrees of
pullulanase hydrolysis in high amylose rice starch slurry preheated at 121 o C were
significantly higher than the preheated at 75 o C and 95 o C. The degree of pullulanase
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