18.08.2013 Views

THESIS

THESIS

THESIS

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

In addition, the 121 o C preheated 15% rice starch slurry for 30 min<br />

was sufficient to breaking of hydrogen bonds within starch molecules that opens the<br />

granules to hydration and enzymatic hydrolysis. In the case of the 75 o C preheated<br />

15% rice starch slurry for 30 min was sufficient to swell the native rice starch<br />

granules without disrupting the granules. This permits the enzyme to access to the<br />

molecule and uniformly debranch the amylopectin molecules as can see clearly in the<br />

morphological reveal in the next section. Haralampu et al., (1998) reported that the<br />

temperatures considered appropriate for swell the starch granule without disrupting<br />

starch granule are from about 75 o C to 90 o C and the time required to sufficiently<br />

swelling the starch granules was less than 1 hour. The morphological of 15% high<br />

amylose rich starch granules changed after preheated at 75 o C and pullulanase<br />

hydrolysis for 16-hr could be clearly seen in the images shown in Figure 15.<br />

1.2.3 Morphological image of rice starch preheated-debranched<br />

Scanning electron microscopy (magnification at 2,500x and<br />

6,000x) of the 15% HARS preheated at 75°C, 95 o C and 121°C for 30 min are shown<br />

in Figure 17. There was a marked difference in shape between the 75 o C, 95 o C and<br />

121°C preheated HARS samples.<br />

The 75°C preheated of 15% annealed rice starch solution (a)<br />

exhibits swollen and partial gelatinization at the surface of the starch granules. This<br />

permits the enzyme to access to the molecule more easily and uniformly debranched<br />

the amylopectin molecules. While, the 95 o C preheated HARS show a dried surface<br />

granule without observable pores or fissure. Additionally, at 121°C preheated rice<br />

starch shown surface erosion and slightly damaged starch granules. This suggests that<br />

a considerable degree of the granular crystalline structure has been destroyed or<br />

disrupted during gelatinization at highest temperature.<br />

The difference preheated samples showed that the granular structure<br />

swelling and surface collapsed “doughnut-shaped” morphology.<br />

93

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!