3.5. X-ray pattern and crystallinit

3.5. X-ray pattern and crystallinity
Rice starches exhibited the typical A-type X-ray patterns of cereal starches (Fig. 4). The intensity of five main peaks and the relative crystallinity (RC) are presented inTable 2. The numbers 1, 2, 3,
4 and 5 represent the highest peaks detected in the X-ray diffractograms (Table 2). The crystallinity of the native starches followed
the following order: low-amylose > medium-amylose > high-amylose (Table 2). The higher crystallinity of the low-amylose native
starch could be attributed to its higher amylopectin content.
The relative crystallinity decreased with an increase in the
moisture of the HMT starches, though the diffraction intensity of
the peak at 19(peak 4) of the starches increased and the highamylose starch peaks at 15,17, 17.8and 23(peaks 1, 2, 3 and
5, respectively) decreased (Fig. 4). These results suggest a decrease
in the crystalline areas due to HMT. This may explain the greater
enzymatic susceptibility evidenced by heat-moisture treated
starches.Gunaratne and Hoover (2002)also found a reduction in
the relative crystallinity in their study of potato and true yam
starches treated by HMT.