THESIS

109
When such a starch sample is X-rayed, a crystalline V structure
is detected. The alternative for V to appear in this case would include migration
through the granule of
a large amylose molecule and/ or long chain fatty acids. A
second limiting factor would be to locate sufficient material in one place for
crystallite formation. In general, retrograded amylose gives the V-type starch X-ray
diffraction pattern. Early X-ray diffraction analysis of stretched amylose film in the
B-type structure was interpreted in terms of a six-fold single helix structure with a
repeat distance of 10.4 o A (Blackwell et al. 1969). On this basis, it could be postulated
that the mechanism of cross-linking amylose gels was via junction zones of
aggregated single
helices.
Figure
21 X-ray diffraction pattern of native HARS and RS III from 0, 16 and 48-hr
Pullulanase debranching of 75°C preheated HARS for 30 min