Retrograded waxy maize starch gels. Retrograded waxy maize
starch gels were more resistant than freshly gelatinized starch.
Digestion rates of the waxy maize starch gels depended upon
the extent of retrogradation. Indeed, the starch gel stored for
48 hr at room temperature was completely digested after 2 hr
under the experimental conditions used. It showed no significant
peaks on the X-ray diffraction pattern (Fig. 2), and it had an
onset temperature of melting (40.70 C) that was only slightly higher
than the incubation temperature of 370C (Table I). The starch
samples with increased crystallinity (X-ray diffraction, Fig. 2),
increased melting temperature and higher melting enthalpy values
(Table I) showed higher enzyme resistance. Almost complete
degradation of waxy maize starch gel stored at 60C followed
by storage at 400C for 48 hr was achieved after 3 hr, whereas
waxy maize starch gel stored at 60C followed by storage at 400C
for 29 days was not fully digested after 6 hr of incubation. This
indicates the impact of the molecular order of the starch sample
on the enzymic degradibility.