Biology Reference
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be complete within the first few hours, while amylopectin aggregation and
crystallization occur at later stages during refrigerated storage (
Singh,
McCarthy, et al., 2008
). The linear chains of amylose facilitate the cross-
linkages through hydrogen bonds, whereas the branched amylopectin delays
its recrystallization. The retrogradation properties of starches are also
influenced by the structural arrangement of starch chains within the amor-
phous and crystalline regions of the ungelatinized granule, because this struc-
tural arrangement influences the extent of granule breakdown during
gelatinization and also influences the interactions that occur between starch
chains during storage (
Singh, Kaur, & Singh, 2004
). RS formation in the
cooked starches stored at refrigeration temperatures is greatly influenced
by the extent of retrogradation. Retrograded amylose from peas, wheat,
and potatoes is highly resistant toward enzymatic hydrolysis. It has been
observed that storing cooked rice at refrigerated temperatures may lead to
a reduction in their digestibility and estimated GI
(
Frei, Siddhuraju, &
Becker, 2003; Hu, Zhaoa, Duana, Linlina, & Wu, 2004
)
. The same phe-
nomenon can be observed in cooked starchy tubers. Potatoes were cooked
and then cooled at refrigeration temperatures for up to two days and their
starch digestibilities were compared with the freshly cooked ones by
Mishra,
Monro, and Hedderley (2008)
. They reported that percentage of RDS in
the refrigerated potatoes decreased to 45% from 95% of the freshly cooked
potatoes which could be attributed to the retrogradation of starch and RS
formation. The dispersed polymers of the gelatinized starch during refriger-
ated storage have been observed to undergo retrogradation which leads to
the formation of
to semicrystalline structures
that resist digestion by
amylases.
6. CONCLUSIONS
Starch is the commonest storage carbohydrate in plants and also the
largest source of carbohydrates in the human food. Starches can be classified
according to their digestibility as rapidly digestible, slowly digestible, and
RS. The microstructure of food, whether natural or created during
processing/storage, plays an important role during digestion of starch in
the gastrointestinal tract. The rheological characteristics of foods, either nat-
ural or achieved through added ingredients, may influence the digestion of
starch by affecting the availability of water. The other constituents of food,
such as proteins, lipids, polysaccharides, and added ingredients, play a signif-
icant role during processing and thus contribute to the creation of a typical
