Biology Reference
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susceptibility toward enzymatic attack. Somewhat low values of digestibil-
ities from the extrusion cooked starch or starchy foods have also been seen
sometimes which may be attributed to the formation of amylose-lipid com-
plexation, starch-protein interaction, and limited water availability which
Ali, & Bhattacharya, 1997
). The decrease in the size distribution of the gran-
ule results in an increase in the surface area. As a result, process like grinding
leads to a higher percentage of hydrolysis.
Anguita et al. (2006)
observed that
extrusion provoked a decrease in particle size as compared to raw samples
and affects the digestibility. Traditional and conventional processing
methods were compared with extrusion cooking and their effects on bean
starch digestibility were studied by
Alonso et al. (2000)
. Extrusion produced
a higher increase in starch digestibility than other processing methods. Sim-
ilarly, cooking of legumes was carried out using boiling water and with
autoclaving at 121
C for up to 90 min and its effect on starch digestibility
was compared (
Rehman & Shah, 2005
). Higher digestibility values were
obtained which could be attributed the higher degree of starch gelatinization
and destruction of antinutrients, when cooked by autoclaving.
Processing of cereals such as dehulling, soaking, and germination may
result in an enhancement of digestibility due to the loss of phytic acid, tan-
nins, and polyphenols, which normally inhibits the activity of
a
-amylase and
thus decreases the starch digestibility. It has been suggested that the removal
of tannins and phytic acid creates a large space within the matrix, which
increases the susceptibility toward enzymatic attack and consequently
improves the starch digestibility
(
Rehman & Shah, 2005
). An interesting
comparison of processing parameters, such as popping, roasting, flaking,
and extrusion, and their effects on amaranth starch digestibility and predicted
GI has been reported recently in the literature (
Capriles et al., 2008
)
. The
authors reported that the starch hydrolysis rate is significantly enhanced
by popping, roasting, and flaking than extrusion. Similarly, a range of
processing types was studied and their effects on
in vitro
digestibility of finger
millet starches were reported by
Roopa and Premavalli (2008)
. The starch
digestibility has been shown to increase by 35-40% during cooking,
autoclaving, and puffing followed by pressure cooking and germination.
They also reported that baking, frying, and shallow frying reduced RDS,
while roasting and pressure cooking enhanced the RDS to about 23%
followed by cooking, autoclaving, and puffing. The increase in the sheeting
cycles of pasta dough has also been observed to enhance the
in vitro
starch
digestibility due to pulling away of protein from the starch granules (
Kim
