Biology Reference
In-Depth Information
to result in an alteration of the microstructural and rheological properties of
starch gum pastes (
Kaur et al., 2008
).
The effect of adding guar gum (at different concentrations) on the net
apparent glucose absorption has also been reported in
in vivo
studies on
growing pigs (
Ellis et al., 1995
). The pig meals containing guar gum resulted
in increased zero shear viscosity of jejuna digesta along with a significant
reduction in the rate of glucose absorption. This postprandial effect of guar
gum resulted because of gum's capacity to increase the viscosity of digesta
within the gastrointestinal tract due to the enlargement of fully hydrated
galactomannan chains. This whole phenomenon reduces the rate of diges-
tion and absorption of carbohydrates and therefore lowers the postprandial
rise in blood glucose. The presence of galactomannan in the starch mixture
impose restrictions on the swelling of starch granules during gelatinization
which results in the size reduction of starch granule remnants in the cooked
starch paste, whereas some of the granules may also not gelatinize properly
because of less availability of water molecules to starch granules (
Kaur et al.,
2008
). This incomplete gelatinization of starch granules may also increase
their resistance toward enzymatic hydrolysis. The viscous fiber derived from
different gums such as guar, tragacanth increases the viscosity even at rela-
tively low polymer concentration in the food matrix which may increase the
overall viscosity of digesta in the gastrointestinal tract. The consequence is
the decreasing of the postprandial carbohydrate absorption after ingestion of
starchy food.
Brennan, Blake, Ellis, and Schofield (1996)
studied the addition of guar
gum in white bread and studied its microstructure along with
in vitro
and
in vivo
digestibility. This was observed that the blood glucose lowering
action of gum is due to its ability to act as a physical barrier to starch digestion
along with increasing the viscosity of digesta. The association between guar
galactomannan and starch has also been confirmed through the microstruc-
tural analysis of pig digesta.
Koh et al. (2009)
studied the effect of the addition of alginate on the
in vitro
digestion of rice dough and reported a decrease in starch hydrolysis
with the addition of sodium alginate. Alginate forms a continuous net-
work by suspending the starch granules in a coherent gel which acts as
a barrier when enzymes try to access the starch. They further postulated
that starch-based alginate networks may help in the development of rice-
dough-based formulations with reduced glycemic index (GI). The pres-
ence of nonstarch polysaccharides from different plant sources may affect
the physical properties of the digesta at all sites of the gastrointestinal tract.
