Biology Reference
In-Depth Information
The bioaccessibility of anthocyanins in
mulberry is greatly reduced after intestinal
digestion, with recovery of only 0.34%.
Anthocyanins attached to sugars make them
a high molecular weight molecule and, gen-
erally, have difficulty in being absorbed.
Thus, to be absorbed, they must be degraded
to phenolic acids. However, it is observed,
via the ability to trap free radicals, that after
digestion there is a high antioxidant cap-
acity owing to the phenolic compounds
generated from the degradation of anthocy-
anins in the intestinal medium (Liang
et al.
,
2012). In a similar study, it was found that
in vitro
gastric simulation has no major
effect on the phenolic compounds of choke-
berry juice. With a pancreatin treatment,
however, the anthocyanin had the greatest
loss (43%); flavonols and flavan-3-ols also
decreased by 26% and 19%, respectively. It
is known that dietary polyphenols are
highly sensitive to the alkaline conditions
of the small intestine and it is believed that
during digestion in the duodenum these
compounds can be transformed into differ-
ent structural forms, with different chemi-
cal properties (Bermudez-Soto
et al.
, 2007).
Wholewheat cereal has been shown to
correlate positively with reduced risk of car-
diovascular disease, diabetes and certain can-
cers. These effects are, however, due to the
effect of its fibre in the bowel microbial popu-
lations. By means of
in vitro
digestion, it was
observed that wholegrain consumption
increases the population of bifidobacteria,
and toasted grain consumption significantly
increases the growth of lactobacilli (Connolly
et al.
, 2012).
During kiwi fruit digestion
in vitro
, it
was found that the insoluble fibre decreases
slightly, whereas the soluble fibre increases
after undergoing gastric and intestinal diges-
tion. Furthermore, there was a reduction in
molecular weight and degree of methyl ester-
ification of pectic polysaccharides, which
could have an effect on the physicochemical
characteristics and could influence its func-
tionality in the large bowel (Carnachan
et al.
,
2012). In addition, the dietary fibre konjac
glucomannan (
Amophophallus konjac
),
when subjected to
in vitro
digestion, has
been shown to be resistant to degradation by
digestive enzymes (Chiu and Stewart, 2012).
Carbonated beverages and milk are high
in sugars. The food matrix in which these
sugars are found have much influence on
their bioaccessibility. When carbonated
beverages are consumed, the bioavailability
of total sugars is 55-69%, whereas for milk
it is 12-85% (Choi
et al.
, 2011).
4.4
Carbohydrates
Currently, there are various studies with
respect to starch digestibility that may vary
by such factors as the origin and composi-
tion of starch, among others. The first
enzyme involved in starch digestion is sali-
vary amylase, which occurs in the mouth as
the first stage of the digestion process. In a
short time, the bolus is transported to the
stomach. The gastric juice pH retards the
action of amylase, but increases the starch
acid hydrolysis. In the upper gastrointesti-
nal tract, lipids bound to the starch are
hydrolysed by lipases and, at this stage, an
emulsion is formed that increases the area
of oil-water interface, which allows a more
effective enzyme action (Dona
et al.
, 2010).
Likewise, studies on polysaccharides resist-
ant to digestion by the enzymes of the small
intestine show they could be delivered to
the bowel in a chemically unaltered state.
4.5
Pollutants
The main pollutants studied are metals that
may be present in food. Although one can
know the total content of contaminants in
food, the real risk is in the bioavailability of
the compound when ingested. For example,
the highest concentrations of organic mer-
cury are found in predatory fish muscles
inhabiting the waters near the bottom.
Through
in vitro
digestion, it was deter-
mined that between 26% and 62% of organic
mercury was released into the intestinal
lumen during digestion of muscle, depend-
ing on the fish species. Therefore, to declare
the potential toxicity of organic mercury
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