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content to fish in muscle may be baseless
because the risk assessment should be based
on the bioavailability of organic mercury
(Kwasniak
et al.
, 2012). Furthermore, total
arsenic bioavailability was calculated (toxic
and nontoxic) in different fish and shellfish
samples through
in vitro
simulation of gas-
trointestinal digestion, where there has been
observed a high bioaccessibility (85-100%);
moreover, it was observed that fish and
shellfish with higher fat content have a
lower arsenic bioaccessibility (Moreda-
Pineiro
et al.
, 2012).
For other pollutants, fat oxidation prod-
ucts have been studied, which can produce
toxic compounds such as the aldehydes a,
b-unsaturated oxygenates (OabUAs), espe-
cially by the oxidation of omega-6 and
omega-3 acyl groups. Subjecting oils rich in
these fatty acids to thermal treatment pro-
duces OabUAs, which remain unchanged,
being bioaccessible in the gastrointestinal
tract and thereby able to reach the circula-
tory system (Goicoechea
et al.
, 2011).
In one study, using
in vitro
digestion deter-
mined that the formation or release of BCM7
is promoted primarily by the action of gas-
trointestinal proteases, independent of the
milk product (De Noni and Cattaneo, 2010).
Coenzyme Q10 is a fat-soluble vitamin
that plays an important role in the process of
cellular breathing and energy production,
and is also an important antioxidant.
Coenzyme Q10 is absorbed in the small intes-
tine. Meat, especially liver and heart, is an
important source of coenzyme Q10, because
of its high content in cooked meat and owing
to its digestibility, which reaches up to 68%
of bioaccessibility (Ercan and El, 2011).
Selenium (Se) is an essential trace ele-
ment that plays an important role in the
activity of enzymes involved in antioxidant
protection and thyroid hormone metabo-
lism. By consuming selenized yeast by an
in
vitro
digestion it was found that selenome-
thionine (SeMet) was the main compound
identified in the gastrointestinal extract.
The results showed that 89% of total Se was
extracted after gastrointestinal digestion,
but only 34% was quantified as free Se
(Reyes
et al.
, 2006).
Wheat grass is consumed as a food sup-
plement in tablets because it contains essen-
tial elements such as K, Mn, Zn, Fe and Na.
The bioaccessibility of these minerals was
calculated through an
in vitro
gastric diges-
tion, where 39-60% of bioaccessibility was
obtained from the fresh wheat grass, whereas
bioaccessibility was 17-43% in wheat grass
tablets, indicating that the fresh wheat grass
is an effective source of minerals (Kulkarni
et al.
, 2007).
4.6
Others
Flaxseed is a good source of soluble fibre
and lignans, particularly the lignan secoiso-
lariciresinol diglucoside (SDG), which can
be metabolized by bowel microflora in its
aglycone secoisolariciresinol (SECO) and
lignans enterodiol (ED) and enterolactone
(EL), resulting in health benefits through
their antioxidant and phytoestrogenic activ-
ity. By simulating
in vitro
the entire diges-
tive process, we determined that SDG was
released in the large intestine and SECO
was released by microbial action in the
ascending colon, which then becomes lig-
nans ED and EL forward from the transverse
bowel (Eeckhaut
et al.
, 2008).
Milk-derived peptide bioactivity has
been extensively studied, and opioid activ-
ity, decreased blood pressure, antimicrobial
activity and immunomodulators have been
reported. b-Casomorphin-7 (BCM7) is an
exogenous opioid peptide derived from
proteolysis of the b-casein, which was iso-
lated from an enzymatic digestion of casein.
4.7
Bioavailability
Bioavailability studies in humans have
shown that many of the polyphenolic com-
pounds vary in their absorption depending
on the compound and/or food matrix.
Moreover, the bioavailability of polyphe-
nols may be diminished by a high biliary
and intestinal secretion of their conjugates.
Therefore, the volume of dietary polyphe-
nols and their conjugates must remain in
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