Universidad de Córdoba BIODISPONIBILIDAD MINERAL DE ...

Biodisponibilidad mineral de menús escolares
content in sulphydryl groups of protein system, highlighting the influence of the
content in sulphured amino acids (such as cysteine) of meat on the increase of
non heme iron bioavailability. This hypothesis seems to be confirmed when
adding N-ethylmaleimide; intake of dialysable iron diminished as N-
ethylmaleimide intake increased, because sulphydryl groups are blocked by this
inhibitor.
The importance of content in sulphured amino acids of protein has also
been demonstrated for vegetal proteins. Lombardi-Boccia et al. (1994) studied
the effect of some protein components of beans on iron dialysability, showing
that the highest mineral percentage dialyzed corresponded to globulin fraction,
which presented the highest content in cysteine dialyzed as well, instead of
albumin fraction with a higher mineral content but a lower cysteine dialyzed
content.
Caseinophosphopeptides
Contrary to meat proteins, other proteins coming from egg, milk and dairy
products impair iron absorption (Wapnir, 1990; Beard et al., 1996; Conrad,
1993;). For instance, caseins from milk inhibit iron absorption in humans. It
seems that their phosphorilated serine and threonine residues bind iron and
other minerals by ionic interactions and this iron would be released too far down
the intestine for an efficient absorption (West, 1986). Other authors point out
that a barrier effect of mucus against large peptides occur (Miller & Berner,
1989). Nevertheless, this effect can be diminished by enzymatic hydrolysis of
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