3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
M a n g a n e s e F r a c t i o n a t i o n P r o f i l e s
Fig. 1 shows the chromatographic profiles of 55 Mn in the
studied samples. The typical molecular mass distribution pattern
of this element is the presence of only one highly abundant
fraction between 2,126–7,000 Da. This fact indicates
that manganese in wines is mainly associated with polysaccharides,
peptides, proanthocyanidins or low molecular mass
proteins. Condensed tannins and anthocyanins are the most
important metal ligands, since these species have numerous
coordination sites capable of binding metal cations. In addition,
the molecular mass indicates that the organic compound
is not an anthocyanin. It has been reported that cyanidin-3-
O-glucoside anthocyanin with two – OH groups in the ortho
position can complex Mn at the ratio 2 : 1 ref. 4 , but the chromatograms
shows the absence of Mn in the retention time of
this anthocyanin or the abundance is too low.
Fig. 1. Molecular mass distribution of manganese species in
wines
Lead Fractionation Profiles
Fig. 2. shows the superimposed chromatographic profiles
of 208 Pb in wines. Lead is mainly bound with high
molecular mass compounds as can be concluded from the
co-elution with Metallothionein I (7,000 Da). All the samples
present around the same abundance of this Pb-containg
fraction. It is remarkable the presence of two peaks in this
molecular mass region in sample 5. Sample 10 is the only
one that presents a Pb-containing fraction of about 2,126 Da.
In several samples 1,4,11,17,18 , a low abundant fraction with
a molecular mass from 1,325 to 2,126 Da, have also been
detected. Experiments with untreated wine passed through
a minicolumn packed with polyurethane foam modified by
2-(2-benzothiazo-lylazo)-p-cresol indicated that Pb(II) is
strongly associated to other constituents, possibly bound with
pectic polysaccharides and/or other related high-molecular-
s637
Fig. 2. Molecular mass distribution of lead species in wines
weight natural organic species 14 . As previously reported 6 ,
lead in wine can be bound with a structurally complex pectic
polysaccharide (rhamnogalacturonan II-RG II) that present
the ability to form dimmers cross-linked by 1 : 2 borate diol
esters (dRG II). RG-II is a major polysaccharide of wine and
is mainly present as a dimmer, although the monomeric form
can also be detected. The molecular mass of dRG II is about
10 kDa, so the presence of B and Pb in this region is a marker
of the presence of the complex. For this reason 11B was
monitored together with 208 Pb and they were detected in all
the samples in the fraction of about 7,000 Da. Fig. 3 shows
the presence of both elements in the most abundant fraction
of lead in wines (about 7,000 Da) in sample 1.
Fig. 3. Coelution of Pb and b in sample 1
A r s e n i c F r a c t i o n a t i o n P r o f i l e s
The molecular mass fractionation profiles of arsenic
(Fig. 4.) are very different to those previously considered for
other elements. Although the abundance of As-containing
peaks is low and not all the samples present this element
above the detection limits, we can find that arsenic is present
in two fractions, one of low molecular mass (526–1,355 Da)
and other of about 2,126 Da. It has been reported (15) that
the inorganic arsenic, As (III) (arsenite) is the major arsenic
specie in wines but the organic species such as dimethylarsinic
acid (DMAA) and monomethylarsonic acid (MMAA),
are under the detection limits of hidride generation-atomic
spectroscopy fluorescence (HG-AFS). Other papers report
that, in most of wines, DMAA is the most abundant specie,
but the total inorganic aresenic fraction is considerable 16 .
Some arsenosugars have also been determined in wines with
a molecular mass from 326 to 478 Da 17 . However, the association
of As in wines with an organic compound of high
molecular mass (2,126 Da) have not been reported until
now.