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Chromium Speciation Analysis in Bread Samples
E. Vieira , M.E. Soares and M.L.Bastos
Department of Toxicology, Faculty of Pharmacy, University of Porto, Portugal.
For several thousand years, bread has been one of the major constituents of the human diet,
making the baking of yeast leavened and sourdough breads one of the oldest biotechnological
processes. Besides the quality of bread as a nutrient, its safety is another important aspect to be
assured and can be evaluated by monitoring the putative contaminants present. These
contaminants can result from both the technological procedures and the ingredients used in the
bread fabrication, namely, the water, but mainly from the flour, the principal constituent of
bread [1]. Cereals, the raw material of bread, are important source of minerals, about 1.5-2.5%,
being phosphorus the mineral at highest concentration which is mostly associated with calcium
and magnesium phytates. Potassium levels are high in wheat, rye, barley and oats, but no cereal
grain is considered to be a high or moderate dietary source of sodium. Wheat, rye, barley and
oats are also classified as moderate sources of calcium, magnesium, iron, zinc and copper.
Wheat is also an important source of selenium and chromium. A large number of other
elements are present at trace levels [2]. Among the essential elements, chromium is a
controversial element with important essentiality and toxicity, depending on its different
species; its speciation analysis in principal human foodstuffs, as in the case of bread, is of
utmost importance.considered controversial due to its essentiality in the trivalent form, but
being genotoxic when in the hexavalent oxidation state [3]. Consequently, the analysis
speciation of this element is crucial.
In the present study it was determined the levels of total chromium and hexavalent chromium
in 76 different bread samples of both brown bread and of white bread (total of 152 samples)
obtained randomly from 20 bakeries. A method was validated, including a wet acid digestion
procedure for total chromium dissolution, a selective alkaline extraction of hexavalent
chromium and ETAAS determination
The total chromium contents were 47.3±20.0 and 50.9±22.2 µg/kg for white bread and brown
bread samples, respectively. For hexavalent chromium the values found were 5.65±5.44 and
6.82±4.88 µg/kg for white bread and brown bread samples, respectively. The hexavalent
chromium contents were, in terms of mean values, about 10% of the total chromium levels. Its
presence can be due to both contamination by contact with metallic equipments during the
technological processes of bread production and to the endogenous contents of the grains
resultant from the uptake from contaminated soils by the plants. Due to the toxic properties of
hexavalent chromium, and the capacity of transference of this species from the soils to the
plants and grains, its control in foodstuffs is of outmost importance.
References:
[1] Bratakos, M.S.; Lazos, E.S. and Bratakos, S.M. (2002), Chromium content of selected Greek foods,
The Science of Total Environment, 290, 47–58.
[2] Dewettinck, K.; Van Bockstaele, F.; Kühne, B.; Van de Walle, D.; Courtens, T.M. and Gellynck, X.
(2008), Nutritional value of bread: influence of processing, food interaction and consumer perception,
Journal of Cereal Science, 48, 243–257.
[3] Garcia, E.; Cabrera, C.; Lorenzo, M.L.; Sanchez, J. And Lopez, M.C. (2001), Daily dietary intake of
chromium in southern Spain measured with duplicate diet sampling, British Journal of Nutrition, 86,
391–396.
424 3 rd meeting of young researchers at UP