Analyses of trace metals, peptide ligands of trace metals and mercury speciation in home prepared bread

Abstract

Bread represents an important source of trace elements in the human diet. This study is focused on home prepared bread in the Czech Republic. The amounts of Cu, Mo, Mn, Ni and Zn (total and soluble in Tris-HCl buffer, pH 7.5), Cd, Co, Fe, Pb and Tl (total only) as well as Hg (total and soluble in mercaptoethanol-HCl mixture) in raw materials and baked bread were determined using ICP-MS. Moreover, the speciation of elements was investigated using HPLC/ICP-MS. Isolated peptide ligands of the trace elements were analysed for amino acids and characterised by MALDI-MS. The concentrations of all elements were in accordance with Czech legislation. The solubility of the Ni species was not affected by the baking process, whereas the solubilities of Mo, Mn and Zn species decreased. Soluble mercury was found only in the inorganic form. The soluble species of Cu, Mo, Mn, Ni and Zn were found in two fractions with the apparent molecular weights of 1-2 kDa and 4-5 kDa. Ligands of trace metals isolated from these fractions contained appreciable amounts of Asx, Glx, Gly, Ser and Cys. No phytochelatin-like peptides were found in the MALDI-MS spectra of isolated ligands,. Using MALDI-MS/MS, the partial amino-acids sequences of peptide ligands were obtained, and the linkages of peptides and saccharides confirmed. The MS analysis of the trypsin digest of the medium molecular weight fraction revealed several proteins rich in cysteine (e.g., barwin and amylase inhibitors).

Lebanese Population Exposure to Trace Elements via White Bread Consumption

“…Concerning the level of lead in the different brands: B2 and B3 contents were more than 2.5 fold higher than B1 (74, 203, and 260 µg/kg, respectively). The order of magnitude of B1 is in accordance with Turkish, Iranian, Ethiopian, and Spanish studies on bread [52,59] and 7 fold more higher than in data on the Czech Republic [44]. The B3 pita lead content was 32 fold higher than Lebanese data [13] which focused on Beirut.…”

“…Same as for Cd, bread is not the main source of Hg, for which it is fish and seafood, which is a concern for high fish consumers [17] and, particularly, pregnant women [15]. We found between 0.70 and 0.89 µg/kg of Hg in Lebanese pita which is by far less than in the study of Mestek and co-workers [44] who found 13 µg/kg of Hg in bread in the Czech Republic.…”

The Evaluation of Some Heavy Metals in Commonly Wheat Bread With Their Daily Intake

“…Beside the bread quality as the main diet source in developing countries, its safety needs to be confirmed and examined in terms of known toxic as trace elements. Bread is also an important and major source of heavy metals (Mestek et al, 2015), this is due to the high consumption of it. But their concentrations depend on many factors.…”