Presentado en Book of abstracts of the11th International Conference on Electroanalysis ESEAC, 2006; P2-081. Three year old samples of Vitis vinifera origin-controlled red wine samples were spiked with adequate amounts of metals and subsequent colorimetric parameters evolution and complexing capacity behaviour were checked.
The used approach consisted in the study of the complexing capacity of natural occurring ligands on wine with respect to Zn and Cu by means of stripping voltammetry in acetate pH 4 buffered 1:5 diluted samples onto which increasing amounts of standard metals were added. The resulting titration curves allowed the ligand concentration to be estimated, and the Scatchard and/or Langmuir algorithm transformation permitted the elucidation of the predominant stoichiometries of existing complexes. This technique has proved very sensitive to detect changes in the composition of samples along fermentation time as a function of major ligand populations .
Samples treated in exactly the same way were subjected to spectrometric analysis at selected wavelengths. Stability of polyphenol-metal complexes and its possible redistribution on increasing metal concentration can be followed-up by both classical and Cielab space colorimetric parameters. We have already observed that Fe addition modified certain colorimetric parameters reflecting a change in the polyphenol-metal complexes nature .