Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1410646 | Journal of Molecular Structure | 2008 | 4 Pages |
Abstract
The thermodynamics of the molecular association process between malvidin-3-O-glucoside and ellagic acid (so-called “copigmentation”) was studied in model wine solutions in the presence and absence, respectively, of ferrous and ferric ions. The Gibbs free energy, enthalpy, and entropy values of the complexation process were determined by means of a spectrofluorometric method. A combination of the Job's method with the van't Hoff theory was used for data evaluation. The results show the generally exothermic character of the process. The free enthalpy changes obtained during formation of malvidin-3-O-glucoside-ellagic acid complexes increase from â17.8Â kJ/mol to â40.5Â kJ/mol in the presence of Fe(II) ions. The increased free enthalpy is a consequence of the drastic reduction of entropy change due to the slight “swinging” movement of the interacting malvidin and ellagic acid molecules in the complexes stabilized by the ferrous ions. These results are also supported by the findings of other authors stating that iron ions play an important role in the stabilization of color in the plant kingdom and various plant products.
Related Topics
Physical Sciences and Engineering
Chemistry
Organic Chemistry
Authors
Sándor Kunsági-Máté, Erika Ortmann, László Kollár, Kornélia Szabó, Martin Pour Nikfardjam,