This study was undertaken to determine whether it is possible to distinguish organic wines from normal wines on the basis of chemical composition and spectral data. A total of 58 wine samples including organic and normal red and white wines from France and Germany were analysed. The concentrations of several phenolic compounds, including trans-resveratrol, were determined using reversed-phase high-performance liquid chromatography with both diode array and coulometric electrode array detection. In addition, total phenols, total acids, pH and SO2 were determined. The ultraviolet-visible (UV-vis) spectra of wines were measured, and the absorbances at four different wavelengths were determined.
The data were processed statistically using principal component analysis (PCA). Despite several different combinations of variables, separation of white wines was only achieved according to geographical origin. PCA differentiated well between organic Burgundy red wines and normal Burgundy wines. The separation was based on the concentrations of caffeic and gallic acids, total phenol content and the absorbance ratios A254/A276, A276/A320 and A320/A520. PCA was unable to differentiate organic white wines from corresponding normal wines.
The mean trans-resveratrol concentrations of 16 organic red wines and 16 normal red wines were 5.6 mg/l and 2.9 mg/l, respectively. The highest concentration, 14,5 mg/l, was found in an organic red wine from the Loire district in France.