Background and methodology:
This study sought to determine whether it is possible to distinguish organic wines from conventional wines on the basis of chemical composition and spectral data. The study used a total of 58 wine samples including organic and nonorganic red and white wines. The analysis included concentrations of several phenolic compounds, including trans-resveratrol, using reversed-phase high-performance liquid chromatography with both diode array and coulometric electrode array detection. In addition, total phenols, total acids, pH, and sulfur dioxide were determined for each sample. The ultraviolet-visible (UV-vis) spectra of wines were measured, and the absorbances at four different wavelengths were determined.
Findings:
The average concentrations of all compounds were calculated for organic and normal wines in all sample groups. The sulfur dioxide content was lower in organic wines than in their nonorganic counterparts except for Burgundy white wines. Interestingly, total phenol content was lower in organic white wines but higher in organic red wines, compared with corresponding nonorganic wines. The anthocyanin content was lower for organic red wines than nonorganic red wines, and the organic red wines contained significantly more trans-resveratrol. This indicates that organic viticultural techniques without synthetic pesticides increases phytoalexin (e.g. trans-resveratrol) synthesis in grapes. Phytoalexins are known to have fungicidal properties.
Reference:
Tinttunen, S., & Lehtonen, P. (2001). Distinguishing organic wines from normal wines on the basis of concentrations of phenolic compounds and spectral data. European Food Research and Technology, 212(3), 390-394.Available on-line at: http://dx.doi.org/10.1007/s002170000265