By using Electron Spin Resonance (ESR) spectroscopy, we have detected
free radicals in red wine, whether fermented on oak or not, and in whi
te wine only when it has been fermented on oak. These radicals would a
ppear to be associated with the phenolics, because the ESR signal from
the residue of red wine treated with polyvinyl polypyrrolidone is red
uced by similar to 80%. Any inhibition of lipid oxidation by red wine
phenolics in vitro will take place in the presence of these radicals,
which have a linewidth of 2.0 +/- 0.1 gauss and a g-value of 2.0038 +/
- 0.0001.