Free radicals in red wine, but not in white?

By using Electron Spin Resonance (ESR) spectroscopy, we have detected free radicals in red wine, whether fermented on oak or not, and in white wine only when it has been fermented on oak. These radicals would appear to be associated with the phenolics, because the ESR signal from the residue of red wine treated with polyvinyl polypyrrolidone is reduced by approximately 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.