Formation and degradation of furfuryl alcohol, 5-methylfurfuryl alcohol, vanillyl alcohol, and their ethyl ethers in barrel-aged wines

Furfural, 5-methylfurfural, and vanillin co-occurred in 64 barrel-aged red, white, and model wines with the reduction products, furfuryl alcohol, 5-methylfurfuryl alcohol, and vanillyl alcohol, and with the corresponding ethyl ethers of these alcohols. Hydrolytic studies in a model wine have shown that 5-methylfurfuryl ethyl ether is formed rapidly from 5-methylfurfuryl alcohol, but both decomposed quickly under the conditions. Vanillyl ethyl ether was also formed relatively rapidly, and both this ether and vanillyl alcohol were stable in the model wine. The formation of furfuryl ethyl ether from furfuryl alcohol and the subsequent decomposition of these two compounds were comparatively slow. The relative concentration of these aromatic alcohols and ethers in the barrel-aged wines was consistent with the observed stability of the furan derivatives, but low concentrations of vanillyl alcohol and vanillyl ethyl ether observed in all samples showed that factors other than solvolytic degradation were responsible for reducing the concentration of these compounds in wine. Furfuryl ethyl ether, which had an aroma threshold of 430 mu g/L in a white wine, was found at approximate concentrations of up to 230 mu g/L in the wines.