Aged Red Wines Research Articles

Formation of Reduced Pressure in Barrels During Wine Aging

During the past few years, various cellar workers have noticed intermittent evidence of vacuum inside oak barrels during aging of wines under warehouse conditions (4,7). This occurred only with barrels which were not topped, and was especially noticeable in barrels that had been undisturbed for many months or years. This experiment sought to determine the nature and extent of any vacuum which forms under cellar conditions during undisturbed barrel aging of red table wines.

The polymeric nature of wine pigments

During conservation and ageing of red wines, the grape anthocyanins initially responsible for wine colour are displaced, progressively and irreversibly, by more stable polymeric pigments, which account for up to 50 per cent of colour density within the first year. These new pigment forms are much less sensitive to changes in pH than are the anthocyanins, and are quite resistant to decolorization by sulphur dioxide. Evidence is given in support of the hypothesis that the polymers contain quinonoid anhydrobase chromophores derived from the anthocyanins, and which have been stabilized by substitution with reactive flavans. Some possible structures of these tannin pigment materials are discussed.