What chemical reactions are occurring during post-bottle-opening oxidation?
Exposure to air results in a loss in wine quality. This begins to be detectable within a few hours of bottle opening. This has erroneously been ascribed to the rapid synthesis of acetaldehyde. Acetaldehyde production is an indirect result of a reaction between oxygen and various phenolic compounds found in wine. The oxidation of phenolic generates hydrogen peroxide. The hydrogen peroxide subsequently reacts with a wide range of organic wine constituents. The principal reactant is ethanol, it being the principal organic constituent in wine. The reaction generates acetaldehyde and water. Acetaldehyde is well known to induce browning and, when its concentration accumulates sufficiently, masks a wines fruity character and donates an oxidized, sherry-like taint. However, acetaldehyde also rapidly reacts with sulfur dioxide and phenolic compounds in wine, producing odorless complexes. This probably explains why little volatile acetaldehyde is found in wines experimentally exposed to oxygen f
