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Why does wine change over time? Even the most brilliant research chemist cannot give a full answer to this question. Pasteur's work in the 19th century showed that oxidation affects wine exposed to air. Oxidation slowly (sometimes quickly) destroys the colour in a wine, turning both red and white wines brown. A cut banana, or apple, suffers the same fate. But Pasteur's hypothesis that this process takes place in a corked bottle seems incorrect. Not enough air passes through the cork to allow oxidation. What is going on is a process of reduction: the small amount of oxygen present in the wine is fuelling various chemical reactions, which themselves involve bacteria, enzymes and other components of the wine. Wine is a complex chemical: over 400 individual components have been identified in it. |
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