Oxidation
Too much contact with oxygen oxidizes wine. This happens when air permeates the seal of a bottle. A small amount of oxygen allows a wine to age slowly, but too much oxygen can have a bad effect on the quality of the wine.

The three main causes of oxidation are:
• A faulty cork
Each cork differs in its ability to restrict air permeation since a cork is a natural closure.

• A dry cork
A bottle of wine stored upright for an extended period can cause a cork to lose moisture and this leads to increased air in the bottle.

• Over ageing
If a wine is allowed to age beyond its lifespan, it will show oxidation characters. One sign of this is the colour of wine. White wines will have a brassy hue and red wines an amber one. The aroma of oxidized wine is dull and flat. Its palate is full in flavour and can be both sharp and bitter.

The use of alternative closures, such as screw caps and synthetic closures, prevent the incidences of cork-derived taint and reduce the incidence of oxidation.