Oxidation

Oxidation occurs when oxygen reacts with components of a drink. This can be intended, for example in sherry or aged spirits, but is usually a fault: the colour turns darker and browner, freshness and fruit fade, and notes of nuts, apple sauce, cardboard or varnish come forward.

It is typical in wine, beer and fruit juice when they stand open too long or are stored wrongly. Protection comes from sulphur, inert gas, tight closures, cooling and darkness. For opened bottles, excluding air and cool storage help.