Oxidation in wine is a chemical process in which exposure to oxygen changes a wine’s aroma, flavour, colour and structure. Controlled oxygen exposure can be part of wine maturation and can contribute to desirable complexity in some styles. Excessive or unintended oxidation, however, can cause fresh fruit character to fade and produce nutty, bruised-apple, dried-fruit, caramel or sherry-like notes.
Oxygen reacts with compounds in wine, including phenolic substances and aroma components. The effects depend on the wine style, grape variety, acidity, phenolic content, sulphur dioxide, storage conditions and duration of exposure. White wines may darken toward gold or brown, while red wines can lose colour intensity and develop more evolved aromas.
Some wines are deliberately made or aged with controlled oxygen exposure, including certain oxidative styles from regions such as Jura and parts of Spain. In other wines, excessive oxygen exposure after opening or through poor storage can lead to loss of freshness and quality. Oxidation is not the same as microbial spoilage, although both can affect wine quality.
An opened bottle left exposed to air may become flat, dull or nutty over time. A wine showing some oxidative character may still be suitable for a particular braise or sauce, but it should not be used automatically: assess its condition and whether the flavour suits the finished dish. Cooking does not reliably correct unpleasant or faulty flavours.
Chef’s tip: Taste and smell wine before using it in a sauce. Distinguish a deliberate oxidative style from a wine that has deteriorated after opening; they can share some aromas but are not the same thing.
This term is one of hundreds covered in depth across OCS courses, learning paths, and 1-on-1 coaching with Chef Eric.
