Oxidation is one of the major problems in winemaking including wine cellaring.

Oxidation must be prevented from harvesting, through all the steps to post-fermentation and bottling.  Instead of discussing about pH and free sulphur dioxide, the focus here is how oxidation affects wine when the closure is removed from the bottle.

At bottling wineries may use an oxygen electrode to measure the level of oxygen in the headspace (ullage).  The level of oxygen should be maintained at less than 1 per cent.  If the level of oxygen is not carefully controlled, excessive oxygen dissolves in the wine.  Once a wine is oxidised, there will be loss of aroma and flavour in wine.

How wine oxidises is a complicated subject.  There are many factors such as the concentration and types of phenols and polyphenol oxidases.   The pH and various anthocyanin, polymerisation with tannins in wine affect susceptibility to oxidation. 

Temperature influences the amount of oxygen which can be dissolved. The amount of dissolved oxygen or called aeration is greater when the temperature is low.  Oxidisation kicks in rapidly at a higher temperature.  Therefore, one of the reasons to have a cool temperature controlled storage environment is to provide a stable condition for cellaring. 

To successfully preserve wine, the correct device to use is to minimise the level of dissolved oxygen.



dissolved oxygen chart revised sept 2017.png