PRINT THIS PAGEMeunier, Michel. (2004, August). Hyperoxidation: A technique to enhance white wine stability. The Australian and New Zealand Grapegrower & Winemaker, pp. 87-89.
Phenolic compounds contribute to the colour and astringency of white wines. These compounds are divided into two groups the non flavonoids and the flavonoids. The flavonoids are derived from the skins, seeds and grape bunches and are primarily responsible for the development of bitterness, astringency, browning and aroma alterations during oxidative ageing of white wines. Increased skin contact leads to elevated levels of flavonoid phenolics.
Hyper oxidation is one technique that can be used to reduce the levels of these compounds. Hyper oxidation is the deliberate oxidation of the crushed grapes or juice.
Typically oxygen is injected into the juice at around 9 mg per litre of molecular oxygen per litre of juice. This leads to rapid oxidation of the more oxidisable phenolic compounds. These oxidised compounds settle out and the juice is racked prior to the primary yeast fermentation.
Advantages of hyper oxidation:
- Allows polymerisation and subsequent precipitation of phenolic compounds that may contribute to bitterness.
- Produces enzymatic browning in juice that is reversed during the reductive fermentation process.
- Decreases levels of p-coumaric acid, a non flavonoid in wine.
- Generates more aromatic wines with more finesse than those produced where steps have been taken to protect against oxidation.
Juices with levels of flavonoids > 100 mg per litre may require higher levels of oxygen to be added. Close monitoring of the oxygen conditions should be carried out. Excess oxygen addition can lead to a loss of aroma in the resulting wine.
Contains references to other papers.