Always present in wines, this is a substance that performs various functions, carrying out:
- antioxidant action (preventing contact with oxygen)
- antioxidasic action (inhibition of tyrosinase and laccases)
- antiseptic action (inhibition or slowing-down of the development of yeasts and bacteria)
- extracting action (increase in the extraction of phenolic substances from the skins of the grapes)
- action on the wine’s taste characteristics, in that it maintains the wine in a state of reduction, thus reducing tired sensations and increasing its freshness.
Sulfur dioxide is used at various times: from the maintenance of winemaking vessels to the treatment of the grapes, from its use in the must to that in the wine.
Free sulfur dioxide is that which has not combined with the other substances in the wine: for this reason it is particularly noticeable on the nose and on the palate, especially if it is present in doses of more than 20-25 mg/l. Even if the law permits, at the time of release to consumers, a maximum dose of 160 mg/l for red wines and 200 mg/l for whites and rosés, it is important that the total sulfur dioxide should not be more than 100-120 mg/l for white wines, although one can accept very slightly higher values for sweet wines (anti-fermentative function).
Sensory effects
In very limited doses, it reinforces the aromatic and gustatory sensations; if excessive, it generates acrid, pungent sensations (wax matches, sulfur), which become unpleasantly sharp and bitter in the mouth. It is often the main cause of the classic headache.
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