Winemaking: Conteins sulphites

I am sure that many of you wonder what means “contains sulphites” as, from some years ago, this words appear in most of the back labels of the wines you drink.

Contains sulphites

We will start by clearing up some doubts. Sulphurous anhydride, also known as sulphite, is one of the oldest food additives, already used by the Romans and the Greek.

From 2005, at the European Union, the law establishes that the wines with more than 10mg of sulphur dioxide per litter, which is to say more than 95% of the wines in the market, must bear the mention “contains sulphites” in the label.

The sulphurous anhydride, sulphur dioxide, the antioxidant E-220 or its chemical formula SO2 is essential and indispensable for the elaboration of wines due to its properties:

Antioxidant: avoids the oxidation of wines and the lost or alteration of colours or aromas.

Antioxidasic: inhibits the functioning of oxidation enzymes (tyrosinase, laccase), which come from the rotten grapes and can seriously affect the wine’s flavour and aromas.

Antimicrobial: inhibits the growth of indigenous yeasts and avoids spontaneous fermentation; it also inhibits the acetic and lactic bacteria avoiding the appearance of acetic acid and therefore preventing the wine from turning into vinegar.

On the other hand, a high concentration of sulphurous anhydride can also change the wine’s aromas and flavour and can be harmful for the consumers’ health. For this reason, the SO2 maximum doses are very much controlled. The highest are allowed in sherry (400 mg of SO2 per litter), to avoid the fermentation of residual sugars in the bottle, and in white wines and rosé wines (210 mg of SO2 per litter), since these are more fragile than red wines, regarding aromas and oxidation. Finally, in red wines, a maximum of 160 mg of SO2 per litter are allowed, since, as they have polyphenols, which are antioxidant, anthocyanins and tannins, they require a lower amount of sulphites.

To sum up, if SO2 is correctly used (it is possible to use it in lower amounts than the maximum established) low colour and low aromas wine and undesirable oxidation can be avoided and the lowest possible volatile acidity can be guaranteed, obtaining more structured wines which can be kept in the bottle for longer.

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