Ascorbic acid

The natural form of ascorbic acid, vitamin C, is present in varying quantities in plants, including grapes. A powerful antioxidant, this acid is also used in its synthetic form in oenology to prevent oxidation of the wine and preserve its colour and aromas.

Vitamin C is good for wine, but it's also good for our health!

Although it is the most fragile of the vitamins, vitamin C has many benefits for the body:

  • It protects blood vessel walls,
  • It facilitates the assimilation of iron,
  • It captures free radicals and therefore prevents the oxidation of body tissues,
  • It helps defend the body against bacterial and viral infections,
  • It helps healing.
This vitamin is found in many plant-based foods, such as fruit and vegetables... including grapes! Its natural ascorbic acid content is around 4 mg per 100 g of fresh fruit. The concentration of vitamin C in the must will be around 50 mg/l. However, this quantity is often insufficient to prevent oxidation of the wine, which is why synthetic ascorbic acid, E300, is used in viticulture and winemaking..

The role of ascorbic acid in oenology

Although the presence of oxygen is essential at some stages in the winemaking process, too much O2 in the must or wine is harmful. . The result is oxidation of various oenological constituents, with this degradation altering the aroma, bouquet and freshness perceived on tasting. The use of E300, which is water-soluble and marketed in the form of a translucent crystalline powder, makes it possible to fix the oxygen dissolved in the wine. It thus helps the winemaker to combat moderate and temporary oxidation in order to preserve the organoleptic properties of the finished product and improve its conservation.

Ascorbic acid is added to the must to :

  • prevent oxidation,
  • stabilise the ferric salts, which then do not oxidise, thus protecting the wines from iron breakage,
  • reduce sulphiting (addition of sulphur or sulphites, SO2).
Added immediately to the wine, it prevents :
  • premature ageing of red wines,
  • pinking (oxidative pinking) in white and rosé wines,
  • atypical ageing of wines (UTA),
  • oxidative shocks during bottling,
  • responsible for "bottle disease".

Regulations governing the addition of E300 to wine and precautions for use

Authorisation for the use of ascorbic acid for oenological purposes dates back to 1962, and sets the maximum dose at 250 mg/l.. Its use is permitted in organic farming and it is therefore present in some organic wines, but is prohibited in biodynamic and natural wines. The usual dosage of this additive is:

  • 2 to 10 g/100 kg on the grapes,
  • 5 to 10 g/hl for red wines,
  • 10 à 15 g/hl for rosé and hite wines.
Winemakers must take specific precautions to ensure the effectiveness of ascorbic acid. It should be diluted in ten times its weight of wine or must, then used without delay, as vitamin C is fragile and deteriorates on contact with air. But above all, it is essential to add it with sulphur. Sulphur eliminates hydrogen peroxide, a powerful oxidant produced by the reaction between ascorbic acid and oxygen.