Ascorbic Acid
Some winemakers use ascorbic acid, or vitamin C, as an antioxidant. Ascorbic acid sometimes protects the fruit and acts as an antioxidant, while at other times it can act as a proto-oxidant, or oxidative promoter. Recognised by the OIV, ascorbic acid is permitted for use in grape wine in over 65 countries worldwide.
Ascorbic acid is the enolic form of 3-oxo-L-gulofuranolactone (2,3- didehydro-L-threohexano-4-lactone). This product falls into the category of antioxidants and is used as a reducing agent used to prevent oxidation. Its use is subject to statutory regulations regarding limits. Odorless white or very pale yellow crystalline powder with an acidic flavor. Aqueous solutions rapidly decay in air and light and have a maximum stability at pH 5.4. Melting point in a capillary tube: approximately 190 °C with decomposition. Ascorbic acid in aqueous solution has a pH of less than or equal to 3.
For further substance information, please see the International Oenological Codex.
Synonyms: Vitamin C
CAS Number: 50-81-7
E Number: 300
INS Number: 300
International Organisations
Codex Alimentarius
–Classification, Food Category, Functional Class, and Recommended Usage are not available at this time.
International Organisation of Vine and Wine (OIV)
-Food Category Wine (grape) Functional Class Antioxidant Ascorbic acid: additive Recommended Usage (International Code of Oenological Practices – Annex: Maximum Acceptable Limits) Amount used in the treatment: 250 mg/l Residue in the wine: 300 mg/l
FIVS
Classification Category 2 – Naturally occurring in grapes and treatment residual in wine
Recommended Usage
Good Manufacturing Practice (GMP)
As outlined in the OIV’s International Code of Oenological Practices, Ascorbic acid is used:
As the enolic form of 3-oxo-L-gulofuranolactone (2,3- didehydro-L-threohexano-4-lactone). This product falls into the category of antioxidants and is used as a reducing agent used to prevent oxidation. Its use is subject to statutory regulations regarding limits.
Usage in Winemaking:
Ascorbic acid (or vitamin C) has been used in the wine industry as an antioxidant due to its ability to rapidly remove molecular oxygen (O2) from juice or wine. This reaction between ascorbic acid and O2 takes place almost 1,700 times more rapidly than that between sulphur dioxide (SO2) and O2. SO2 does not react directly with O2, but instead it reacts mainly with hydrogen peroxide (H2O2), which is formed through the oxidation of a phenolic component. In the presence of laccase, ascorbic acid is a substrate that will yield O2 consumption without peroxide formation.
Winemakers add ascorbic acid when wines contain disulfide for the following reasons:
- Smaller quantities of disulfide give wines a rubber or garlic smell.
- When very small quantities are present, disulfide can give wine a vague, dirty odour.
- At even lower levels, disulfide may not produce a specific odour.
- Minute quantities of disulfide are sometimes not detectable but can kill the normal bouquet of a fine wine.
- When ascorbic acid is added to wine, the reaction between ascorbic acid and disulfide converts the disulfide into a material called mercaptan. Once converted completely into mercaptan, the addition of copper sulfate in very small quantity (0.05 to 0.5 milligrams per liter) removes the mercaptan from the wine. This treatment is only effective when ascorbic acid is added to the wine several days before the copper sulfate addition.
See FIVS technical papers for more information - click here.
