1, antioxidation: Sulfur dioxide can prevent the oxidation of wine, especially hinder and destroy polyphenol oxidase in grapes, including tyrosinase in grapes and insect laccase in moldy grapes, and reduce the oxidation of tannins and pigments.
2. Clarification: Adding appropriate amount of sulfur dioxide delayed the start of fermentation, which was beneficial to the precipitation of suspended substances in grape juice and made grape juice clarify quickly.
3. Dissolution: Due to the application of sulfur dioxide, the generated sulfurous acid is beneficial to the dissolution of pigments, tartar, inorganic salts and other components in the peel, which can increase the content of extract and the chromaticity of wine.
4. Acidification: Acidification is the result of sterilization and dissolution.
Service time of sulfur dioxide:
Sulfur dioxide in wine plays an important role, so pay attention to their use time. Only when sulfur dioxide is used at the right time can the best effect be achieved.
1, before fermentation: 30 ~ 80 mg/l.
Sulfur dioxide treatment should be carried out before fermentation. However, as for the raw materials for brewing red wine, it should be done immediately after the grapes are broken, pedicled and pumped into the fermentor, and sulfur dioxide should be added when canning. After canning, pour the can once to make the added sulfur dioxide and fermentation substrate mix evenly.
Raw materials cannot be treated with sulfur dioxide before crushing or when crushing and removing stems. If treated with sulfur dioxide, sulfur dioxide can't be mixed evenly with raw materials. Part of sulfur dioxide is lost due to the volatilization and fixation of solid part, which can not protect fermentation substrate. Sulfur dioxide gas may react with metal equipment, and if it is treated during crushing and stem removal, it may corrode metal equipment.
When brewing white wine, sulfur dioxide treatment is carried out immediately after juicing to protect grape juice from oxidation before fermentation. Avoid sulfur dioxide treatment after crushing and removing stems and before separating grape juice from skin residue, so as to avoid part of sulfur dioxide being fixed by skin residue, thus reducing the effect of protecting grape juice; The dissolution of sulfur dioxide will aggravate the soaking phenomenon of skin residue and affect the quality of wine.
2. Wine aging and storage period: 60 ~100 mg/L.
In order to prevent the oxidation of wine during aging and storage and the activity of microorganisms in grape juice, the content of free sulfur dioxide in wine needs to be kept at a certain level.
The content of free SO2 in wine changes constantly during storage, so it must be determined regularly to adjust the concentration of free SO2 in wine. Before adjustment, take some wine and observe its antioxidant capacity indoors.