Maturation of Wine
Racking, moving wine from one vessel to another, plays a valuable role in wine maturation. As previously mentioned, racking is generally done shortly after primary fermentation to discourage malolactic fermentation and to separate the wine from the lees, which usually consists of macerated grape tissue, seeds, and dead yeast cells that settle to the bottom of the tank. This helps clarify and freshen the wine by removing the lees or sediment. After the wine has finished malolactic fermentation, if required, it may be racked again. By removing microbiological spoilage organisms (e.g., Brettanomyces), racking enhances microbial stability.
Frequency of Racking
Racking for light, fresh, aromatic, dry white wines is not as frequent. If this type of wine is racked at all, care must be taken to keep aeration to a minimum. Uncontrolled aeration of wine (during racking) causes a loss of fruitiness and a darkening of color. To minimize air contact and oxidation, many vintners rack wine under a nitrogen or carbon dioxide blanket (Section 17.4).
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