Definition - What does Lees Stirring mean?
Lees stirring is a step in the Sur Lie winemaking process; it involves stirring the wine to ensure that the lees impart all of the characteristics into the wine that the winemaker wants. Most commonly used for white wines, lees stirring reduces negative aromas, assists in the release of important characteristics into the wine, imparts creamy, viscous mouthfeel and encourages the formation of more complex flavors and better length. In addition, lees stirring integrates wood and oak characters, and promotes secondary reactions.
WineFrog explains Lees Stirring
Lees are the dead yeast cells that remain in a wine during secondary fermentation. When a wine is made Sur Lie, the intention is to leave the yeast cells in the wine in order to impart depth and character to the wine. The Sur Lie process is used only for white wines, since red wines usually keep the lees anyway as part of the winemaking process. It is used for stylistic reasons to enhance structure and mouthfeel of wine, give it body, increase aromatic complexity, flavor, aroma, depth and length.
Lees absorb oxygen, assisting in a slow, controlled oxidation during the wine aging process. The stirring of lees is conducted on "fine lees" with "gross or heavy lees" being sifted out due to the negative impact too much lees have on wine. Fine lees in wine mean that there is one micron to few tens of microns in the wine. These lees remain in suspension for longer than 24 hours.
There is a slight risk of negative aromas and flavors being imparted into the wine if the lees are inappropriately managed. There are two ways to stir lees - moderate or single barrel, where a steel rod with a paddle at the end is placed in the tank or barrel and spun with an electric drill attached and small scale, where a food turntable is used to externally control the stirring process.