Racking, which is often referred to as Soutirage or Soutirage traditionnel, filtering or fining, is the process of moving wine from one container to another using gravity. A pump is never used as it can be disruptive to the wine.
There are two main reasons why winemakers rack their wines. The first is to remove sediment. An initial racking is done after malolactic fermentation is complete. Malolactic fermentation, also referred to as malo or MLF, is a process where tart malic acid in wine converts to softer, creamier lactic acid, the same acid found in milk. The process reduces acidity in wine and also releases some carbon dioxide. The dead yeast cells and other solids, referred to as gross lees, accumulate during fermentation that settle over time.
After the first racking, winemakers might then rack additional times to remove what is referred to as fine lees.
The second reason to rack is to provide oxygen to the wine. This impacts its maturation process, managing the tannin in the wine. Oxygenating the wine can also get rid of reductive aromas. These unwanted aromas, often perceived as rotten eggs or tire rubber, can occur when the wine is deprived of oxygen.
The racking process involves the insertion of a stainless steel, wand-shaped device into the barrel. The wine is then siphoned out. The winemaker then uses a sight glass to observe and halt the process when the siphon starts to pull up sediment. The wine continues on through a hose to a tank.
After the wine has been removed the barrel is cleaned. Then the process is completed in reverse returning the wine to the barrel. If the winemaker wants the wine to receive more oxygen, the wand is placed at the top of the barrel so there’s a splashing, aerating effect. If they want it to receive less oxygen, the barrel is filled from the bottom.
The number of times winemakers rack varies. Generally, the more tannic a grape variety, vineyard or vintage, the more times a wine might be racked. Some may rack their wines only once after malolactic fermentation is complete and then again just before bottling. Others might do it every quarter. The winemaker’s vision for the wine is also taken into consideration. A wine that is to be available for consumption early will probably be racked more often than one that is intended to be more age worthy that people are going to cellar for a long time.
All these decisions will impact the wine that ends up in your glass. Who knew?