It is a life-size decanting, a "cleaning-up" of the wine. The purpose of racking is to separate the wine from its natural lees during maturing. By this operation, the winemaker eliminates the deposits that have become undesirable, made up of fermentation residues and precipitated tartar that accumulate at the bottom of the barrel. Prolonged contact between these residues and the wine can lead to aromatic deviations, reduced, bad tastes and even some times disease and bacterias.
In concrete terms, the wine is transferred from barrel to barrel first by gravity then draining or pushing by neutral gas. For red wines for laying down, racking is often done with intermediate aeration. The operation, through subtle chemical reactions, flavors the formation of aromas and the maturation of tannins, fixes the color and reduced odors. The moment of racking is determined by the wine maker and master cellar. Here again, the "best" is the enemy of the "good": too many rackings can oxidize or deplete the wine.
The best way to do it is to use a candle, as only natural candlelight will allow the winemaker to see the sediments and deposit through the glass.
The quality and number of rackings have a huge influence on the success of the ageing process and the final product. Practices differ according to the region, the grape varieties, the color and nature of the wines, the vintages and the barrels. Usually in Bordeaux racking is done every 3 month for a total of ageing of 15 month.
"When the rackings are carried out at the right time, the result is wines with a clear, more brilliant color and brightness. They are marked by great purity and a crystalline aspect, both in terms of aroma and taste. On the nose and in the mouth, you can detect a beautiful expression of fruit and aromas. The wines gain in substance, complexity and flavors. They are also more frank and easier to approach. On the other hand, if you find not very bright color or some bad taste, you can deduce that the racking was badly done or made at the wrong time. So, Racking is a crucial and decisive stage in the maturing of wines.
THE WINEGROWER'S GESTURE
There are several ways to extract. One of them is racking by draining the wine and then pumping it out with intermediate aeration, as here in Burgundy.
1) The winemaker tilts the barrel slightly.
2) The wine flows into a container where it is aerated for a few minutes. The lees remain in the barrel, which is then washed.
3) The wine is then pumped back into another barrel, which is clean with hot water.
4) The empty barrels are cleaned and sterilized by burning some sulfite tablets inside
5) The barrel is full-up with new clear wine.
See how it works on the next video, filmed in the cellar of Chateau Lafite Rothschild