Chapter 6

Wine Fermentation

Racking Wine after Fermentation

The first racking is conventionally done at the end of alcoholic fermentation when the solid parts begin to sediment on the bottom of the fermentor. If malolactic fermentation is desired, typically for red wines, racking is delayed until it has come to completion (Chapter 7). In some cases, the wine is racked off from the fermentor immediately into barrels, as malolactic fermentation in wood has been shown to enhance aromatic complexity as well as the finesse of oak character.

Racking Operations

Wine tanks are equipped with outlet valves. The bottom one can rack off all the liquid from the tank. The second valve is located about 20 to 30 centimeters (cm) (7.8-11.8in) above the bottom one. In most cases the lees layer is somewhere below the level of the second valve. Therefore, racking off the wine from its solids content is done from this valve. Manual draining by gravity is adequate where volumes are small and labor costs are low. For most large wineries, however, manual racking would be prohibitively expensive, both in terms of time and labor.

Blending

After the first racking, although the wine is in a somewhat raw condition, an experienced winemaker can get some idea of the quality of the finished wine. It is at this stage that the first round of tasting occurs, with a view to the ultimate blend that will make up the final wine.

Adjusting Sulfur Dioxide Levels

If not undergoing malolactic fermentation sulfur dioxide levels need to be maintained to prevent oxidative browning of white wines and potential spoilage organisms.

Aeration of Wine

Although modest oxygen uptake during racking assists color stability in red wine, its value in white wine maturation is more controlled.

White Wine

A white table wine with a fruity aroma should be racked early. White wine should be racked gently and excessive aeration should always be avoided. Uncontrolled aeration of wine (during racking) causes a loss of fruitiness and a darkening of color.

Red Wine

A key difference in racking red wine as opposed to white is that in red wine limited aeration during racking is desirable since it helps in maturation. Young red wines are rich in phenolic compounds that can impart an astringent and bitter taste to wine.

Malolactic Fermentation

In racking red wine, one of the first things to consider is malolactic fermentation. If malolactic fermentation has not occurred and you intend to encourage it, then leave the wine on the lees, and maintain conditions favorable to malolactic fermentation. Following alcoholic fermentation and malolactic fermentation, the wine is racked from the fermentation vessel and transferred to settling tanks or directly to maturation vessels.

Click on the following topics for more information on wine fermentation.