The new wine is raw, cloudy and gassy. It is aged between the end of the alcoholic and/or malolactic fermentation and bottling.
This period is more or less long depending on whether we are dealing with “primeur” or “garde” wines. Its duration is between 1 to 2 months up to several years like the Spanish red wines Gran reserva with 60 months in total, 18 of which are in barrel.
The maturing process includes a period of refining. It corresponds to the elimination of the most important sediments by decanting, sticking, filtering or racking as well as the C02 coming from the fermentation. Some controlled oxygenation of the wine can be beneficial depending on the style desired. For example, for red wines, it is beneficial to soften the tannins. Racking in the presence of air as well as the wood of the barrels are means to achieve this.
Thus the maturation has several goals: purification and aging for an aromatic and structural evolution of the wine.
There are several sizes for both tanks and barrels.
For the wood, everything depends on the size of the barrels which have different names according to their capacity and the wine making regions:
- tuns which correspond to several barrels up to 2500L or more
- 225L barrels (Bordeaux style) or 228L barrels (Burgundy style, also called “pièces”)
- the Bordeaux barrel is 900L
But not only…In Burgundy, France, they still use other sizes and names:
- muids : with a capacity of 1200L
- ½ muids : 600L
- The tail which is equivalent to 456L
- The leaflet has a capacity of 114L
For the tanks, the choice is eclectic.
They come in all sizes, but the winemaker will generally opt for tanks smaller than 5,000L. They can also take various forms. The most classic ones, found in most wineries, are cylindrical in nature.
However, there are other less common lines, such as ovoid, cubic, pyramidal, truncated cone or square tanks. The shape of a tank gives it specific properties that will influence the final result of the winemaking process.
Type of tanks
Several types of tanks exist:
- Concrete tanks: they offer a good thermal capacity, but meticulous maintenance is required to prevent the occurrence of false tastes. They cannot be moved.
- The concrete egg or the ovoid tank created by Nomblot, for example, which allows a permanent circulation of the lees during the maturing process thanks to the formation of vortexes in the tank. This eliminates the need for brewing. The wines produced are generally fatter and more concentrated. This type of container is sought after by producers of organic, natural or biodynamic wines for the gustatory sensations it brings.
- Stainless steel tanks are the most used today because of their ease of cleaning and chemical neutrality. They are usually equipped with temperature controllers. It can be a double outer shell or internal coils where a hot or cold liquid circulates.
There are also some of older tradition:
- The terracotta amphora was the first container in which wine was made. It was used in Georgia 7000 years ago. It has regained a certain notoriety among natural wine producers in Greece and Spain. Often the amphorae are buried to reduce temperature variations. However, the container is fragile, hence its low popularity.
What are the reasons behind the choice of the container?
Micro-oxygenation is the main factor.
The addition of oxygen is synergistic with the maturation on lees of white wines. It contributes to the increase of the perception of fatness and also participates in the increase of astringency, which can be interesting for wines with a soft balance, but which must be taken into account for wines balanced on acidity (more aggressiveness).
Oxygenation will also soften the tannins and stabilize the color for red wines.
The wine aged in tuns has little contact with the wood but more with the oxygen. This reduces the risk of wine reduction that can occur in tanks that are too tightly sealed.
The woody aromatic notes will be more or less marked depending on the oxygenation, the origin of the wood, its preparation (torrefaction of the staves), the size of the container or its age. Different aromas will manifest themselves for example, vanilla, smoky, caramel, tobacco, etc. The adjustment of these will be done on the proportion of new barrels and their composition (type of wood: American oak, French oak, etc.) as well as the duration of aging. Indeed, the younger the barrel, the more important the role of the wood in the transmission of aromas.
Not forgetting the lees, which are sometimes stirred to improve the complexity of the wine and act as a reducing buffer because they consume a lot of oxygen.
The wood requires a certain rigor because too pronounced aromas could mask those of the wine. Bacteria in the wood could ruin it as well. Finally, evaporation losses (the angels’ share) must be taken into account economically.
The concrete tanks also have a phenomenon of micro-oxygenation. The final product is very aromatic with the taste of the fruit and the land.
The stainless steel ones are totally neutral and hermetic. The wine will keep its freshness and its aromas without developing others. It is therefore reserved for wines that can be enjoyed in their early years. It is suitable for all types of grape varieties, protects against oxidation and allows for temperature control. But it is not very suitable for more complex wines.
It also has its shortcomings such as the lack of oxygen which will require more racking as well as more clarification efforts.
So tank or wood?
Finally, it is the final complexity of the wine that will be decisive for the winemaker. He will orient his choice towards a particular container, each with its advantages and disadvantages. We must not neglect the traditional or even regulatory part of winemaking which varies from one region or country to another because it will mark the typicality of the wine tasted.