This is basically distinguished from the above two wine making processes by the fact that the fermentation takes place with the skins, in order to extract the active ingredients (principally tannins and anthocyanins) contained therein.
In the majority of cases the grapes are de-stemmed given the fact that, apart from providing tannin, the stalk also imparts bitterness and astringency. The berries are crushed and, after a light sulfating, the paste is sent to the fermentation tank.
Right from the start of the fermentation, the carbonic gas raises the solids which form a compact mass at the tank top, called the "cap".
In the tank, the alcoholic fermentation takes place at the same time as the maceration with the skins and pips in the grape must. If there are no problems, the complete sugar fermentation takes from 6 to 10 days. The temperature should be maintained below 30 ºC to avoid killing the yeast. The maceration gives the wine colour and its tannic structure. Wines for ageing must be rich in tannins, and therefore undergo a longer maceration lasting 2 to 3 weeks, at a relatively high temperature of between 25 to 30 ºC.
The remontage process, makes it possible to control the extraction of the skin constituents. This operation consists in pumping the must from the bottom of the vat to the top and over the cap, thereby extracting its tannins and anthocyanins.
The devatting involves separating the free run wine from the solids (also called the marc or pomace).
The pulp is then pressed to give a highly tannic, highly coloured press wine. When making a wine for ageing, it is very normal to mix this press wine with a free run wine to provide structure and an intense colour. If the wine is to be consumed young, then it is not generally mixed as this would give high astringency, which can only be rounded out over the years.
Malolactic fermentation is a mandatory step when making red wine. Ideally, after the devatting, the wine should not be allowed to cool down (under 18 ºC). If everything goes to plan, at the end of 2 or 3 weeks, the wine will become saturated with carbonic gas, an event which marks the start of the malolactic process. This lasts between one week and a month (or even more if the cellar is very cold) and, once concluded, the wine is racked and sulfated.
Carbonic maceration is a peculiar form of making red wines, which has a long-standing tradition in the popular "Cosechero" wines, which are prepared by the vine growers themselves.
The key difference with a conventional vinification process lies in the fact that the grapes are not broken before vatting and, therefore, the grapes are neither de-stemmed or crushed. Whole clusters are therefore put into the vat until full (it is an essential condition that these grapes are hand-picked). Carbonic gas is then introduced into the bottom of the tank and, as it is heavier than normal air, the air is expelled to leave the grapes surrounded by a 100% carbonic gas atmosphere.
In this carbonic atmosphere, the grapes develop a special metabolism which starts to transform part of their sugars into alcohol. This transformation is not due to the development of yeasts, the customary micro-organisms, but to enzymatically induced changes.
In this initial phase, in addition to producing a small amount of alcohol (around 1.5 degrees), a series of characteristic aromatic components are synthesized, such as notes of acid sweets, fruit yoghurts, bananas ... They are very easy to detect and identify, as can be verified by sampling any bottle obtained using this peculiar system.
The vinification technique can be divided into two parts:
This technique is used for making young wines, for early consumption, in a great number of wine producing zones.