Destemming is the process of separating stems from the grapes. This process is undertaken before crushing with the purpose of lowering the development of tannins and vegetal flavours in the resulting wine. The grapes are separated from the stems and gently crushed into a pulpy material called 'must'.
The must is dumped in fermentation vats. Some sulphur dioxide is added to avoid any risk of oxidation or bacterial contamination. The must is then inoculated with yeast and fermentation begins. The carbon dioxide that is produced by the fermentation pushes skins to the top of the tank or bin, making a ‘cap’ on top of the liquid. This cap is kept in contact with liquid as much as possible because gives the juice colour and tannins. There are two ways that the cap is kept in contact with the wine: ‘punching down’ and ‘pumping over’. In the process of punching down, the caps are pushed down into the juice. For larger quantities of wine, pumping over is more common: a pump that attached to the bottom of the tank, and the juice is pumped over to the top of the cap and circulated this way for 15-20 min. Either process may be used, but both must be repeated two to four times a day, until fermentation is complete.
To stop the maceration, we drain fermentation tanks. By gravity, the wine (juice) is separated from the fruit skins, which still contain alcohol. We put fruit skins out of the tank and we press it to get back more juice. This press wine has more colour and tannins than the previous one. We can assemble these two types of wine immediately or after aging. At this level, the wine acidity is naturally decreased thanks to the malolactic fermentation.