Wine production process
Either white or red grapes are fed into a crusher-stemmer which tears off the stalks and pumps the broken grapes into a pneumatic press. The press revolves and an airbag inside is inflated, pressing the grapes against the cage. The marc (skins) is left behind as the must (fresh juice) falls into a trough, from which it is pumped into a fermenting vat, after which there are several courses open to it. It may be made into sweet wine by having its fermentation stopped while it still contains sugar, or be bottled before fermentation is finished, to make sparkling wine. Or it may be fermented until all its sugar is used up, to make dry wine. And finally, the dry wine may be distilled to make brandy.
Red grapes are fed through a crusher (or often a crusher-stemmer) and pumped into a vat where they ferment in contact with their skins.
Traditionally the stalks go in too but nowadays, they are usually removed . The wine gradually draws out the colour and tannin from the skin. Fermentation is allowed to go on until all the sugar is used up (up to 14 days). Then, a tap is opened and the 'free-run' wine runs off. For lighter, quicker-maturing wine, the modern practice is to take the wine off the skins after a few days to finish fermentation separately. The skins are traditionally pressed in a hydraulic basket press by a descending plate which forces the juice out through slatted sides. Layers of matting help the juice to run out. This press wine (vin de presse), deeply coloured and tannic, is usually mixed with the free-run wine. The marc left in the press is either used as fertilizer or distilled to make cheap brandy.
Red grapes are fed through a crusher and straight into a vat complete with their skins to begin fermentation. The juice for rose wine takes on a light pink colour from the skins but it is run off almost immediately into another vat to ferment on its own. Normally it is allowed to finish its fermentation naturally, hence is completely dry.