Pressing

Pomace, which is the skin, pips and stems of the fermented grape, still contains wine after devatting; it must be recovered. To do this, the pomace is subjected to a pressing operation which consists simply of exercising pressure on the wet mass in order to separate the liquid from solids. The pressure is gradual and the wine flows little by little, the first amounts being of good quality, the following having more colour and roughness. The final amounts are very rough and have very little alcohol; the wine has already mixed with the water contained in the stems.

There are very few villages in the Rioja, where traditional methods are used, which have presses. Where they exist they are usually of the vertical type moved by hand or with an electric motor. The wineproducers take turns to press their pomace. Sometimes, there is some delay and the pomace is pressed when it is hot and aired resulting in a pressed wine which is a little vinegary.

The initial wine obtained from pressing is of good quality but those obtained with intermediate or heavy pressing are of lower quality. This, technically known as "obligatory wine delivery", is a measure imposed by the government whereby wine, which does not reach minimum quality levels, is sent for distillation.

Industrial bodegas work with several different types of presses. Some of them still use vertical presses similar to those used by wineproducers. Others use a horizontal rotary press and still others a continuous press or the rotation of a helical screw-spindle.

Horizontal stainless steel and wooden press.

Quality is influenced not only by the use of pressure, but also by the quality of the materials with which the press is made. Wood and stainless steel are considered as being fine materials, while iron has a negative effect.

For obvious reasons, to make white and rosé wine, the skins and stems are removed before fermentation. Therefore, the pressing operation is carried out with fresh grapes and the liquid extracted is must. Musts which flow after the effect of the heavier pressure are of poor quality, inadequate for making wine. They have a low alcohol level, a brown colour and a herbaceous taste. These fermented musts are also used for the "obligatory wine delivery".