The Birth of our wines
As mentioned earlier, harvest time at López de Heredia is hectic, but organized in such a way that there is no delay in receiving the grapes arriving in the containers via tractor-drawn trailers. It is essential that there is no delay because waiting can produce very prejudicial fermentation in the containers.
This is why there is a harvesting train for red grapes and another for the white. Red grapes are destemmed before going to the fermentation vats, while white grapes are crushed, thus immediately releasing their must - it is undesirable that the must should be in contact with skins.
Emptying the vats after the first fermentation
The difference between red and white wines lies in the fact that with red wines fermentation occurs while the liquid is in contact with the skins, which contain the colourant, whereas with white wines the must ferments on its own. With rosés, the process is mixed: the skins remain in contact with the must during a period of maceration (soaking) so that some of the colour can be absorbed, but are then removed before fermentation begins.
The must is fermented in large oak vats. The biggest, with a capacity of 240 hectolitres, are for red wine, while the smaller vats (60 hectolitre capacity) are for whites. Yeasts are vital to the quality of the wines since they cause fermentation; these micro-organisms are typically found in the soil, and are spread over the grape skins by insects and the wind. The main microflora in La Rioja are Scharomyces, Kloekera apiculata and Tomlaspora rosei.
During the biological process of fermentation carbon anhydride is emitted as the sugars are transformed into alcohol. Although the temperature never exceeds 36ºC, bubbles disturb the surface of the vat as if it were boiling - hence the popular term of "tumultuous fermentation".
During the vinification of the red wines, the solid part of skins and pips (the marc) form a thick floating layer called a cap, which has to be circulated in order to activate the oxygenation of the yeasts. This process of “pumping over” makes the maceration more homogeneous and helps the extraction of colour. The tumultuous fermentation usually lasts about seven days, during which time the must becomes wine. However it maintains a certain percentage of residual sugar which has to be removed in a slower subsequent fermentation.
Before initiating the second fermentation for red wines, the wine is drained from the vat in order to separate solids from liquids. This second fermentation should take place in Bordeaux-type oak barrels, and can take up to five or six months. The result is a softer, more perfect wine.