The Birth of our wines
During the grape harvest at López de Heredia's work goes at a hectic pace, but organized so that there is no delay in receiving the grapes arriving in the containers on the tractor - drawn trailers. There must be no delay because waiting can produce very prejudicial fermentation in the containers.
This is why there is a harvesting train for the black grapes and another for the white. Once the containers have been emptied into the hoppers of the pressing machines, for red and rose wine the stalks are removed by a stalk-remover, but for white the presser merely breaks the grapes so that they can release the must straightaway. They need to ferment without peel so that the wine does not have too much colour.
Emptying the vats after the first fermentation
The difference between reds and whites lies in the fact that for the reds the must ferments with the peel, which contains the colorant, while for the whites the must ferments on its own. For the rosés there is a mixed elaboration: the peel stays for some time with the must in maceration so that the must can take its colour, but it is removed before fermentation begins.
The must ferments in big oak vats. The big ones, with a capacity of 240 hectolitres, are for red wine and the small ones, 60 hectolitres, are for white. What is on prime importance in the quality of the wines are the yeasts that produced in the fermentation, those micro-organisms found in the soil which insects and the wind spread over the grapes. The main microflora in La Rioja are the "Scharomyces", the "Kloekera apiculata" and the "Tomlaspora rosei".
During fermentation there is an emission of carbon anhydride in the biological process whereby the sugars are transformed into alcohol. The bubbles which disturb the surface of the vat as if it was cooking, although the temperature is never more than 36 degrees, explains the generally used term of "tumultuous fermentation".
During the vinification of the red wines, as the must ferments with the marc, these form a thick floating layer called a "hat", which has to be removed to activate the oxygenation of the yeasts. It also makes the maceration more homogeneous and helps the extraction colour. The tumultuous fermentation usually lasts about seven days, during which time the must becomes wine. However it still keeps a certain percentage of residual sugar which has to be removed in a slow second fermentation.
For red wines the purpose of the second fermentation, which should take place in Bordeaux - type oak casks, is to separate it from the solid parts.