In red wines, fermentation is the transformation of sugars into alcohol, carbon dioxide and heat through the action of yeasts, but it includes other processes depending on whether one is making a wine to be drunk in its youth, or one to age.
Once the grape must is macerating with the skins in a stainless steel tank, we can add the yeasts or let fermentation start spontaneously with the indigenous yeasts present on the grapes themselves. We will still want to control the temperature of this procedure just as we do with white wines, although the ideal fermenting temperature for red wines is slightly higher than for whites.
If we want a young red wine, once we have extracted the desired degree of colour we will rack off the must, separating it from the grape skins, and finish the fermentation of the must-wine in another tank. If we want to make a red wine for ageing, we’ll need to wait longer until all the colour and structure has been extracted from the skins, and in all probability, when we rack the wine off, the fermentation will already have finished.
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