WHEN TO START THE HARVESTING?
Years ago when you asked in any small town in the Ribera del Duero about when to start the harvest, anyone could responded, " we will do it in October the 12 th., for the Pilar celebration ...", so that everybody started the harvest at that day because it was when there were more people in town, so family and friends helped to do it.
Fortunately today we have learned the best time to harvest based on technical criteria. Thus, from veraison, when the grapes begin to have red color, we trace the evolution of sugar and acidity and other parameters every week. Typically, we select grapes samples from the entire vineyard , we obtain the grapes juice , so called must, and we check how the sugars are rising every week, that we see through a small device called a spectrograph, while acids are descending.
It is also very important to check the maturation of polyphenols, which are the responsible of the color of wine (anthocyanins), as well as tannins, which will then be essential especially if we develop an aged wine. The maturity of polyphenols also should be checked by tasting the grapes, watching how the seeds are turning from green to reddish-brown color, and the skins (grape skin) are loosing herbaceous flavors and giving more and more intense red color, because the color of Red wine is coming from these skins.
The amount of sugar in the grape juice (must) that we obtained in the sample will determine the probable alcohol of the wine, so that approximately every 17 grams of sugar per liter in the must will be transformed into a degree of alcohol, so when we sampled the vineyard each week and we see that the amount of sugar that has reached the must is approximately 238 grams per liter, it will mean that the resulting wine will rise to 14 degrees of alcohol, so the must is ready in terms of sugar content. Then, if you also see that both the skins and seeds are ripe, it is the time to harvest the grapes.