Some of the most important characteristics of a wine are defined when the grapes are picked. Therefore, it is very important to define, as accurate as the modern technologies allow, the vintage date.
One of the problems that traditionally gives concern to the region's farmers is the grape's late maturation, due to the guiding systems used and the great vegetative profusion which causes shade. The forthcoming of a rainy period after the Summer equinox forces many people to anticipate the vintage, fearing the risk of rot.
The new guiding systems help to achieve a reasonable maturation earlier. This doesn't mean that the vintage is necessarily anticipated, as there is a certain trend to make wine with a higher alcohol content, result of late vintages.
The vintage date should be defined by several factors, among which it's worth pointing out the estimated acidity content. It is known that, as the grapes transform its acids into sugars, the acidity lowers and the estimated alcohol content increases. Each grape variety has its own balance and even each producer may define which relation he prefers. However, the rule should be kept: one should give more attention to this factor.
When the vintage begins, the best transport conditions from the vineyard to the winery should be guaranteed. Everything possible should be made in order that the grapes arrive intact and not crushed or squeezed: the harvest usually takes place in hot days, therefore an early beginning of fermentation might occur.
Once the grapes arrive at the winery, they are transported to the press, being previously grated or not.
The vinification method used for white wines is the must's fermentation after the grapes are pressed without the other parts of the bunch. This is the so called "bica aberta" (fermentation off skins) method.
The red wines ferment in the fermentation cellars (or automatic must distributors), after the grapes are grated. This is the so called "curtimenta" (fermentation on skins) method.
After the «settling», to hold the must until the solid matters have deposited, the white wine's musts are racked into a new container where fermentation takes place.
The alcoholic fermentation is the chemical process of the transformation of sugars into alcohol. This process is caused by yeasts, being sometimes necessary to add them for the process to begin. In this case, the vine growers may use the selected yeasts offered by the CVRVV or produce, in the beginning of the vintage, an amount of yeasts from their own musts.
It is important to point out the fermentation temperature. During this process the must produces heat and raises its temperature. Experience tells us that temperature increases one degree centigrade for each alcohol degree of must. This means that a must, that starts the fermentation at 15º C and 10% vol. will reach a temperature of around 25º C.
The temperature acts on the fermentation development, impossible to occur below the 12º C and the higher the temperature, the faster the fermentation takes place. However, the higher temperatures "kill" the yeasts responsible for "working" the aromas, and favours the appearance of unwanted volatile acidity. It is therefore of extreme importance to control the temperature, what may extend the must's fermentation time to three or four weeks.
The are many ways, more or less sophisticated, of controlling the fermentation temperature - from electric operated refrigeration systems to ordinary showers over the stainless steel vats and fresh wineries.
The wines are encourage to undergo a second, or malo-lactic fermentation. In the event of wines with a high non-volatile acidity, and therefore rather "astringent", the malo-lactic fermentation improves the quality.
This fermentation is a biochemical process through which the malic acid, abundant specially in grapes not completely ripened, changes into two elements: the lactic acid (present in milk and responsible for its sourness) and the carbon dioxide. The malo-lactic fermentation is then responsible for the natural carbon dioxide found in the Vinho Verde wines, giving them its traditional "petillance".
However, the occurrence of the malolactic fermentation has its costs: a reduction of freshness and primary aromas proceeding from the grapes. For this reason, many oenologists prevent its occurrence in the white Vinhos Verdes, which must have freshness and young aroma. The malolactic fermentation mainly is encouraged in the red Vinhos Verdes, whose quality depends more on its flavour complexity than the aromas intensity.