Winemaking throughout the ages
Until about 1756, the making of shipping wines, as Ports were called in those days, followed the so called 'ancient winemaking' techniques. The addition of grape spirit (and only in very limited amounts) only occurred after fermentation was complete so the wines that were made were dry.
In 1820, a new method for adding grape spirit (the so-called modern winemaking technique) was applied whereby grape spirit was added to stop fermentation, thus creating a sweeter wine to the taste. This method only became widespread in 1852 when Ports began to take on the characteristics we know today.
Port is a fortified wine, whose production differs from the methods used for still wines mainly because it is left to ferment and to macerate for a very short period of time (2 to 3 days). Furthermore, the addition of brandy has to respect certain rules that have been fine-tuned over the years by tradition and practice.
According to traditional winemaking methods used for making certain types of Port, after the grapes have been destemmed (separated from the stalks), they are crushed in lagares (open stone treading tanks with a maximum depth of 60 cm). The treading is traditionally performed by men and women although it may also be done with mechanical devices that simulate the action of the feet. After the first such pressing, the fermenting must is left to rest for some hours, after which it is again pressed until such a time as the fermenting must is separated from the solid matter in the juice (running off) and the brandy is added.
Today, most of these wines are made in highly technical wineries that associate quality with profitability. In these wineries, most procedures are mechanised. Once the grapes have been fully or partially destemmed, the grapes are pressed and pumped into vats where they ferment for 2 to 3 days. During this period the juice is pumped over several times to extract the maximum of colour from the skins.
White wines may be made differently. According to the traditional methods, they are made with some maceration and in these cases it ages in conditions that lead it to oxidise. The time of maceration is reduced for wines in which the winemaker wishes to keep a pale colour and the fresh aromas.
It is essential that the type of grape spirit that is to be added to the fermenting must be very carefully chosen as its chemical composition and aromatic potential are fundamental to making a high quality Port.
The Port and Douro Wines Institute enforces a very rigorous system for controlling all the batches of grape brandy that will be used for making Port. Control of the quality of the grape spirit is carried out through laboratory analyses and tastings.
FORTIFICATION WITH BRANDY OR BENEFÍCIO
Fortifying the wine with grape spirit gives the wine specific organoleptic characteristics, improves the chemical stability and at the same time helps control the final degree of sweetness of the wine. Thus, fermentation must continue until the amount of unfermented sugars in the wine gives it the desired sweetness. The fermenting must is then separated from the solid matter (run off) and pumped into vats where the fermentation is stopped by adding grape spirit in set proportions.
The table below shows some values that help in understanding just how the winemaker determines when to add the grape spirit to the fermenting must. Thus, to obtain a Port with 19% alcohol by volume and with a sweetness corresponding to 2º Baumé (Bé), grape spirit must be added to stop fermentation when the fermenting must reached a volumetric mass (p20) of 1.0296. At this moment, 83 litres of grape spirit are added to 467 litres of must; the resulting semi-sweet fortified wine then presents values of 76 grams of residual sugars per litre of wine.
The process of ageing a Port may take several dozen years and varies according to the type of wine one desired. After the wine has first been racked from the lees, during the winter that follows the vintage in which they were made, the wines are tasted and classified according to their sensorial characteristics.
The finest blends of wines produced in a year of exceptional quality are usually set aside with a view to their being declared a Vintage. However, most of the wines are used to prepare blends that have special characteristics and obey to pre-set standards of quality. Blends are made in large vats that have stirrers or with pumping over circuits.
During their first two years, the wines are frequently racked from the lees and aired, as often and as intensely as required by the characteristics that the winemaker wishes the wine to develop as it ages.
Vintage and Late Bottled Vintage (LBV) Ports usually begin ageing in cask - 2-3 years in the case of Vintage and 4 to 6 years in the case of Late Bottled Vintage. After these wines are bottled, the characteristics improve considerably as their bouquet develops with little possibility of oxidation. The longevity of these wines, due to their wealth of polyphenols, is extremely high (usually a maximum of about 20 years in the case of Vintage and of about 5 years in the case of LBV, although these frequently continue to improve for many more years.).
All the remaining types of Port are aged under oxidising conditions: less so in the case of Ruby Ports (that thus retain a varying intense dark red colour and the vigour of young wines), more so in the case of Tawny, Dated and Ports with an Indication of Age. As the wine ages through oxidation, it loses the harshness provoked by its tannins and develops an admirable rich and complex bouquet. The variations in colour caused by oxidation as these wines age are considerably marked. The intense, deep colour of young wines gradually gives way to lighter shades of golden red until it attains the golden colour that is typical of old Tawnies.
White Ports may be produced with some maceration and aged through oxidation although the latter process is not encouraged if one wishes to retain a complex floral aroma and a pale, lemon colour.
The way by which one stores Port will have a fundamental effect on the changes that occur to the wine and to its composition. Hence, the type and capacity of the containers must be adapted to the evolution that one wishes for the wine. Port is usually stored in typical Douro casks called pipes, in large casks (25,000 to 35,000 litres) or in vats (550,000 to 750,000 litres).
The storage capacity in wood represents more than two thirds the total storage capacity. The wood that is most often used is Portuguese oak although chestnut and other exotic woods also used. The large cylindrical vats in stainless steel and lined approximately 10% of the total capacity and are only used for the temporary storage of wines.