There are actually a wide variety of fortified wines in the world, for which Port is just one kind. But it is a special one, and of the fortified wines, it is the oldest. Fortifying means that a grape spirit, or brandy, is added to the wine to help preserve it. The brandy is added during fermentation, which then kills the yeast as the yeast can only survive in an environment that is just so high in alcohol. This means that wine retains its sweetness. From here, the wine goes into a series of ageing containers. Depending on how long the ageing process is, the wine maker is making Ruby or Tawny port.
Around mid-September, the grapes are picked by hand. Port wine is made from a wide range of traditional grape varieties, most of them native to the Douro Valley. Seldom found elsewhere, these varieties are perfectly suited to the hot, arid conditions of the Douro Valley, and are the source of much of Port’s unique and distinctive character. The best-known red varieties include Touriga Francesa, Touriga Nacional, Tinta Roriz, Tinta Barroca, Tinta Amarela, and Tinto Cão. In total, there are around thirty types of Port grapes. Most of these varieties have relatively small, thick-skinned berries, which produce the dense concentrated must (grape juice) needed to make Port.
Although they may be planted separately, the varieties are normally harvested and fermented together. Each grape variety contributes its own particular character, such as the intense flavors of woodland fruit, delicate floral scents, exotic spicy notes, or the wild resiny aromas of gum cistus. The grape varieties work together like instruments in an orchestra, to create a subtle, complex, and multi-dimensional harmony.
Traditionally when the fruit arrives at the winery, it is evaluated and inspected on a sorting table before being de-stemmed. In the traditional process, still used to make port in some places, the grapes are then placed in wide, thigh-deep granite treading tanks known as lagars. Here they are trodden by foot.
The first stage of treading is called the corte, or “cut,” and involves crushing the grapes, which at this stage are still relatively solid, to release the juice and pulp from their skins. During this initial stage the treaders link up in a tight line and advance very slowly shoulder to shoulder across the lagar, treading methodically and in unison to ensure that the grapes are thoroughly crushed. When the corte has been completed, the second stage begins. This is called the liberdade or “liberty.” The treaders now work individually, moving freely around the lagar ensuring that the grape skins are kept submerged under the surface of the juice. After a few hours, the fermentation begins, and the heat and alcohol it produces begins to release the color, tannins, and aromas from the skins, allowing them to be diluted in the fermenting wine. The treading is sometimes supplemented by the use of long wooden plungers, called macacos, used to punch the skins down under the surface of the wine.
Using people labor is quite expensive, but research has proven that foot treading is still the best way to achieve complete extraction. Because the wine will only be fermented for a short time, it is important to get the most color and flavors out of the skins quickly. The foot treading doesn’t chew up the skin like mechanical crushing would. The advantage here is that no harsh tannins are introduced into the wine. Pneumatic foot pedals are sometimes used in bigger operations.
When about half of the natural sugar of the grape juice has been turned into alcohol via fermentation, the wine maker gives the signal for the fortification process to start. The treading stops and the skins are allowed to rise to the surface of the lagar, where they form a solid layer. The wine fermenting under this cap of skins is then run out of the lagar into a vat. As the fermenting wine pours into the vat, a very clean young wine brandy is added to it. This colorless neutral spirit, which is around 77 percent alcohol, is added in a ratio of about 115 liters of brandy to 435 liters of fermenting wine, although this proportion can vary.
The addition of the spirit raises the strength of the wine to a level where the yeasts responsible for fermentation can no longer survive. The fermentation stops before all the sugar in the juice has been turned into alcohol, thus some of the natural sweetness of the grape is preserved in the finished wine. It is important to use high-quality brandy at this stage because it will affect the quality and final flavors of the port. As the wine ages, the spirit and the wine will combine in a magical synergy, which will contribute to the subtle complexity of the mature Port.
After the harvest, the wine remains at the winery in the Douro Valley, where it is left to settle until the spring of the following year before being taken to the firm’s lodges at Vila Nova de Gaia near the Atlantic coast, to be matured, blended and bottled. In former times the Port wine would travel down the river Douro to the coast in special wine boats called barcos rabelos, but nowadays it travels overland by road. The government decided to build hydroelectric dams on the river, which ended this tradition in the 1950s.
Before it is taken to the ageing lodges, each wine is evaluated, and a decision is made as to the style of Port for which it will be used. It will then be placed in casks or vats, as appropriate, to begin the ageing process. Port, being fortified and a wine of remarkable ageing potential and longevity, can remain in wood for much longer than most other wines. This means that it can be aged in different ways and for different periods to produce a wide range of different styles. This diversity of different styles is one of the most fascinating aspects of Port, making it one of the most diverse and adaptable of all wines.