Making of port, what makes port different from table wines is fortification. Port, part three.
The making of vintage port differs enormously, depending on a lot of variables, like the ripeness of the harvested grapes, the winemaker, facilities of the winery and preferred style of port. The same is true for the method of fermentation. The method used varies according to preference of the producer or winemaker. There are five principal stages in port making: harvest, pressing, fermentation, fortification and ageing.
After the hand picking at harvest the grapes are delivered to the winery with a bit over sulphur over them to stop oxidation. On arrival in the winery the grapes are evaluated by the wine maker and inspected on a sorting table before being crushed and de-stemmed. Some producers remove the stems, some not. The varieties are customarily fermented together. Each grape variety contributes its own particular character, such as the intense flavours of woodland fruit, delicate floral scents, exotic spicy notes or the wild resin aromas, to the nose of the wine.
There are two main methods of fermenting port: lagar and non-lagar. The most traditional method of fermenting is the lager or in its newer version the robotic lagar.
In the traditional process the grapes are then placed in wide, thigh-deep granite treading tanks known as lagares. Here they are trodden by foot. The human foot breaks up the grapes without crushing the pips that would release bitter tasting phenolics into the wine. Lagares are trodden for 3 to 4 hours by the teams of workers. On average 1-2 people are required per pipe and 20 man hours per pipe. The cap of skins and stalks are subsequently pushed down with long spiked sticks. Lagares do not require external power but are it is very labour intensive and expensive in terms of workforce.
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 tread individually, moving freely around the lagar ensuring that the grape skins are kept submerged under the surface of the wine. After a few hours the fermentation begins and the heat and alcohol it produces begins to release the colour, 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. This phase of the process is vital to the making of quality Port. Treading is still the best way of achieving gentle but complete extraction, producing wines with structure, depth of flavour and balance. Similar results have been achieved by mechanical extraction systems.
Robotic lagares were designed by Symington’s to simulate human treading. A shallow, rectangular stainless steel tank, approximately the same size as a traditional lagar, was adapted to carry a self-propelled gantry with silicon covered robotic tooth like feet. The gantry moves up and down the lagar with the silicon feet copying the action of human feet. Another advantage of the robotic lagar is a system of panels in the pistons and three sides of the lagar which are filled with water. This water can be cooled or heated up to 37 degrees Celsius to imitate the human body temperature. After treading, the short 2-3 day fermentation is monitored and when the fermenting must is ready
to fortify. Robotic lagares can be used for premium quality Port.
Autovinifiers are an early attempt to automate the lagar process. Grapes are placed in closed tank (cement or stainless steel) with an open trough above it that is sealed. During fermentation skins rise to the surface of the juice to make a cap. Carbon dioxide is trapped at the top of the tank. Carbon dioxide pressure pushes juice from the bottom of the tank up a tube to the trough at the top. At a set pressure the gas is released. Juice runs back into the tank and must sprays over the cap. This process repeated at regular time intervals. Autovinifiers require no external power source and were ideal when the Douro had an erratic electricity supply.
Pumping over is a process where the must is pumped from the bottom of the tank and sprayed over the cap to break it up. It is essential that “punching down” or “pumping over” is performed diligently to obtain the maximum extraction in a short period of time, although it is not suitable for high quality port as it does not extract a sufficient amount.
In order to extend production and allow treading on a larger scale Taylor’s developed a fermentation tank fitted with a system of piston-driven plungers, familiarly known as ‘Port toes’. Piston Plungers are round, shallow open topped stainless steel vats where the cap is pressed down with robotic pistons. Working asymmetrically, these plungers provide the same constant but gentle skin contact achieved in the lagares by the pickers’ feet.
A rotovinifier is a device in which the must is placed into a sealed vinifier that rotates, or the inner shaft rotates independently. This stops the cap forming and keeps the skins in contact with the must giving good extraction.
Fortification is done when approx one-third of the sugar has been converted to alcohol. 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 wine is fortified to approx 20% ABV with aguardente a 77% ABV neutral grape spirit. The process of beneficio (mutage) halts the fermentation, killing the yeasts and preserving the natural sweetness of the grape in the finished wine. The quality of the brandy is very important. Over time, when the wine ages, the spirit and the wine will synergize, a process that contributes enormously to the subtle complexity of the mature Port.
The process of fortification is virtually standard for the entire port making. The ratio is 1:4, 110 litres of alcohol to 440 litres of grape must. This makes 550 litres, the average size of a Douro pipe. The alcohol is generally injected into the must the moment the must is being racked. The new port is then mixed for a few hours. The acetaldehydes in the spirit ensure that the anthocynanins (colour) and polyphenols (or tannins, naturally occurring plant polyphenols) are broken down. The wine gets darker after fortification. Once the port is mixed winemakers make adjustments like adding tartaric acid to increase the acidity. Other producers do this before fermentation. White and rosé Ports are made With a lesser degrees of maceration, but otherwise all Port wines follow the same production method.
After the fortification the wine remains at the winery in the Douro Valley where it is left to settle until the spring of the following year. In spring the young Port wine will being taken to the firm’s Port lodges at Vila Nova de Gaia near the Atlantic coast to be matured, blended and bottled.
Before it is taken to the ageing lodges, each wine is evaluated and a decision taken as to the style of Port for which it will be used. It will then be placed in casks or vats 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.