Published on January 22, 2008
PORT WINEPROCESSING LINE: PORT WINE PROCESSING LINE PROCESSING LINES CVUT Mechanical Engineer Nuno Silva Porto Portugal HISTORY OF PORT WINE: HISTORY OF PORT WINE PORT WINE PROCESSING LINE CVUT Mechanical Engineer - The first vineyards in Douro were planted in the thirteenth century during the reign of Dom Diniz. - By the end of the 17th century, relations between Britain and France had deteriorated so badly that the British government decided to impose heavy import duties on French wines, and the discovery was made that the wines from the Douro valley were to the taste of the British. Slide3: PORT WINE PROCESSING LINE CVUT Mechanical Engineer Port can legally still only be produced in the Douro region within boundaries firmly delineated by the Portuguese government. It remains to this day the center of much of the world's production. Three main factors account for the difference between one port and another: - The quality of the grapes and the soil in which they are cultivated - The blend of wines selected for each style of port - Whether the port is matured in the bottle or in a wooden cask Slide4: PORT WINE PROCESSING LINE CVUT Mechanical Engineer Forming a deep cleft in the rock, the river Douro flows at an altitude of between 60 and 140 metres above sea level. The terrain either side of the Douro is irregular in the extreme with deeply incised tributaries draining the mountais, which rise in places to over 1000 metres on the edge of the region. - Half of the region’s vineyards are planted on slopes SOILS AND CLIMATE Slide5: PORT WINE PROCESSING LINE CVUT Mechanical Engineer SOILS AND CLIMATE Slide6: PORT WINE PROCESSING LINE CVUT Mechanical Engineer - The Douro’s soils are naturally rich in Potassium and magnesium but tend to lack calcium and boron, causing a condition known locally as moromba. This was originally thought to be a virus, but is now successfully treated by applying borax to the soil. -The proportion of organic material in the Douro’s soils is low and regular application of both organic and inorganic fertilisers is necessary to correct the imbalance of nutrients. SOILS AND CLIMATE Slide7: PORT WINE PROCESSING LINE CVUT Mechanical Engineer The feature that all the vineyards have in common is the initial deep ploughing or ripping of the earth to create a course top soil roughly 1-1.3 metres in depth. These steps like terraces are called socalcos or patamares. VINEYARDS AND QUINTAS Slide8: PORT WINE PROCESSING LINE CVUT Mechanical Engineer The vineyard classification is the basis for the authorisation which regulates the amount of Port that may be produced in any one year. Taking in account the previous year’s sales and stocks of Porto held by the shippers, the Instituto do Vinho do Porto (Port Wine Institute) determines the total amount of grape that must be fortified to make Porto. The vineyard plot within the Douro is graded according twelve different physical variables. On the basis of the vineyard classification a licence would be issued permitting the grower to produce a certain amount of Port per thousand vines. VINEYARDS AND QUINTAS Slide9: PORT WINE PROCESSING LINE CVUT Mechanical Engineer PROCESS: Vindima Transportation of the grapes Crush of the grapes Fermentation prematurely arrested by the addition of aguardente (spirit) Maturation Clarification and filtration MAKING PORT Slide10: PORT WINE PROCESSING LINE CVUT Mechanical Engineer The building block of the Douro is the quinta. All the quintas have the adega (vinery), armazem (storage). - In the past, the grapes were carried out entirely by hand. Grapes were traditionally cut into large, coarse woven baskets with capacity up to 75 Kg at a time. Nowadays they are loaded on to trailers and towed to the adega by tractor. The majority of grapes are now transported to the winery in 1000 Kg steel bins known as dornas. MAKING PORT Slide11: PORT WINE PROCESSING LINE CVUT Mechanical Engineer - Baumé (a measure of the concentration of grape sugars), pH and total acidity are crucial readings but tasting grapes or juice are important for the determination of the optimum ripeness. All grapes destined for the production of Port must legally be above 11 degrees baumé. - The key to the production of a quality red Port is in the vigorous extraction of colour and flavour compounds found in the skins of the grapes. -The fermentation is prematurely arrested by the addition of grape spirit known as aguardente. MAKING PORT Slide12: PORT WINE PROCESSING LINE CVUT Mechanical Engineer The place where is extracted the colour and flavour from the Port grapes is the lagar. This is a square stone tank made from granite or cement, usually no more than a metre in depth with a capacity varying between 15 and 25 pipes (8000-14000 litres). - Over the course of a day’s picking, the lagar is filled to within 15 to 20 centimetres of the brim. - the treaders link arms and march slowly back and forth; the soles of their feet crushing the grapes gently against the stone floor of the lagar. MAKING PORT-Tradition Slide13: PORT WINE PROCESSING LINE CVUT Mechanical Engineer MAKING PORT-Tradition Depending on the temperature at which of the grapes reach the vinery, fermentation will begin quite soon after treading, possibly during the night. The action of human legs and feet helps to warm the must. Ideally the grapes will arrive at the adega registering temperature around 20ºC, rising to 28-30ºC at the height of fermentation. Slide14: PORT WINE PROCESSING LINE CVUT Mechanical Engineer MAKING PORT-Technology The process called Autovinification powered by a natural build-up of carbon dioxide in the system is the more vigorous and the most used. - After the bins has been weighed it is tipped into a reception hopper from where a large screw (‘without end’) conveys the grapes to a crusher-destemmer, which removes at least a proportion of the stalks from both red and white grapes. - Before the crushed grapes reach the fermentation tank or autovinifier, the must is dosed with sulphur dioxide at levels of between 40 and 150 mg per Kg. Most wine-maker will adjust the acidity of the must at this stage to around pH 3.6-3.7 by adding the appropriate amount of tartaric acid. Slide15: PORT WINE PROCESSING LINE CVUT Mechanical Engineer MAKING PORT-Technology Slide16: PORT WINE PROCESSING LINE CVUT Mechanical Engineer MAKING PORT-Technology The preoccupation with the ways of crush the grapes in the lagares have led to a number of attempts to simulate the gentle action of the human foot with pistons. A temperature controlled stainless steel vat equipped with programmable pistons is installed in some quintas. Slide17: PORT WINE PROCESSING LINE CVUT Mechanical Engineer MAKING PORT-Technology The basic functionality of the autovinification system: - The vat is filled of full capacity; - As the fermentation begins carbon dioxide is given off and the pressure builds up inside the tank. This forces the fermenting must up an escape valve which spills into an open holding tank on top of the vat; - Once a certain pressure has built up inside the autovinifier, the carbon escapes though a calibrated hydraulic valve. No longer supported by the pressure inside the vat, the fermenting must falls back down the central autovinification unit by force of gravity. At the same time the hydraulic valve resets itself ready for the pressure to build up and the cycle to begin again. Slide18: PORT WINE PROCESSING LINE CVUT Mechanical Engineer MAKING PORT-Technology All Port is fortified to a strength of between 19 and 22 per cent of volume. In a process called as encuba, the wine is typically run off when approximately 4 or 5 per cent of natural alcohol has been produced from the fermentation and mixed with grape spirit or aguardente in a proportion of 20 percent. The blending of aguardente is generally carried out by pumping a measured quantity of spirit into wooden, cement or stainless steel holding tank simultaneously with the free run juice. Slide19: PORT WINE PROCESSING LINE CVUT Mechanical Engineer MATURATION - All Port wines spend their first winter in the Douro. The young wines are analysed and adjusted where necessary. This provides the opportunity of the first selection and classification. - In the past days, the Port wine was transported to Porto by a boat called barco rabelo. Slide20: PORT WINE PROCESSING LINE CVUT Mechanical Engineer MATURATION - The wine matures in a loja, a shop or cellar store. Most of the wines ages in wooden vats and casks holding as much as 100 000 litres to casks of around 600 litres. They function as vessels for ageing where the permeability of the wood permits a gradual, controlled oxidation of the contents. -Wines destined for a bottling after two or tree years (Vintage) are partly aged in wooden vat and partly kept in stainless steel to preserve the primary character of the fruit. -Wines set aside to become old Tawnies are transferred to smaller lodge pipes to enhance the oxidative character of the wine. Slide21: PORT WINE PROCESSING LINE CVUT Mechanical Engineer MATURATION Slide22: PORT WINE PROCESSING LINE CVUT Mechanical Engineer RACKING - It involves the removal of clear wine from the sediment or less that have settled at the bottom of the cask or vat. Left in the wine, the less will generate off-flavours. - Ports are typically racked three times in the first year, twice in the second and annually thereafter. In the case of old wines, pipes or casks are decanted progressively, starting from the top row. Slide23: PORT WINE PROCESSING LINE CVUT Mechanical Engineer CLARIFICATION AND FILTRATION Racking alone is sufficient to eliminate heavier insoluble particles from a young Port but is does not remove unstable material found in solution that could precipitate after the wine has been bottled. Most wines are therefore clarified using fining agents like gelatine, betonite, egg white and casein. Slide24: PORT WINE PROCESSING LINE CVUT Mechanical Engineer QUALITY CONTROL The Port Wine Institute has a well-equipped laboratory and offers its services to smaller shippers. The Institute also has its rigorous quality control producers but a number of smaller shippers without their own laboratories are still sitting on a potential bacterial time bomb. Slide25: PORT WINE PROCESSING LINE CVUT Mechanical Engineer BASIC CLASSIFICATION - Ruby port, is matured for around three years in the cask and then bottled ready for drinking. - Reserve/Vintage character ports are made from higher quality vintage style wines and are matured in the wood for between four and five years. They are smoother than Ruby port. - Late Bottled Vintage, similar to vintage character port, is a blend of higher quality wines, but the grapes must all come from the specified year. By law it has to spend four to six years in wood before it is bottled; Slide26: PORT WINE PROCESSING LINE CVUT Mechanical Engineer BASIC CLASSIFICATION Vintage Port is the wine of a single year, which is bottled between 22 and 31 months after the harvest and then matures in the bottle for a minimum of ten years. - White port is made only from white grapes. It can be either dry or sweet and is at its best when served chilled.