Fortification: Grape Spirit (Aguardente) Added Mid-Fermentation

The IVDP writes that during the 17th century vinho generoso, already fortified to survive the voyages, grew in importance as an export, and that 1678 is a key date because it is the first customs record to call the wine 'vinho do Porto'. It adds that with the signing of a treaty in 1703, which the IVDP page calls the 'tratado de Metween', Portuguese wines benefited from lower tariffs in the British market. Between the mid-17th and the 18th century, spirit was added at the end of fermentation or before transport, which gave alcoholic but dry wines; only from the 19th century was the spirit added midway through fermentation, preserving the grape's natural sugar and making the sweet wine known today. On 10 September 1756 the Companhia Geral da Agricultura das Vinhas do Alto Douro was created, and the Pombaline demarcations of 1757 to 1761 were the first demarcation of the Douro wine region. In France, the INAO specification for Rivesaltes credits Arnau de Vilanova (1238-1311) with inventing mutage, which stops fermentation by adding alcohol to fermenting wine.

• The IVDP describes the change from a dry Port, fortified at the end of fermentation to withstand shipping, to a sweet Port with the spirit added during fermentation as most probably gradual, in the first quarter of the 19th century
• The IVDP says the Douro Demarcated Region is considered the world's first denomination of origin, because a regulating body was created for a product from a specific area
• The Rivesaltes specification says neutral alcohol replaced eau-de-vie for mutage in order to preserve the wine's aromas

The IVDP describes the Douro Demarcated Region as covering about 250,000 hectares in the Douro River basin in northeast Portugal, divided into three sub-regions: the Lower Corgo (Baixo Corgo), the Upper Corgo (Cima Corgo) and the Upper Douro. Its sub-region table, as published on the IVDP site in 2026, lists 13,204 ha under vines in the Lower Corgo, 20,427 ha in the Upper Corgo and 10,177 ha in the Upper Douro, 43,808 ha in all. The Marão and Montemuro mountains protect the region from the humid west winds from the Atlantic, giving very cold winters and hot, dry summers. Most of the region, particularly along the Douro River and its tributaries, is schistose with some granite around the edges.

• The IVDP relates Port quality directly to the ideal ripeness of the grapes for the type of wine they will make, and at the winery the bunches are separated according to the categories of wine the producer intends to make
• According to the IVDP, the schistose topsoil lets water seep down to the vine roots and holds the heat from the sun, and it contains little organic matter (1.5%)
• Red Ports are normally made from riper grapes, while white grapes for White Port are, as a rule, harvested earlier than red grapes (IVDP)

The IVDP divides Port into two major categories according to the manner in which they are aged. Ruby-style wines, in which the winemaker restrains the evolution of the deep red colour and keeps the fruit and strength of a young wine, include Ruby, Reserve, Late Bottled Vintage (LBV) and Vintage; Tawny-style wines, blended from wines aged for different lengths of time in casks or vats, include Tawny, Tawny Reserve, Tawny with an Indication of Age and Colheita. According to the IVDP, large-capacity vats (tonéis and balseiros), which give reductive ageing with limited oxygen contact, are ideal for Ruby-style wines, while pipas averaging 550 litres, whose greater micro-oxygenation develops nutty and caramelised notes, are ideal for Tawny-style wines. Madeira is fortified by stopping fermentation with wine alcohol at 96% vol. and is then aged by estufagem, in stainless steel tanks heated to 45 to 50°C for no less than 3 months, or by canteiro, in casks usually on the upper floors of the lodges, where temperatures are higher, for a minimum of 2 years (IVBAM). In Rivesaltes, a French vin doux naturel, the must is muted during fermentation with neutral wine alcohol of at least 96% vol., at 5% to 10% of the must volume in pure alcohol (INAO).

• Vintage Port comes from a single year's harvest and is bottled two to three years after the vintage, then develops in bottle (IVDP); Taylor's writes that Vintage Port is kept in wood for only twenty months or so
• Late Bottled Vintage is a Ruby Port from a single year, bottled after ageing for four to six years in wood (IVDP); Taylor's says it first launched the style in 1970 with its Late Bottled Vintage 1965
• Tawny with an Indication of Age is released as 10, 20, 30 and 40 years old, and Colheita is a single-vintage Tawny aged in cask for a minimum of seven years (IVDP)
• Wines fortified to 15% vol. can grow the flor yeast film for fino and manzanilla, while above 17% vol. biological activity cannot be sustained and the wine ages oxidatively as oloroso (Consejo Regulador)

The IVDP describes Port as a fortified wine, as defined in EU legislation, produced in the Douro Demarcated Region. The Porto rules make it mandatory to use grape spirit (aguardente vínica) approved by the IVDP under Regulation 84/2010, with a strength of 77.0 ± 0.5% vol. at 20°C, and the maximum quantity used to fortify musts and blends is set each year in the harvest communiqué. The halted fermentation must leave the wine with at least 17.5 g/L of sugar. The IVDP describes this spirit as of high purity and sensorially neutral. At international level, the OIV defines liqueur wine as having an acquired alcoholic strength from 15% to 22%, made from grape musts (including partially fermented grape musts) and/or wine with added distillates, spirits and alcohol of vitivinicultural origin. Sherry is fortified after fermentation, once the new wines have been separated from their solids and given a first classification by the tasters (Consejo Regulador).

• The Porto PDO technical file states that fermentation continues until the unfermented sugar gives the wine the desired sweetness, after which the must-wine is separated and fermentation is interrupted by adding spirit
• Vintage (after 2 years), LBV (after 4 to 6 years) and Crusted are bottled early and age in bottle (IVDP); Crusted must be kept in bottle for at least three years before being sold
• Madeira estufagem wines may not be bottled and sold before 31 October of the second year after the harvest, and canteiro wines may be sold only after at least 3 years, counted from 1 January of the year after the harvest (IVBAM)
• Rivesaltes mutage must be carried out before 31 December of the harvest year, with top-up additions allowed up to a total of 10% pure alcohol before the claim declaration (INAO)

Taylor's was founded in 1692 by Job Bearsley and says it has remained independent since. Graham's was founded in 1820 by brothers William and John Graham; its site says the house acquired Quinta dos Malvedos in 1890 and that Andrew James Symington's grandsons acquired the company from the Graham family in 1970. Graham's makes its finest ports each year at its winery at Quinta dos Malvedos. On Madeira, John Blandy founded his business as a wine shipper and general trader in 1811 with his brothers Thomas and George, and Blandy's says the family is the only one of the original founders of the Madeira wine trade that still owns and manages its original wine company.

• Blandy's uses the canteiro method, in American oak casks in the warm attics of the lodge, for wines of superior quality, and the estufagem method, in which the winemaker controls the heating temperature during ageing
• Chris Blandy, the seventh generation of the Blandy family, is Chairman of Blandy's, having been CEO between 2011 and 2025 (Blandy's site, 2026)
• In 1989 the Blandys offered the Symington family a partnership in the Madeira Wine Company, which Blandy's says continues today
• Taylor's describes LBV as developed as a high quality but more affordable and immediately drinkable alternative to Vintage Port

In 2001 UNESCO listed the Alto Douro wine region as World Heritage, as an evolving, living cultural landscape (IVDP). In spring, after the first selection and blending, the winemaker decides whether a Port will be aged in the Douro or downriver in the Vila Nova de Gaia bonded lodges (IVDP). Taylor's historic cellars in Vila Nova de Gaia offer a self-paced visit that finishes with a Port wine tasting, and Graham's Lodge offers guided tours with Port tastings. On Madeira, Blandy's says its Wine Lodges, some of the oldest on the island, have a layout, shape and structure that create temperature and humidity conditions from the cellar to the attics that make them perfect for ageing Madeira wine.

• The Douro harvest begins each year between the end of August and mid-October, and picking is generally done by hand because the region's rugged terrain makes mechanisation very difficult (IVDP)
• Graham's Lodge also offers visits with lunch or dinner at its Vinum Restaurant

Primary sources (the IVDP, IVBAM, the Consejo Regulador of Jerez, the INAO, the OIV, and producers' own sites for their own facts): https://www.ivdp.pt/en/wines/port-wines/the-winemaking/, https://www.ivdp.pt/pt/vinhos/vinhos-do-porto/vinificacao/, https://www.ivdp.pt/media/pnwe55km/pdo-pt-a1540-porto.pdf, https://www.ivdp.pt/en/wines/port-wines/introduction/, https://www.ivdp.pt/en/wines/port-wines/special-categories/, https://www.ivdp.pt/en/viticulture/region/characteristics-of-the-region/, https://www.ivdp.pt/pt/vinhos/vinhos-do-porto/historia/, https://www.ivdp.pt/pt/vinhos/vinhos-do-porto/marcos-historicos/, https://vinhomadeira.com/o-vinho-madeira/vinificacao-e-envelhecimento, https://www.sherry.wine/sherry-wine/production/fortification, https://extranet.inao.gouv.fr/fichier/PNO2022AOPRivesaltes.pdf, https://www.oiv.int/public/medias/7713/en-oiv-code-2021.pdf, https://blandys.com/en/about-us/, https://blandys.com/en/about-madeira-wine/, https://www.taylor.pt/en/about/our-history, https://www.taylor.pt/en/port-wine/late-bottled-vintage, https://www.grahams-port.com/our-story, https://www.grahams-port.com/1890-lodge. Last verified 2026-09-29