Fortified wines, like sparkling wines, are the result of a process beyond simple vinification.
Fortified wines are manipulated through the addition of neutral grape spirit, in order to strengthen the base wines for the purpose of added body, warmth, durability or ageworthiness. Through centuries of effort, the world’s premier fortified wine regions have developed unique regimes of production and aging; these methodologies—or manipulations of the base material—have become inextricably linked to the terroir of the wines. Port, Madeira, and Sherry represent the three great archetypes of fortified wine, yet each is utterly distinct. Sicily’s Marsala; France’s vin doux naturel; many of Greece’s PDO wines; Portugal’s Setúbal, Carcavelos, and Pico; Sherry’s close cousins Málaga, Montilla-Moriles, and Condado de Huelva; the many fading traditional styles of the Iberian peninsula—Tarragona Clásico, Rueda Dorado, etc.—and a myriad number of New World adaptations constitute the remaining stratum of fortified wine styles. Vermouth and quinquinas, fortified wines flavored by maceration with additional herbs and spices (cinchona bark is essential to the flavor of quinquinas) are properly considered aromatized wines.
There are three general methods of fortification. A wine’s fermentation may be arrested through the addition of spirit while sugars remain (as in the case of Port) or the wine may be fortified after the fermentation has concluded (as in the case of Sherry). The latter method produces a dry fortified wine, although the winemaker may restore sweetness by the addition of sweetened wine or grape syrup. The third method, in which grape must is fortified prior to fermentation, produces a mistelle rather than a fortified wine. This category was once exclusively known as vins de liq
The section on the grape varieties used for Port includes the following text: ‘For Porto, the preferred red grapes are Touriga Nacional, Touriga Francesa, Tinta Roriz, Tinta Cão, Tinta Barroca, Tinta Amarela, Tinta Francisca, Bastardo and Mourisco Tinto. They must constitute a minimum 60% of the blend.’ Any indication on where is such a blending requirement is to be found? I’m curious because I’m not finding many other references to such a requirement (it is not included on the Compendium page for the Porto DOP)–and my attempts to peruse the Caderno de Especificações and a few of its annexes (most notably Portaria nº 413/2001, de 18 de Abril) have not yet proved successful. Learning the source would also aid me greatly in understanding how Port and Portuguese wines more generally are regulated, as the Caderno de Especificações itself seems very light on the specifics of how Port must be made–suggesting such regulations reside elsewhere.
Hi Keith, thanks for all of the updates. Here's the link and those requirements seem to be current based on the IVDP's site. Portugal is challenging because, as you mention, many of the requirements are found in the Portaria. It often takes a bit of digging to sort things out.