What is Fortified Wine?

Fortifying wines - adding alcohol, usually grape spirit, to them - is another way of making them sweet. The alcohol incapacitates the yeasts, leaving unfermented sugar.

Occasionally, the alcohol is added before the grape juice even starts to ferment, the best-known example being the Cognac region's Pineau de Charentes. Usually, it's added part way through fermentation. France's vins doux naturels, such as Muscat de Beaumes-de-Venise, Rivesaltes, and Banyuls, are made in this way, as are port, Madeira, Marsala, and Mala Sherry and Montilla differ in that fortification takes place after fermentation, which means that they begin as dry wines, although they may be sweetened afterward.

Sherry
Fortification is only one aspect of the great fortified wines. The other essential and distinguishing element is maturation. Sherry is aged through a "solera" system of fractional, or serial, blending: as it ages, each row of barrels has sherry from the next, younger, row blended into it. This constantly "refreshes" the maturing sherry. As a very rough average, on each occasion a quarter to a third of each barrel is moved to the next stage. Some solera systems date back more than a century.

The other distinctive feature of sherry is flor, a yeast that grows : layer on the surface of the young wine. If the growth is vigorous (looking rather like porridge), the wine will be classified as a fino (or manzanilla) and only lightly fortified. If there is little or no flor, the wine will be fortified more strongly and will be classified as an oloroso. The other sherry styles, such as amontillado and palo cortado, fall between fino/manzanilla and oloroso.

Medeira
Madeira has an equally distinctive but entirely different aging process. It is either heated in large tanks for about six months (the estufagem process), or it is aged in warehouses at the ambient temperature. This varies from about 66-76¡ã F (18-25¡ã C) through the year and is considerably warmer than is advisable for other wines. The effect, either way, is to give Madeira its characteristic burnt tang and to make the wine incredibly long-lived, if not virtually indestructible.

Port
Port is aged more conventionally, but in two different ways. Tawny or wood ports are aged for many years in barrels and are ready to drink when bottled and sold. Vintage, single-quinta, and vintage-type ports are aged for a much shorter time in barrel and then need to finish their development in bottle. In the case of true vintage port, this may take decades.