In general, fortified wines range from about 15% to above 22% in alcohol.
Dry or Sweet - Timing of the Fortification
Fortified wines can be dry (such as sherry wines) or sweet (such as port wines). The timing of the fortification (i.e. the addition of the spirit) is critical to the eventual style of the wine.
For example, all sherry wines are fermented fully dry first, before the fortification. So, sherry wines are dry. Sweet sherry wines are sweet because of a further addition of a sweetening agent, and not due to the fortification.
In contrast all port wines are sweet as the fortification occurs when the grape juice has just fermented to about 6% abv. The addition of the spirit arrests the fermentation process leaving significant residual sugar in all port wines of about 120g/l.
Madeira wines can be medium dry or very sweet, depending on when the fortification takes place. The timing of the fortification is linked to the different Madeira grape varieties. For example Madeira made from the Sercial grape Sercial is the driest style. The fortification occurs quite late in the fermentation process leaving only circa 25g/l residual sugar in the wine. In contrast Madeira made from Malmsey grapes is fortified earlier in the process, resulting in much sweeter wines with up to 120g/l residual sugar. Madeira wines made from Verdelho and Boal/Bual fall in between in terms of sweetness.
Vins Doux Naturels
Vins Doux Naturels (VDN) wines such as Muscat de Beaumes de Venise, Muscat de Rivesaltes etc are all fortified early on during the fermentation of the grape juice, resulting in wines with between 110g/l and 120g/l residual sugar. The addition of spirit in making VDN wines is known as mutage rather than fortification, but is essentially the same thing.
The spirit alcohol used for most fortified wines is grape spirit. The final alcohol level of the wine will depend on the amount of spirit added. For example, Fino sherries are fortified just to 15% abv to allow a layer of flor yeast, necessary for Fino's biological aging, to grow on the wine's surface. In contrast Oloroso sherry wines are fortified higher to 16% to prevent any flor growth so that the wines can age oxidatively, necessary for the Oloroso style.
This is not an exhaustive list of fortified wines styles. Others include Banyuls, Maury, Malaga, Rutherglen Muscat and Pineau de Charente wines.
Mary Gorman-McAdams, MW (Master of Wine), is a New York based wine educator, freelance writer and consultant.
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