Fortification
Winemaking · Intermediate · 2 min read
Fortification is the winemaking practice of adding a distilled spirit, usually grape brandy, to a wine to raise its alcohol content and, in many cases, to stop fermentation or change the style. The result is a fortified wine, a category that includes Port, Sherry, Madeira, Marsala and Commandaria, plus a few British examples such as English pomace brandy and the new wave of UK dessert wines.
How fortification works
The most common addition is a neutral grape spirit, usually around 77 to 96 percent alcohol, made by distilling wine. The spirit is added either during fermentation (to stop it, leaving residual sugar) or after fermentation (to stabilise and concentrate the wine). The timing defines the style.
Port, for example, is fortified partway through fermentation, leaving a sweet, high-alcohol red. Sherry is fortified after fermentation, producing a dry wine that is then aged under flor. Madeira is heated and oxidised as well as fortified, giving a uniquely complex wine. The UK produces a small amount of fortified wine under specific PGI rules, mostly from grape must or imported base wine.
UK fortified wines
Fortified wine is a small but interesting niche in the UK. A few producers, including English Vine No. 1 in the Cotswolds and a handful of others, make a UK Pomace-style spirit from grape skins, marc and neutral alcohol. Some English dessert wines are made by fortifying a partially fermented must with neutral spirit, in the Port style, although volumes are tiny.
The wider UK fortified wine category is dominated by imports, particularly Port from Portugal and Sherry from Spain. These are part of the fabric of UK wine culture, and the rules governing their sale, including specific labelling requirements, are well established. The Wine and Spirit Trade Association runs the UK trade body's annual Port and Sherry tasting, which is one of the highlights of the trade calendar.
The science of fortification
Yeast dies when the alcohol concentration in a fermenting must reaches about 15 to 16 percent, depending on the strain. By adding a spirit to bring the must up to that level partway through fermentation, the winemaker stops the yeast and leaves a sweet wine with around 18 to 20 percent alcohol. By adding the spirit after fermentation, the winemaker produces a dry, fortified wine of similar strength.
The choice of spirit matters. A clean, neutral grape spirit preserves the varietal character of the base wine. A heavier, more aromatic brandy can dominate. UK producers making pomace brandy or grape spirit typically use a small copper still, often the same kind imported from Portugal or Germany, run by a craft distiller on a contract basis.