Tawny Port is a ubiquitous style of fortified wine that takes its name from its amber-brown (tawny) color. It is lighter than Vintage Port and Ruby Port in both color and aroma. Rather than being powerful and fruit-driven, Tawny Ports tend to display oxidative characteristics (nutty aromas). Though usually considered an after-dinner drink, Tawny Port has gained increasing acceptance as an aperitif. This is particularly the case in France, by far the style's largest consumer market.
The theory behind Tawny Port is that its distinctive color, aroma and flavor come from several years' barrel-ageing. The reality is often quite different, however. Many modern Tawny Ports – particularly cheaper, mass-produced examples – are lighter in color not because of any extended ageing, but because they are made from lighter-colored base wines, using gentler vinification methods (e.g. shorter maceration time). The tawny color and nutty, aged aroma is often created by ageing in the heat of the upper Douro region, rather than shipping it downstream to Oporto as happens with other Ports. This short-cut ageing method is referred to as the 'Douro Bake', a term also used to describe the caramel-like aromas which develops in wines aged in this way.
As is the case with all vin doux naturel, fermentation of the base wine is arrested by adding high-proof grape spirit (of about 77% ABV). This lifts the wine's alcoholic strength to somewhere around 19% ABV, and kills off the yeasts. The quantity of unfermented sugar left in the must dictates the sweetness of the wine.
Tawny Ports are non-vintage wines – a blend of made from several vintages (compare this with Vintage Port and Colheita Port). Just like Sherry and non-vintage Champagne, the principle aim is to maintain the house style, rather than to reflect the vintage characteristics of any particular season.
The true spirit of Tawny Port is best embodied by Aged Tawny Port. This category covers both Reserve Tawny (which must be aged in barrel for at least seven years) and those wines bearing an age statement (10, 20, 30, or 40 years) which reflects how long they have spent in barrel. As they relate to a non-vintage wine, these age statements are necessarily vague, and increase per decade rather than per year.