There are around 40 different grape varieties permitted in the production of Port - however the vast majority of Ports are produced from a blend of 5 grapes - Touriga Nacional, Touriga Francesca, Tinta Barroca, Tinta Roriz, and Tinto Cão.
Touriga Nacional produces small, dark-skinned grapes that produce opaque black wines of great extract and high tannins - it gives grip, body, and structure to the blend.
Touriga Franca has a thinner skin and consequently produces wines lighter in colour and tannins than Touriga Nacional. It contributes fruit, aroma, suppleness and roundness.
Tinta Roriz is the Portuguese name for Tempranillo and its high sugar content and low acidity contribute colour and fruit.
Tinta Barroca which is normally grown at highish altitudes and on north-facing slopes, is prized for producing wines of delicacy, finesse and with smooth, velvety fruit. It brings elegance and sweet, ripe fruit to the final blend.
Finally Tinto Cão produces fine and complex wines, though it is probably the least important of the 5 grapes as its painfully small yields have reduced plantings to almost insignificant levels.