Portuguese wine regions established the denomination of origin (DOC) system when the country joined the European Union in 1986. Similar to the Spanish Denominación de Origen (DO), the DOC replaced the Região Demarcada system developed in the early 20th century.
In addition to protecting the designation of origin, the DOC also establishes regulations aimed to assure high quality standards of the wines that belong to a specific wine region. Requisites include establishing alcohol content range, defining permitted grape varieties, time for bottle or oak aging, among others. All producers are required to submit wine samples to a regulating body in order to assure compliance with DOC standards.
In addition to the DOC designation, we can also find two tiers: Indicação de Proveniência Regulamentada (IPR) and Vinho Regional. IPR is similar to DOC “in training” and designates regions that have implemented their own regulating bodies without establishing an internationally recognizable identity for their wines. Finally, Vinho regional, is the lower tier that accommodate all wines that do not fit in the higher quality groups.
References: J. Robinson (ed) “The OxfordCompanion to Wine” ; K. MacNeil “The Wine Bible” by WorkmanPublishing
by Francisco Sobral, Wine Curator