Owing to the alcohol added to the must after only a few days of fermentation, port wines are sweet; however, with the exception of white port, they are not classified by sugar residue. The main categories are: White – Ranging from dry to very sweet; by maturing in wood for longer, they acquire darker hues. Ruby – Matured in large wooden or concrete barrels; an exceptionally fresh and fruity wine. Tawny – The wine is first matured in large wooden barrels; it is then further matured in smaller ones, where it partially oxidises and acquires a spicy taste. LBV (Late Bottled Vintage) – A wine suitable for vintage, but which matures longer in wooden barrels. Colheita – Aged wine, tended for at least 7 years in barriques. Vintage – Wine belonging to only exceptional vintages; it is bottled after maturing for two years in wood and can then be aged for a hundred years or more.