the red wines tend to be very tannic due to prolonged periods of maceration during winemaking. many producers make liberal use of french and portuguese oak. the style has been improving, with some producers concentrating on making more fruit-forward styles with smoother tannins. historically, the white wines were known for being over-oxidized and full-bodied, but more modern winemaking has been producing white wines that are fresh, fruity and fragrant. the encruzado is the principal grape of the area's whites, with some blends of malvasia fina and bical."garrafeira" white wines require at least 0.5% more alcohol by volume than the 11.5% doc minimum and at least 6 months aging in oak. the maximum allowable yields for white wine grapes is 80 hl/ha.