White Porto was first introduced by Taylor, Fladgate & Yeatman in the 1930s. It is produced from grapes grown in the Douro Valley. The winemaking is very similar to that of red Porto, although white Porto is fermented longer before brandy is added to stop the fermentation, leaving less residual sugar for a drier style of wine. Siroco is fermented half on the skins and half off, with no pumping-over, to minimize oxidation. The wine is then transferred to large wooden vats for four years of maturation.