Port wine is made from four core varietals, indigenous to Portugal. At harvest time, all picking is done by hand and each varietal is picked according to its ideal ripeness, and the fermentation of each varietal and vineyard block kept separate.Fermentation occurs in either an autovinificator or foot-trodden in a lagare. After approximately 36-48 hours when the wine reached about 8% alcohol, the must is strained off into vats with high-proof neutral grape brandy at roughly one part spirit to four parts must. This brandy halts the fermentation process by killing the yeast. The sweetness one tastes in a fortified wine is the natural grape sugar that has not been fully fermented into alcohol. The wine is then racked off into barrels for aging and future blending.