Which of these wines is fortified before primary fermentation is complete?
Unlike Sherry or Madeira which can be fortified before or after primary fermentation is completed, Port is fortified with neutral grape spirits (clear brandy) before fermentation is complete. Once Port grapes are crushed, the soupy mass is poured into a tank so that fermentation can begin to turn the grapes’ sugars to alcohol. About thirty-six hours into the process, when about half the natural sugar has been converted into alcohol, fermentation must be stopped. To do so, clear brandy with an alcoholic strength of 77 percent (about 150 proof) is added to the Port. The alcohol in the brandy causes the yeasts in the wine to die, and fermentation subsides. The result is a sweet wine with about 7 percent residual sugar and fortified to about 20 percent alcohol.