wolit (03/12/83)
In response to a recent query: Fortified wines are made by adding distilled wines to regular wines. This is necessary because, as pointed out, the yeasts responsible for the fermentation of sugar to alcohol are themselves poisoned by alcohol concentrations above 11% - 13% or so. By distillation, that is, by heating to increase the vaporization of the more volatile components -- in this case, alcohol -- and then condensing the vapors, the concentration of alcohol in the product is raised (and the character is changed, too, of course). Thus, distilled wines are to regular wines as, for instance, a malt whiskey is to beer. Distilled wines include such things as brandy and cognac. Fortified wines are such products are sherry and port.
sif (03/13/83)
Fortified wines are made by adding alcohol (usually in the form of brandy) to the fermenting must. This stops the fermentation and raises the alcohol level. If the fermentation was far from complete, the resulting wine can be both sweet and alcoholic. Thus is port made. It is true that many wine yeasts die in the 11-13% range, but there are yeast cultures that are far more tolerant of ethanol. The grape and the details of fermantation also control the degree of alcohol that the yeasts can produce. A number of California Chardonnays from 1981 are in the 15% range (and burn acordingly). Late Harvest Zinfandels routinely exceed 15% without fortification. If memory serves, David Bruce made a Late Harvest Zinfandel in 1970 that came in at 18.1%, allegedly without fortification! (The wine was wretched but interesting).