Page "Fortified wine" Paragraph 7

During the fermentation process, yeast cells in the must continue to convert sugar into alcohol until the must reaches an alcohol level of 16 %– 18 %.

At this level, the alcohol becomes toxic to the yeast and kills it.

If fermentation is allowed to run to completion, the resulting wine will ( in most cases ) be low in sugar and will be considered a dry wine.

The earlier in the fermentation process that alcohol is added, the sweeter the resulting wine will be.

For drier fortified wine styles, such as sherry, the alcohol is added shortly before or after the end of the fermentation.