How Are Sweet Wines Made?

A shorter fermentation will leave more sugar in a wine. This allows for medium to fairly sweet and fruity wines. When fermentation is stopped it prevents all the sugar turning to alcohol. The yeast can be killed to stop fermentation by pumping in sulphur dioxide but too much sulphur left from this process can taint the wine with a very unpleasant flavour. Modern methods involve chilling the wine to kill the yeasts or spinning in a centrifuge which gets rid of all the solids including yeasts. Cheaper German style wines might simply resort to adding some grape juice to full fermented white wines to bring the sweetness back up to the required level. Fortified wines are sweet but produced differently. The addition of a neutral tatatng spirit both raises the alcohol level and kills off the yeasts. This method is used to produce Muscats. The most natural method is to start with the grapes. Partially drying grapes after harvest concentrates their natural sugars so that more remains after the usual fermentation. Italian Vin Santo is made by this method. Leaving grapes to be attacked by a fungus also helps concentrate the sugars and this is a method used to produce many dessert wines.