Alcohol-fortified wines are thoses to which high-percentage alcohol has been added. This addition in former times was used primarily to make the wine longer stable and has developed primarily in warm countries. The adding of alcohol can occur at different points of time – before, during or after fermentation. By-products of the alcoholic fermentation, such as aldehydes or bouquet substances, often only develop with advancing fermentation. Their formation may be prevented and such the aroma influenced by stopping the fermentation with alcohol.
In case of Madeira, Málaga, Marsala, Port or Vin Doux Naturel, alcohol is added after some days of fermentation. That means that the yeasts die and no longer will produce alcohol out of the grape sugar and such results the higher residual sugar content of these wines. When alcohol is added to Sherry its fermentation has already finisheded. Sweet sherry is produced, with the exception of sherry made from Moscatel or Pedro Ximénez grapes, by blending dry sherry styles with sweet wine. In case of Vin de liqueur or Mistela, alcohol is added to fresh grape juice before or shortly after start of fermentation.
Besides the mentioned wines, the Commandaria from Cyprus also belongs to the alcohol-enhanced wines. It is produced from dried grapes of two indigenous grape varieties, Mavro (red) and Xynisteri (white), and still today partly is fermented in earth-buried amphorae. Its oxidative maturation lasts at least eight years.
The Greek Samos is made from Muscat Blanc à Petits Grains and is available in the versions Vin doux (addition of alcohol before fermentation), Anthemis (Vin doux matured in oak barrels) and Vin doux naturel Grand Cru (from overripe berries, fermentation stop by alcohol) and the not alcohol-fortified Samos Nectar. Sun-dried Assyrtiko, Aidani and Athiri grapes, are used to produce Vinsanto on the Greek island of Santorini. There are, in addition to the alcohol-fortified versions Vin doux and Vin doux naturel, the sweet not alcohol-fortified version Vin naturellement doux. More popularity in Greece enjoys the sweet, red Mavrodaphne from Patras, made from at least 51% of the eponymous grape variety and Mavri Korinthiaki.
The Moscatel de Setúbal is one of the best-known Portuguese wines after Madeira and port. Among the alcohol-fortified wines from overseas the two Australian Rutherglen sweet wines Rutherglen Muscat and Rutherglen Topaque are well known. For the first wine a very dark-skinned strain of Muscat Blanc is vinifyed, for the other Muscadelle.