Production of sweet wines

The simplest method of making a sweet wine is to add sweetness such as simple or concentrated grape must to a dry fermented wine.

Really good sweet wines, however, are produced only with the natural sugars of the grapes, which are only partly fermented leading to a clearly noticeable residual sweetness in the wine. Good examples are German and Austrian higher Prädikate such as Kabinett, Auslese or Beerenauslese. In case the Must of the grapes Hans a very high sugar content the glucose of the grapes only partly can be converted to alcohol during fermentation, because the produced alcohol in concurrence with the high sugar content of the grape must inhibits the activity of the yeasts and thus stops fermentation.

In most cases, however, the fermentation is stopped by extraneous causes. Stopping the fermentation can be done in various ways, frequently by adding sulfur dioxide to inhibit and / or to kill the yeasts or by fine filtration to remove the yeasts. Another possibility is the addition of high-percentage alcohol, which stops the fermenting activity of the yeasts. The time of the fermentation stop differs depending on the type of sweet wine. The earlier fermentation is stopped the higher is the residual sugar.

Fermentation stop with sulfur dioxide or fine filtration, also including fermentation stop due to high sugar level of must, is done in the case of sweet wines such as Sauternes, Tokaj, Spätlese and other Prädikate and also  straw wine or Vin Santo. Stopping the fermentation by means of alcohol produces types of wines such Port, Madeira, Marsala or Vin Doux Naturel.