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Wine Spectator School

Class 9: Winegrowing and Winemaking

winemaking: fermentation


Also called primary fermentation, this is the process by which yeasts convert grape sugars into alcohol to produce wine. Fermentation usually takes two days to two weeks.

The three important considerations for controlling alcoholic fermentation are:

  • Yeast Selection
  • Temperature
  • Container (oak barrel or stainless steel tank)


Yeast selection

Yeasts that naturally occur in vineyards and wineries are sometimes relied upon on to ferment the wine, because they can impart exotic nuances.

Natural Yeast
The phrase "natural yeast" or "indigenous yeast" may be found on the wine label. These yeasts, which grow naturally on the grapes in the vineyard, are not used on most wines; they are unreliable and can expire before fermentation is complete.

Cultured Yeast
The safer alternative is to purchase specific strains...

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