This instalment of our continuing series about our organic winemaking practices follows the fruit from the vineyard through to the juice stage. In the June installment of this series about our organic winemaking practices, we dealt with the initial stages of the winemaking process, in which juice is extracted from fresh grapes. This installment introduces you to the master alchemist without whose talent the world of food and wine would be a pretty boring place. Alchemy, the transformation of one substance into another, is indeed what yeast does, because these organisms consume the natural sugars present in grape juice and produce in their place alcohol and carbon dioxide.
Yeast is naturally present as an airborne organism just about everywhere on earth.
In the right conditions, any fruit, including wine grapes, will spontaneously ferment without added yeast. However, because these wild yeast organisms are unpredictable, not very vigorous and often accompanied by less desirable bacterial companions which may overpower them and spoil the product, most winemakers rely on a cultured yeast. The key is that a particular strain, with identifiable and desirable characteristics, has been identified, isolated, cleaned up and produced in mass quantities. Think of it as the Ivy League of single-celled organisms. If fermentation doesn't start quickly, the entire batch of juice can spoil in a day.