Out of all the components that contribute towards the final flavor profile of whisky, yeast undeniably gets the least attention. However, it’s ironic that without these single-celled micro-organisms spelling magic, the mashed sweet ‘wort’ would have never transformed into the golden brown tipple that we heartily adore.
Yeast essentially serves as a catalyst for the fermentation process. It feeds on the sugar content of the wort to produce alcohol and another compound called congener. Congener imparts distinct flavors to the whisky.
These micro-organisms are broadly categorized into two family groups, namely wild yeast, and cultured yeast. Wild yeast by nature, is highly fragile and it only gets activated under certain climatic conditions. Irrespective of its significant aromatic potential, distillers often consider this yeast to be risky for usage considering they have no control over their growth. Cultured yeasts, on the other hand, allow the distillers to predict the alcohol content and particular aromas that add to the aromatic profile of a whiskey. Quite naturally, they are a safe bet for distillers.
Once the wort is moved to washbacks, yeast is blended within the mix to begin fermentation. Activated yeast converts the sugar content of wort to alcohol and carbonic gas, which is referred to as the wash. With time, the mixture begins to bubble and it is continuously stirred to keep the temperature within the limit.
The conversion process takes almost 40-60 hours to culminate. The resulting liquid, with an alcohol quotient of 6-8% is then decanted into storage vats called wash-chargers before being finally distilled.