How Single Malt Whisky is Made – Part 2: Fermenting

by Mike Phillips

In this second post detailing how whisky is made, we’ll discuss the next step in creating whisky: fermentation of the wort.

As a quick refresher, wort is a sugary substance that’s produced after grinding and mashing the grain ingredients for the whisky, then mixing with hot water.

Once the wort is drained into the tank, it is ready to be fermented.

Fermenting Procedure

The tank the wort is drained into is a fermentation tank called a washback, which is normally made of either stainless steel or Oregon Pine. Yeast is added to the wort and then the mixture is left to ferment. This process takes several days and produces alcohol and carbon dioxide. The carbon dioxide will create a froth at the top of the wort, which (in some distilleries) will be beaten back with mechanical beaters.

Once the fermentation process is complete, the liquid, now called wash, has an ABV of anywhere between 5% – 10% and (aside from the absence of hops) is not much different from beer.

How Variations in the Fermentation Process Affect Flavor

The water used to create the wort (ie: springwater, and where the springwater is procured from) will impact the taste of the spirit. Additionally, the amount of time the wort is fermented into wash will impact the flavoring of the spirit as well.

Step 3 of the whisky production process is distillation, a very important step that can drastically impact flavoring.

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