The British governments definition of Scotch whisky is laid out in the ‘Scotch Whisky Regulations 2009’. These regulations state;
In these Regulations “Scotch Whisky” means a whisky produced in Scotland—
that has been distilled at a distillery in Scotland from water and malted barley (to which only whole grains of other cereals may be added) all of which have been—
fermented at that distillery only by the addition of yeast;
Brewers historically fermented their beer in such a way that they could harvest live excess yeast from their beer and to a certain extent, so did some grain distillers. This excess yeast was then used by malt distillers to ferment their wort. This supply, although plentiful, had its risks mostly through bacterial contamination exacerbated by long supply lines and variable strain types. This gave rise to variable performance in the distillery. In the 1960’s, the era of efficiency, consistency and bad architecture, this problem was resolved with the development of specialist yeast factories. These factories selected specific yeast strains that were very efficient in fermenting to produce alcohol from cereal. They were also able maintain the strain purity leading to consistency. This approach was mirrored by the development of different barley varieties. Efficiency and flavour are not always good bed fellows.
At InchDairnie we work with our 3M’s, the first being our Materials and yeast is one of our materials. We use many different strains of yeast throughout the year and we use both cream yeast and dry yeast. Our dry yeasts are carefully rehydrated before being added to our wort.
We use these different yeast strains to help develop different flavour profiles in our new make spirit.
Each of our seasonal InchDairnie single malt campaigns use different yeast strains in order to develop the flavour profile that matches the season that it is being distilled in. Also, we use a specific yeast strain for our grain whisky RyeLaw and our peated malt KinGlassie. Each strain works differently producing a different ester profile in the wash. These yeasts have been selected primarily for their flavour producing qualities and not their spirit yield qualities. This means that we sacrifice efficiency for flavour.
Only by creating the flavour profile in our fermentation vessels, which are located outside on the north elevation of the distillery building to keep them cool, can the flavours be captured in the stills.
Much work still needs to be done with yeasts and fermentation conditions to understand the flavour properties this will give the new spirit. So more on this matter in the years to come
InchDairnie Distillery Managing Director