Modelling Scotch Malt Whisky Fermentations and Impact of Fermentation on New-Make Spirit Character

Modelling Scotch Malt Whisky Fermentations and Impact of Fermentation on New-Make Spirit
Character

During the production of Scotch malt whisky, wort carbohydrates are fermented by Saccharomyces
cerevisiae to produce a beer-like product known as wash. This fermentation process produces a large
proportion of the key flavour congeners that exist in the matured, final product. Therefore,
fundamental understanding of fermentations is key to producing a consistent new-make spirit as well
as exploring innovation within the Scotch malt whisky category.
Modelling fermentation provides insight into various aspects of a distillery process including lag and
total fermentation time, along with original and final predicted extract values. A large dataset
containing the fermentation profile of 364 fermentations made up of 40 individual beer and whisky
brands demonstrated that the 4-parameter logistic model was the most suitable. This also further
highlighted key differences between the fermentation categories. This was true despite whisky
fermentations having significant differences from that of ale and lager.
This logistic model was then applied to fermentations at two industrial distilleries – Glenmorangie and
Ardbeg. The fermentations at Glenmorangie were determined to be consistent across the three year
monitoring period, with no significant change (p > 0.05) determined between defined models. The
Ardbeg distillery was determined to have a significantly longer lag phase when compared to
Glenmorangie and it is thought that this is due to differences in yeast format.
The modelling process was also observed in small scale laboratory experiments to investigate the
effect of wort original extract, novel yeast strains and co-fermentation with bacteria. Analytical and
sensory profiles of the new-make spirit was also assessed to determine the impact the change in
fermentation parameters had on the resulting spirit.
From the results of the laboratory experiments, the feasibility of these fermentation regimes was
determined. The resulting spirit also provided an indication of the expected changes that may occur
when employing such methods at full, industrial scale. This could be used as a tool to increase existing
product quality or develop new whisky products that are unique in style or characteristic.