Heriot-Watt University and the Port of
Leith Distillery study the impact of
yeast on Scotch whisky flavour in lab to
bottle research programme.
Scotch Malt Whisky is made from malted barley, water and one other very
important ingredient which we never really hear mentioned much by the whisky
producers and that's yeast, the only organism that is allowed in whisky making.
In the past whisky makers would dismiss any idea that yeast made any
contribution to the aromas and flavours of the final whisky, they argued that
any flavours generated by yeast during the fermentation process did not make it
past the distillation process, but we know now that this would only be true if
they were distilling the fermented liquid known as "wash" to the point of
neutral alcohol which would be at least 95% ABV but they do not do this,
typically most Scotch malt whisky distilleries use a double distillation process
which takes the distilled spirit to an average alcohol strength of around 70%
Heriot-Watt University and the Port of Leith Distillery in Edinburgh are
undertaking a comprehensive examination of the impact of yeast on the flavours
found in Scotch whisky.
The study which has been funded by Innovate UK, the Knowledge Transfer
Partnership (KTP) will test more than 20 strains of yeast, one of just three
ingredients authorised in the production of Scotch whisky. As the KTP celebrates
its first-year anniversary, its participants say it has already revealed some
The project has already identified brewing strains of yeast more commonly used
for beer that possess promising characteristics for whisky production, with an
ability to maintain the balance between alcohol yields and flavour.
Victoria Muir-Taylor is the Knowledge Transfer Partnership Associate Distiller
at Port of Leith Distillery. A graduate from Heriot-Watt’s International Centre
for Brewing and Distilling, who is leading the research commented: "The
objective of the research is to determine how the choice of yeast contributes to
the complexity of flavours found in Scotch whisky.
"A huge amount of attention has been given to the type of cask used for
maturation, but we want to focus on the early phases of the production process.
We want to see what new characteristics we can bring out in a whisky from
changing the yeast alone. We believe this is a key area for innovation."
Until the mid-20th Century, many whisky distilleries shared yeast with the local
brewery or used a combination of a distiller’s yeast for alcohol and a brewer’s
yeast for flavour and mouthfeel.
Since the 1950s, the most prevalent strain of yeast used in Scotland has been M
strains of S.cerevisiae. A new super-strain, called MX, has recently been
introduced due to its quicker and more efficient impact on fermentation. Mauri,
originally from a baker’s yeast, is also still used.
Ian Stirling, co-founder of the Port of Leith Distillery, continues: "There are
hundreds of commercially available yeasts and, while not all are suitable for
whisky distillation, many can create unique and distinctive flavours in the new
“Until recently, efficiency has tended to dominate the conversation about yeast.
However, we’ve already seen a few companies conducting experiments with some
wonderful results reaching the market. However, Scotland still lags behind the
US in terms of innovation in this area.
"We have now reached the halfway point in our two-year research and development
programme, in which we are experimenting with a wide range of yeasts and
fermentations, drawing ideas from different sectors of the drinks industry. We
want to find new flavours and styles that we can draw through to our distillate.
There are a huge number of variables to consider such as how long you ferment
for and at what temperature, but we firmly believe that this research will be
beneficial for the industry as a whole."
Victoria Muir-Taylor concludes: "We will be sharing the results of this project
with the industry at large to benefit innovation and the continued growth and
development of the Scotch whisky industry. As one of Scotland’s key exports, it
is essential that we continue to push boundaries."
The Knowledge Transfer Partnership will be completed in September 2020 with the
findings made public.