Whisky Focus - Scientist Study How Yeast Impacts Whisky Flavours

Scientist Study How Yeast Impacts Whisky Flavours

3rd September 2019
Heriot-Watt University and the Port of Leith Distillery study the impact of yeast on Scotch whisky flavour in lab to bottle research programme.

Victoria Muir-Taylor working in the lab at Heriot-Watt University

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% ABV.

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 surprising results.

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 make spirit.

“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.

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