The whiskey making industry has been abuzz with speculation about the next ground-breaking innovation (no terroir pun intended…). From tinkering with wood and maturation, to experimenting with climate, terroir and unusual and historic mash bills, there has been a plethora of discussions and debates. Surprisingly, one area that has garnered less attention but has great potential is the use of different strains of yeast. It’s fascinating how yeast can significantly alter the alcohol content, produce unique flavour profiles, and even impact fermentation times. Despite these significant qualities, yeast has not been explored to its full potential in the spirit-making process.

It’s about to get geeky…Did you know that there are more than 1,500 species of single-celled fungi, commonly known as yeast? Yet, for over six centuries, the preferred strain among distillers has been Saccharomyces Cerevisiae. This particular strain has earned its place in history for its remarkable ability to consume the vast majority of the sugars produced during fermentation, resulting in maximum alcohol yield. Fermentation itself is a crucial stage in the whiskey-making process, and one of its most significant by-products (aside from ethanol) is the formation of esters and congeners.

These esters and congeners may be present in small quantities, but they are responsible for imparting the vast majority of whiskey’s distinctive flavours. It’s extraordinary how much impact a relatively small amount of these can have on the final product. In fact, it’s hard to overstate the importance of yeast in the distillation process; it’s even enshrined in Scottish Whiskey law as one of the only three ingredients allowed to make whiskey. It’s surprising that such a crucial component has not received more attention.

Brendan Carty of Killowen is a true expert in this field, and he never fails to remind us of the incredible role that the Maillard reaction plays in the whiskey-making process. This fascinating chemical process is responsible for producing a wide range of compounds, including furfurals and pyrazines, from the reaction between amino acids and reducing sugars during fermentation.

There have been experiments in the past; Glenmorangie’s ‘Allta’ is proof of that. The ‘Allta’ is thought to be the first discovery and implementation of a new strain of yeast; Saccharomyces Diaemath which had been said to impart new and bold aromas to the spirit of Glenmorangie. Even when we spoke to Michael O’Boyle of Baoilleach, he was keen to stress the importance of yeast: he had tried 10-15 different strains to perfect his very own spirit after realising its impact.

Introducing the Killowen Triail (Irish for experiment, but also a clever take on ‘tri’ for three) – an innovative experiment that focuses on the impact of yeast on poitín flavour. By keeping mash bill, fermentations, distillation cuts, and ABV consistent, the only variable in this controlled experiment is the type of yeast used. This unique and interactive process allows whiskey lovers to become part of a live experiment and experience the full flavour spectrum of this poitín. Each box is accompanied by a sensory card, designed to capture the nuances and complexities of the poitín’s flavours. Once you’ve savoured every sip, you’ll be invited to participate in a live online meeting to share your findings and contribute to this exciting experiment. Interestingly, two of the three bottles use the ‘Hornindal’ and ‘Voss Kveik’ of the Norwegian Kveik Saccharomyces Cerevisiae yeast with the third type unnamed, giving the consumer a unique opportunity to name it.

Killowen uses yeast strains from WHC Labs, known for their exceptional Saccharomyces Cerevisiae varieties with high flocculation rates and impressive attenuation abilities. Notably, the strain used by Killowen boasts a remarkable thermotolerance, enabling it to thrive even in temperatures exceeding 40°C.

An additional noteworthy aspect to consider is the mash bill composition, consisting of an even split of wheat and malted barley. This unique blend is a departure from Killowen’s usual offerings and promises to lend an intriguing element to this experiment, particularly due to the relatively high wheat content.

Killowen ‘Hornindal’ Yeast Strain. ‘I’

ABV: 60%

Price: Unable to purchase individually – they come as part of trio, exclusive to the Friends of Irish Whiskey Facebook group. £75

Nose: Upon first nosing, this poitín exudes a remarkable freshness that instantly tantalises the senses. Its aroma is a delightful blend of floral and earthy notes, with just a hint of spice. Notes of aniseed and peppermint complement it, while the earthiness is evocative of damp moss, bark, and newly turned soil. As you delve deeper into the poitín, a lovely fruity sweetness emerges, with notes of grapefruit, orange peel, and lemon zest rounding out the aroma.

Palate: As the poitín touches your lips, its texture envelops your entire mouth, leaving you in awe. The viscosity of the liquid is unparalleled, with a luscious, oily quality that is both comforting and indulgent. The spicy notes take centre stage, bursting onto the palate with a delightful medley of cinnamon, clove, peppermint, and pepper, all of which is complemented by the subtle hint of aniseed. The texture continues to be velvety smooth and evolves into a rich, dark chocolate sensation. Amidst the spice and chocolate, you’ll also detect a delightful citrus note, with lemon zest playing a prominent role in the flavour profile.

Finish: It generates a remarkable warmth that spreads throughout your mouth and throat. Amidst the warmth, you’ll detect a subtle yet distinct flavour of chocolate ginger snaps, adding a touch of indulgence to the experience. The taste of Terry’s Chocolate Orange also makes an appearance, infusing the poitín with a delightful sweetness that’s both decadent and satisfying. The flavour profile culminates in a final peppery kick, rounding out the taste experience and leaving a pleasantly spicy aftertaste.

Score: 6.5/10

Killowen ‘Voss Kveik’ Yeast Strain. ‘II’

ABV: 60%

Price: Unable to purchase individually – they come as part of trio, exclusive to the Friends of Irish Whiskey Facebook group. £75

Nose: Exhibits a refined and understated quality that is both elegant and less obtrusive than ‘I’. Despite its subdued presence, the freshness of the aromas is undeniable, evoking the invigorating scent of freshly cut grass with a delicate hint of aniseed that adds to its complexity. The liquid also offers a subtle earthiness reminiscent of the rain, lending it a natural and authentic character. The ester-y notes contribute to the spirit’s sophisticated notes, revealing a hint of sweetness that is beautifully balanced with the crisp flavours of fresh honey and orange peel.

Palate: The liquid showcases two distinct elements, each one asserting itself in its own unique way. The first is a gradual emergence of spice, revealing notes of menthol and clove that build in intensity with each sip. As the spice begins to fade, a second wave of flavour emerges, characterised by a delightful sweetness that’s both nuanced and complex. The taste of honey is prevalent, complemented by the bright and zesty flavours of navel orange peel. The sweetness is tempered by a hint of bitterness that evokes the creamy, velvety taste of cocoa, resulting in a harmonious and satisfying balance of flavours. The texture of the poitín is equally impressive, filling the mouth with a luxurious, viscous quality that’s creamy and decadent.

Finish: The finish is characterised by a delightful sweetness, with a noticeable reduction in the spiciness that was present in ‘I’. The dominant flavour in the finish is chocolate, which is more pronounced than before, and creates a pleasing, indulgent sensation on the palate. The finish is rounded off by a subtle yet refreshing hint of peppermint, bringing a satisfying close to the finish.

Score: 7/10

Killowen ‘????????????????’ Yeast Strain. ‘III’

ABV: 60%

Price: Unable to purchase individually – they come as part of trio, exclusive to the Friends of Irish Whiskey Facebook group. £75

Nose: This is a more distinctive and richer aroma, with the scent of burnt caramel taking centre stage, creating an indulgent experience. Accompanying this sweetness is a lovely biscuity note, with a cereal-like quality that adds a layer of complexity to the poitín’s aroma. The notes of spice are more subdued than in ‘I’ and ‘II’ but are still noticeable. The poitín’s earthy undertones are also present, with hints of wet moss and freshly turned soil adding to its natural character.

Palate: The spice in this poitín is particularly prominent and impactful, setting it apart from other offerings. A complex blend of flavours such as menthol, clove, aniseed, and cardamom create a powerful and characterful taste profile, with each flavour contributing its unique qualities to the overall experience. While the intensity of the spice might be overwhelming to some, it is undeniably impressive and memorable. The sweetness in this poitín is also notable, with the bright citrus notes of orange peel and lemon shining through, adding a delightful contrast to the bold spice flavours.

Finish: Of the three poitíns, this one boasts the strongest finish, leaving a lasting impression. The flavour profile leans heavily towards spice, with notes of cinnamon and clove dominating the experience. While the menthol notes are less pronounced in this whiskey, the spice generates a pleasant prickly sensation on the tongue, reminiscent of chili dark chocolate. There’s an increased presence of aniseed on the finish, adding a unique touch to the whiskey’s overall character. Despite the bold flavours and spicy heat, this poitín remains approachable and enjoyable.

Score: 7/10

Conclusion

Overall, the experiment was a highly enjoyable and enlightening experience. I can confidently say that there were subtle, yet noticeable changes in the poitín’s character that can only be attributed to the use of different yeast strains. While all three poitíns shared similar flavour notes, each one exhibited them to a varying degree. However, it was the third poitín that truly stood out for me, revealing new and unexpected notes, and showcasing a greater depth and complexity than the others. This experiment clearly demonstrates the impact that yeast can have on the flavour profile of poitín and whiskey alike and underscores the importance of choosing the right yeast strain to achieve a desired flavour outcome. Brendan’s dedication to his craft and his ability to carefully select yeast strains to influence the taste of his spirits is truly impressive, and his efforts have resulted in a range of exceptional poitíns and whiskeys.

In my opinion, ‘I’ showcased an abundance of spice and earthy undertones, reminiscent of a classic poitín. It had a beautiful texture and subtle hints of fruit that added a delightful twist to the flavour profile. On the other hand, ‘II’ placed more of an emphasis on sweeter notes, with a delightful introduction of honey that provided a well-rounded taste. However, it lacked the complexity and depth that ‘III’ showcased. ‘III’ was undoubtedly distinct, with new notes and an overall greater complexity that gave it an edge over both ‘I’ and ‘II’.

To summarise, the impact of yeast on the flavour profile, texture, complexity, and overall character of a spirit is fascinating and significant, as demonstrated by Brendan’s experiment. The differences between the three poitíns were subtle yet noteworthy, highlighting the importance of yeast selection in distillation. As a whiskey blogger, I applaud Brendan’s approach and encourage other distillers to explore the potential of different yeast strains in creating unique flavour profiles. Who knows what exciting flavours they may uncover?