In Roberto’s last blog post, we explored how each stage in our production process impacts the character of our whisky. Dozens of factors contribute to our fruit-forward flavour profile, and as you zoom in on any one aspect, a dozen more micro-factors come into view.
One of these aspects is yeast, and as part of our experimental philosophy at Nc’nean we want to explore the impact of yeast on the flavour of our new make spirit and our matured whisky. So, each year we carry out things that we call ‘yeast trials‘ - the topic of Roberto‘s blog today.
WHAT IS YEAST AND WHY IS IT USED IN WHISKY MAKING?
Yeast is a crucial ingredient in whisky making. Is a single-celled fungus and its role is to ferment sugars into alcohol. Yeast also produces flavour compounds that shape the whisky’s taste.
At Nc’nean we experiment with different yeast strains, often using strains that aren’t commonly used in whisky making - this process is called a yeast trial. In addition to creating varying flavour compounds, different yeast strains produce different alcohol yields and fermentation speeds which the distillers also have to take into account when running the trials.
Adding yeast in the fermentation stage
HOW WE DO YEAST TRIALS
We take samples of our sugary wort (the liquid which gets created during the mashing phase) and put them into ten 10-litre buckets, ensuring the sugar content in each bucket is the same.
We then add a different combination of yeasts to each bucket, including one or both of our ‘house’ yeasts (those we use in our flagship whisky recipe), plus another experimental strain. These experimental strains can range from yeasts derived from Champagne production, to yeasts specifically created for rum, beer or wine production – essentially we want to test anything which isn’t produced for whisky!
After two weeks, the yeast has turned most of the sugar in the wort to alcohol and has had time to ‘clean up’, gobbling up everything it can digest and producing characteristics specific to each strain.
Fermentation process in the washback
HUNTING FOR NEW FLAVOURS IN WHISKY MAKING
In 2024, we trialled a range of different brewing (beer) yeasts: Old English Ale, Hornindal Kveik and Hefeweizen. The Old English yeast left a fair amount of residual sugar, which in a beer would give a fuller mouthfeel, and produced notes of toffee and dark fruits. The Kveik and the Hefeweizen both worked nicely, giving us good attenuation (the amount of sugar converted to alcohol), but the flavours varied massively. While the Kveik was bursting with tropical fruit esters, the Hefeweizen leaned towards banana with a spicy, clovey background.
In the end, we just couldn’t decide, so we used both. Two weeks of full-scale production using Kveik yeast, and two weeks with the Hefeweizen. In the years to come, the casks of these whiskies will be sampled and, when ready, moat likely incorporated into our annual Huntress release, our series of whiskies dedicated to experimentation and hunting for unique flavours in whisky making
In previous years, we’ve experimented with rum yeast, red and white wine yeast, American and Belgian ale yeasts, and the list goes on…
OUR FIRST EVER YEAST TRIAL
This year’s Huntress release, Lemon Meadow, was the result of our first ever yeast trial in 2017. Here we experimented with wine yeasts: one used for Chardonnay and one derived from Champagne production. Again, both produced different flavours. The Chardonnay yeast gave notes of passionfruit and grapefruit, while the Champagne strain was buttery, biscuity and citrussy, albeit with a slightly lower alcohol yield. In the end, we opted for the Champagne yeast. The lower yield was more than compensated for by the quality of the spirit after distillation.
Comparing our flagship Organic single malt with Huntress Lemon Meadow, the results are clear. While the cask make-up of these two expressions is nearly identical, the bright lemon, biscuity notes in the Huntress contrast with the subtle stone fruits with citrus and rye bread of our flagship expression, and this difference is primarily down to the yeast. The flavours we created during fermentation persisted through distillation and maturation, all the way to the bottle.
Taste them side by side and see the difference for yourself.