Is yeast the whiskey weapon that Ireland has yet to tap?

March 23, 2022

by Gary Quinn

Most whiskey producers in Ireland use standard yeast strains that deliver a standard flavour profile – but change is coming and it’s packed with flavour.

There are only three ingredients in whiskey – water, barley and yeast – so you’d imagine that whiskey makers would have exhausted all avenues of experimentation to get the very best flavour compounds from each. But, in Ireland at least, you’d be wrong where yeast is concerned. Most Irish distilleries, it turns out, use very similar combinations of yeast in all their whiskey variants. But the craft whiskey movement is waking up to this potential flavour source and some new whiskey entrants will come fully loaded with new yeast-derived flavour. 

Yeast is a powerhouse at the heart of the brewing and distilling industries. It’s a single-cell organism that can multiply at great speed and efficiency in the presence of oxygen. Once it has exhausted all the oxygen, it starts to convert sugar to alcohol – in essence, fermentation. Without it we wouldn’t have alcohol, and so, yeast has the potential to be the single most important ingredient in a distiller’s arsenal. 

Craft breweries are the biggest champions of yeast, leading experimentation and driving discoveries in flavour into countless cold glasses of beer at bars all over the world. US brewers, in particular, discovered a long time ago just how many flavours yeast can produce and how by experimenting with fermentation times and yeast strains they could create incredible flavours in their beers. Craft distilleries in the US followed suit and a whole new cohort of whisky flavours have emerged. Westland distillery, for example, a small craft producer in Seattle, puts heavy emphasis on its use of yeast as a distinguishing factor in its sweet and complex single malt whiskey to give it a distinctly US edge. 



Back in Ireland, it’s no surprise to hear that Brendan Carty, distiller and owner of Killowen Distillery in Co Down, is one of the mavericks chasing change in Irish whiskey. Killowen is a small northern distillery with big ambition and Carty has won legions of fans with his cask-finished whiskies and excellent poitín. “We’re trying to do something different all the time,” he explains, “so working with yeast is an obvious choice for us. We’ve experimented with lots of different strains but we also use wild fermentation to create hybrids. We let our mash ferment in the open air for at least 24 hours before we pitch any yeast. It’s a natural way to inject the environment into your spirit and we get different results depending on the time of year,” he says, as he describes flavours like pineapple, fruit notes, layers of citrus and how adding a specific yeast culture strain helps to achieve that. 


Brendan Carty, Distiller & Founder, Killowen Distillery


It’s not the cheapest route to flavour – it takes time and effort to find the outcome required. This goes some way to explaining why many distilleries stick with the same yeast formula again and again. “New flavours from yeast come at the expense of efficiency,” Carty explains. “Particularly when we use wild yeast or try to combine yeast strains to find a new outcome. Sometimes we’ve waited a week just to see things start to happen. We’re a small craft distillery so we can take that time but the larger producers have different demands on their schedules.”

Phillip Woodnut is head of operations at WHC Lab, a fermentation and quality control company that supplies a range of yeast products to the distilling industry, among a number of others. “We supply internationally and one of our larger markets would be Japan,” Woodnut explains.  “There’s a lot of innovation and appreciation of the role of yeast in that market – a lot more than here in Ireland,” he explains. “But that is changing. We’re working with a small number of distillers who are experimenting with different strains and running trials with new make spirits. It’s early days but it’s already very interesting.” 

WHC Lab grows over 30 different strains of yeast each month and has a selection of 10 different dry yeasts. They also supply what Brendan Carty describes as a slurry form of yeast. This is a wet yeast that is already hydrated or activated ahead of delivery and transported in cold storage to be used immediately. Each yeast product has its own flavour properties and it’s only through experimenting with different types that distillers can discover the strains that suit their ambitions best. 

“Usually we use the wild yeast for about 24 hours to kickstart the process before we pitch in with lab-made product,” Brendan Carty explains. “Then we add the WHC Lab yeast that we like. It’s this combination that produces the best results for us and gives us a flavour profile that really comes from our environment,” he explains.


Blackwater Distillery

In Waterford, US-born John Wilcox is bringing decades of yeast experience to Blackwater Distillery. The Head Distiller at this ground-breaking whiskey and gin producer is long acquainted with the power of yeast. “We’ve been doing this for a long time in the US,” he explains. “Here at Blackwater we experiment with every  component in the production cycle – cuts, blends, terroir and then, naturally, yeast. It gets to the very soul of the whiskey. It’s a move long overdue in Ireland. It’s time for people to break the iron grip on how whiskey is made.”


John Wilcox, Head Distiller, Blackwater Distillery


This summer, Wilcox will lead Blackwater in a project that will experiment with five different strains of yeast. “Now that we’re in a comfortable rhythm of production and gearing up to getting juice into bottles and onto the shelves we can turn our attention to the other factors and new innovation. Although, to be honest, for me yeast isn’t that innovative. It’s old hat back home,” he says with a laugh. “It’s partly cultural I guess, this reluctance to break with tradition or set out to introduce the unknown. But in the US it’s not just the small craft distillers. Four Roses is a big operator, but if you look at the back of their label you’ll see a series of codes and these indicate the strains of yeast they use in that bottle. They have a whole range of yeast strains that they use. It dates back to pre-civil war times and the approaches that were used then. It’s fascinating.”

“The distilleries I know of that are playing in this space are really interesting. Generally they’re tied to breweries as well so that kind of specialist focus is there. Brewers tend to be much more sensitive to the yeast but then their focus changes. They’re following the profiles that produce the beer and we’re looking at the distillate outcome.” 


Changing perception

Distillers like predictability, he explains, and we need to be able to rely on flavour outcomes so the experimentation is crucial. It’s science, he explains. Yes, it can be expensive to explore, he says, but it’s a totally controllable production process. 

Back in Co Down, Brendan Carty is also completely convinced of the flavour he is seeing in his distillate. Killowen is already well-known for the flavour that is delivered from Carty’s specialist cask finishes but he has completely switched his thinking around yeast. “Now, I would say, there is a 50:50 split between yeast and cask in terms of where our flavour comes from.” His first bottles of his own-distilled and matured whiskey will be hitting the shelves later this year and we can get to try the outcome ourselves but he is already bottled the evidence in his award-winning poitín, he says. 

It’s about changing the industry and consumer expectation, Wilcox suggests. “It’s interesting to me how effortless it is back home to try new things and how much of a fight it can be here – even just to change public perception. That’s where the future lies.”