What happens when a whisky distillery co-ferments malt with grape must?
At Starward, the answer wasn’t about chasing headlines. It was about curiosity, process confidence, and a new way to express flavour. For head distiller Carlie Dyer in particular, the goal was to see how far fermentation could go while still feeling true to what the distillery stands for.
So, when the opportunity arose to create a one-off project that played with the boundaries of whisky, she went bold.
Starward Co-Ferment: How do you build flavour from two traditions?
Starward Co-Ferment is, as the name suggests, a co-fermentation of malted barley wort and freshly pressed Cabernet Sauvignon, fermented together using a co-pitch of distiller’s and brewer’s yeast.
Let’s break that down in practical terms.
The grape juice was delivered post-crush, without skins, and added directly into Starward’s fermentation tanks alongside their usual wort. Yeast was then pitched – a combination of distiller’s and brewer’s strains – and fermentation began.
Despite early concerns around attenuation, the fermentation ran dry, producing a highly aromatic and textural wash. This hybrid liquid was then double pot distilled and matured in a mix of fresh and charred Australian red wine barrels for nearly six years.
The end result is a boundary-defying spirit (part malt, part grape) that isn’t legally whisky or brandy, but borrows character from both.
It opens with vibrant, lifted aromatics, leading with raspberry, plum and floral notes from the Cabernet Sauvignon, balanced by a soft malt base and gentle fermentation esters. To taste, it’s juicy and textural, with red fruit brightness, subtle spice, and a clean, wine-like acidity. It finishes familiar in structure, but unmistakably different in tone.
“It was never going to be a commercial release in the usual sense,” says Dyer. “But it was a really fun challenge to create something expressive that reflected our values and our processes.”
When fermentation becomes the feature
The limited-edition bottling started as a conceptual experiment, rooted in the idea of fermentation as a flavour driver. “Fermentation is a big part of what gives our spirit its character,” explains Dyer. “Doing a co-ferment felt like a natural extension of that curiosity.”
Equally, by ensuring it was matured in Starward’s signature red wine barrels, it ties the final product back to the DNA of the distillery. It speaks of their provenance, their process (across the core range) and their house style overall.
“It reflects who we are,” she says. “Wine cask influence, fermentation-led flavour, and a love for texture and generosity.”
Innovation grounded in confidence
Dyer is quick to note that while the project was creative, it wasn’t reckless. She had run small-scale fermentations at bench level, trialling different grape varietals before scaling up.
And it was that combination of lab trials and their familiarity with timings, equipment, and outcomes that helped steer the team.
Early in the process, she’d been concerned about how fermentation would unfold: “I did worry that the yeast would struggle to ferment dry all the sugars that are in the grape juice, the gravity started high, but the attenuation was pretty good.”
“I also played around with multiple varieties at a bench level, and it made sense for us to pick a red variety, given most of what we do is red wine cask,” she explains. “[More broadly] It worked because we know our system,” she says. “We didn’t change our process and ran it through our normal parameters.”
And this is key. When doing NPD, it’s very easy to start on a tangent and change every element thereafter. That wasn’t the case here – while the grape must introduced something new, the rest of the process (fermentation duration, distillation approach, and maturation method) remained consistent with what they would otherwise do.
Their clarity, and the focus on what the“innovation” part was, made the outcome more predictable, even if the input was completely unconventional.
Unexpected shifts from a familiar process
Despite running the process to their usual parameters, the introduction of grape must into the wort changed the dynamic in subtle but meaningful ways. It was always going to. “The lag phase was probably longer,” Dyer recalls. “I think the yeasts were probably figuring out, oh my god, what the hell am I doing in here?”
At the time, all of the distillery’s fermentation was allowed to run hot – reaching 30 to 33°C before chilling kicked in. “Which is crazy when you think of wine fermentation,” she adds. “You don’t want your ferment to go up that high.” Since the time of the NPD, she has implemented far tighter temperature control parameters at Starward, aiming to hold around 26°C to retain more esters and aroma. Which raises the interesting question – would have worked had it been temp restricted and the chillers kicked in at an earlier stage? Or did the co-fermentation reach it’s full potential because it was allowed to run hot? Impossible to tell…
Still, the overall production was straightforward. “We didn’t have to ferment the wine separately or keep that stable,” she says. “It didn’t go through malo, I assume, because we distilled it straight away.”
Meanwhile, on the stills, their regular cut points were maintained, and Dyer tracked 100ml fractions for detailed sensory assessment. “The grape aromatics came through earlier than what we would normally make our cut at,” she notes. That insight may shape future tweaks. “If we do more, we can experiment – move around the cuts depending on the grape variety.”
In other words, while the core process remained unchanged, the sensory opportunities – and learning – were only just beginning.
What else is possible?
Dyer points out that the creative potential of co-fermentation is far from exhausted. “I think it would be really fun to try some white grape varieties,” she says. Her early bench trials with whites revealed vastly different aromatics – some, like Muscat, were “just like perfume” and completely overpowered the malt. “But maybe in a lower ratio, it could be good,” she reflects. Riesling and Chardonnay also sit on her list of possibilities.
Alongside varietals, yeast selection is another area she’s eager to explore. “If we did more red varieties, I think it would be cool to get a yeast strain that really aims for those red fruit characters,” she says. “Our usual yeast is all banana and tropical fruits.”
That curiosity isn’t limited to flavour alone. The team has already run multiple yeast trials – part NPD, part contingency planning. “There’s a lot of really cool yeasts out there, and yeast companies have gotten really good at pinpointing specific flavour profiles.”
Her take on it all? Growth isn’t always linear.
What trials teach you about your everyday
For Dyer, one of the most valuable outcomes of innovation isn’t just the new ideas, it’s what they reveal about your existing systems and the way you understand what you do.
“A big thing I’ve learned is consistency,” she says. “Setting standards for everything we make helps massively when you’ve got so many moving parts – barrel variation, malt batches, weather fluctuations. If you have a reference to go off, it makes life a lot easier.”
That mentality informs not just new product development, but day-to-day operations. “I taste every batch of wash and spirit,” she explains. “Because if something’s not right – maybe a condenser isn’t working, or a heat exchanger’s building up char – you’ve got to pick that up before it affects the whole batch.”
In a still-young Australian whisky scene, Carlie and her team see experimentation and standard-setting not as opposites, but as two sides of the same coin. One helps raise the experience levels, and from there set a new benchmark for the everyday standard being aspired to.
It is a mindset that we should universally take note of.
“We’re all kind of learning together,” she says. And while the category is still finding its own rhythm, it’s the willingness to keep exploring (and then refining) that will help it (and everyone making) grow.
Curiosity is part of our craft, and discipline is how you harness it
For distillers looking to push their category without losing process control, this is a case study worth paying attention to. Focussed innovation. Trial-based first, scaled later. One change at a time. Everything else held steady… etc.
Projects like this are what great NPD looks like. They help improve a team’s skill set because they create a learning curve that asks the right questions – what worked, what changed, and what does that tell you about your own process?
With the benefit of hindsight, Co-Ferment now stands as more than just a creative detour for Dyer and the Starward team. It can be seen as a product that’s not just about innovation for innovation’s sake, but a moment to refine how they make decisions, test their boundaries, and understand their own process more deeply.
As more distillers look to differentiate without losing their operational footing, replicating this kind of disciplined experimentation could be a valuable exercise.
Not to create a world of hybrids. Not to push the frontier of spirit categories. But because curiosity is part of our craft and that mindset should sit at the heart of how we all build and grow.
