In our last blog post we talked about why malt barley is more than just single malt namesake but a key flavour driver following on from that today we’ll be moving onto a component close to our hearts here at Deviant Distillery – Peat

At Deviant, we love peat. The deep, earthy, smoky aroma it brings to whisky is something special, it’s wild, primal, and unmistakably tied to the land it comes from. Peated whiskies have long held a place in our hearts and glasses, and while most people think of Scottish peat bogs when they picture smoky whisky, the story of peat and how it shapes flavour is more nuanced than that.

So what exactly is peat?

In simplest terms, peat is about half way between plant and coal.  It’s compacted plant matter formed over centuries or longer in waterlogged, low-oxygen environments.  Mosses, sedges, heathers and other plants, even kelp partially decompose and compress into an organic fuel rich in phenolic (smoky) compounds.  When peat smoke is used to dry malted barley, these phenols bind to the grain, giving whisky its signature smoky, medicinal, earthy, and sometimes even floral notes.

Peat Goes Global

Historically, Scottish distilleries used local peat because for all areas of production it was the fuel at hand, particularly on Islay where peat has become synonymous with whisky, baking regional character into the spirit.  Today, craft distilleries source peat from various sources including their own backyards for it’s unique flavour profiles: Tasmanian bogs shaped by fern and eucalypt; New Zealand bogs influenced by mānuka and native grasses. Those botanical inputs shift phenolic composition and, as we’ve found, aren’t just flavour additives, they can also significantly nudge the fermentation chemistry.

We Did the Science

Our Head Distiller asked a simple question during his recent Honours research project:
Does peat origin change more than aroma, does it change fermentation itself?

And then he did the science. Using GC–MS, an electronic tongue, and human sensory analysis, he explored how malted barley peated with different sources of peat behaves during fermentation and how those differences cascade into the resulting spirit chemistry.

The findings were fascinating. Under identical fermentation conditions, malt peated with Gladfield’s New Zealand peat produced a higher pH (less acidic) fermentation than malt peated with Simpsons’ UK peat, which showed lower pH values.

That difference in acidity had measurable consequences for flavour chemistry:

• Higher-pH NZ peat fermentations supported greater formation of long-chain ethyl esters—compounds responsible for waxy, oily mouthfeel and subtle fruity sweetness.
• Lower-pH UK peat fermentations produced fewer long-chain esters, yielding a leaner, sharper spirit profile.

This pattern suggests that peat doesn’t just flavour the malt, it influences the fermentation environment itself, possibly through mineral and organic carryover from the peat smoke although the mechanism is yet to be explored. The result is a kind of “peat terroir” that operates not only through phenolic smoke chemistry but through yeast metabolism and ester formation as well.

In the (hopefully not too distant) future, this discovery will form the basis of a future PhD chapter, expanding on how peat origin alters fermentation chemistry and the sensory structure of whisky.  But for now, it helps us appreciate that peat’s influence is more than the sum of its smoky parts.  As more craft distilleries experiment with local peat, we’ll continue to uncover these subtle and fascinating effects that connect soil, smoke, yeast, and spirit in ways we’re only beginning to understand.

What It Means for Whisky

Peat isn’t just a smoke switch; it’s a process variable. Differences in mineral/organic composition and smoke chemistry appear to modulate fermentation pH, which in turn shapes ester balance. Practically:

• NZ peat → rounder, oilier texture with elevated long-chain esters.
• UK peat → cleaner, tighter palate with fewer long-chain esters, letting smoke and shorter esters speak more clearly.

That’s peat terroir in action, from bog ecology to congener profile.

Final Thoughts

We’ve always known peat defines aroma. Now we know it can steer fermentation chemistry too. As more distillers work with local peat, expect regional peat signatures to show up not just in the smoke on the nose, but in the texture and fruit/oil balance on the palate. That’s the kind of nuance we’re here for: whisky that tells the story of place, from soil and flora to fermentation and still.