A ‘ppm’ figure is a measure of phenolic compounds in ‘parts per million’. It’s often used as a second-hand way to refer to the peatiness of a whisky.
For example, Lagavulin 16 Year Old is made with malt peated to around 35 ppm. Laphroaig 10 Year Old is around 40–45 ppm. Bruichladdich’s Octomore leans into the “world’s most heavily peated” claim with malt peated to over 100 ppm, reaching a historical high of 309.1 with Octomore 8.3.
So, the more ppm a whisky has, the peatier it is. Right? Wrong. It’s not quite that simple.
Who wants to get nerdy about ppm? You? Great. Let’s get to it.
This is peat. But can you measure peat in whisky? Kinda…
Dave Broom on ppm
Let’s kick things off with some insight on ppm from whisky writer Dave Broom from his recently published The World Atlas of Whisky 3rd edition (2024).
“These figures are bandied around by some distillers, writers, and whisky lovers as if within them lies the secret of all smoky whiskies”. He does know how to set a scene, Our Dave.
“The problem is that the ppm figure quoted refers to the malted barley, and most of the phenols are lost throughout the process. Some are left in the draff (mainland cows famously refused to eat the smoky Islay draff) and in distillation. Phenols have a high boiling point, meaning that they come across late in the spirit run. Most of them end up in the feints, not the final spirit. Some phenols aren’t even detectable by the nose,” Broom continues.
He summarises, “The ppm in the spirit is a more accurate measure, but as Torabhaig’s research illustrates, it’s more to do with which branch of the phenolic family is captured. Peat isn’t peat. Smoke isn’t smoke”.
Dave Broom helps shed some light on the subject
Torabhaig’s research
I don’t know about you, but when I heard Torabhaig had done some research into this topic, I was intrigued. So I asked them about it. Here’s what Neil Macleod Mathieson, whisky maker for Mossburn and Torabhaig, had to say.
“Our interest in the chemistry of the phenolics in peated whisky stems from the fantastic nature of the human sense of smell. Our analysis found that whiskies with widely different aromatic profiles actually had remarkably similar analytical phenolic levels, even between the sub-families of phenol compounds. The layering in the initial spirit, the wood-contact during ageing and the reduction for bottling or drinking all made major changes to how each phenolic family is perceived by the consumer.”
Mathieson then decided to take a step back and understand these differences by taking the analytical route right from the first months of distillation. He found that this guided the cut and wood selection at Torabhaig, and gave insights into why and what aromas they were finding in the spirit.
Peat is at the core of Torabhaig’s character, but the distillery wanted to go deeper
Consumer clarity, perception, and peat
“We made it a point to share these findings and try to give a little clarity on the phenolic content of the final whisky – and help our consumer understand that the bigger the number does not necessarily mean the more aromatic the aroma of the whisky. In our own case, our Torabhaig peaty identity and phenolic aroma are often at odds with the number we find by analysis,” Mathieson explains.
He adds, “As we are now approaching the 10yo mark we are also seeing the increase of phenols, particularly guaiacols from Lignin breakdown in our first fill barrels, adding to the total phenols rather than maturation leading to a lessening in phenolic strength – and with reduction for bottling and drinking this will allow for more of the burnt ember and earthy aspects of guaiacol to be perceived in the flavour and smell of the whisky”.
This kind of research provides invaluable insight, and anyone else who has looked into this matter with a similar level of interest and rigour is highly encouraged to share their thoughts in the comments section below. Let’s get dialoguing, whisky nerds (said with love, always).
A whisky’s ppm can be revealing, but you do need to taste the whisky too
Why ppm can be misleading
To summarise, ppm tells you how much peat went in, not what comes out. A whisky with 55 ppm malt might taste gentler than one made from 20 PPM malt. It depends on the distillation cut, cask type, how long it’s been aged…
A good example to remember is Lagavulin and Caol Ila. Both are Diageo-owned distilleries that source peat from the Port Ellen Maltings, using malt peated to ~35 ppm. The former hits harder on the smoke because of cut points, cask selection, and the addition of tiny flakes of charred wood extracted from Nick Offerman’s moustache (OK, might have made that last one up).
The peatiness of a whisky changes with age. Peat fades in the cask. A heavily peated whisky might mellow dramatically over 20+ years, even if the malt was sky-high in PPM. Octomore often tastes more refined and fruity than you’d expect.
The Last Drop: What you taste isn’t what was measured
A whisky peated to 309.1 ppm will taste smoky, of course. But ppm isn’t a tasting note. It’s more like the number of chillies printed on a curry menu. Useful, but not the full story. You’ve still got to take a bite. Or in this case, a sip.