For some rum aficionados, their eyes light up when seeing high-ester rum. Some Scotch whisky connoisseurs have a similar reaction when it comes to extremely peated whiskies. The higher the PPM level (phenolic parts per million), the better. But what does a whisky’s PPM level actually mean?
Remember when the Ardbeg Supernova and the first Octomore were released ten years ago? At respectively 100 and 131ppm, these smokiest of Scotch whiskies were a big step up from the usual peat levels for a heavily-peated single malt, which hovers at around 40 or 50ppm.
From that time on, PPM levels became a sort of Holy Grail for some lovers of smoky whisky. Octomore, produced at Bruichladdich distillery, ran with this newest of obsessions, culminating in the Octomore Masterclass 08.3 Edition. Released late last year, it measured in at 309ppm. A brilliant marketing tool.
But does it actually mean this Octomore is six times as peaty as your average Laphroaig or Ardbeg? Before we can answer that question, there’s a little more you need to know about peat in general. Why is it used in the whisky making process? And how does it impart those unmistakable smoky, peaty flavors into Scotch whisky?
The Good Old Days
Nowadays, peated whisky is mostly associated with Islay, however, peat was traditionally used in the whisky making process across the whole of Scotland. It was crucial to Scotland’s early distillers in the 19th century. That changed when, during the 20th century, more affordable fuels became available, like coal, gas and oil.
As a consequence, the use of peat became more exclusive to regions where those alternatives weren’t as readily available, such as on Islay, of course, but also in Campbeltown and in other remote spots like Skye and Orkney. In modern times, these distillers have alternative fuels, but still (in most cases) choose to use peat to give their whisky its traditional flavor.
Former Bruichladdich General Manager Duncan McGillivray cutting peat / Photo Credit: Bruichladdich
Decaying Plants
Simply put, peat is an organic fuel consisting of spongy material, which is formed by partial decomposition of mainly plants, like heather, grasses, mosses or trees. Peat is formed in bogs, and because of these wet conditions, there isn’t an adequate amount of oxygen for the plants to fully decompose.
Layer after layer of decayed plants are pressed and transformed into peat. Actually, the formation of peat is the first of many steps in the formation of brown coal—usually reached at depths ranging from a few hundred to over one thousand feet.
Kilning Malted Barley
When making whisky, the barley needs to germinate to develop enzymes. These are required to transform the grain’s starches into various types of sugar, which in turn are needed for the production of alcohol. After about five days, the germination needs to be stopped by heating or drying the malt, which is where peat comes into play.
Traditionally, the barley is dried inside a kiln. This pagoda-roofed building has a perforated drying floor, upon which the still wet malt is spread. Below it is a fire. Peat is added to the fire at the start of this kilning process, when the malt is still moist enough to make the peat smoke stick to its surface.
The peat kiln at Laphroaig / Photo Credit: Laphroaig
Measuring PPM
At this point in whisky production, the phenol levels in the malted barley are measured. Phenols are the chemical compounds within the peat smoke that are responsible for the smoky aromas and flavors that peat heads have come to love and expect. These are expressed as phenolic parts per million, or PPM.
Now you might think it’s logical to assume this is the most exact way to measure and express how smoky a whisky is. However, you’d be wrong do to so. Throughout the steps that follow after the kilning process—like mashing, milling, fermentation and maturation—phenols are lost.
One of the best examples is the difference between Lagavulin and Caol Ila. Both distilleries use the same type of peated barley, buying it from Port Ellen Maltings on Islay. But after going through the entire distillation and maturation process, they display a very different type of smokiness.
anCnoc Tries Something New
A more fair way of communicating the smokiness of a whisky would be to measure the liquid in the bottle. This is exactly what was done for anCnoc, a whisky produced at Knockdhu distillery in Speyside. For expressions like the anCnoc Rutter, Flaughter and Tushkar, the distillery opted to tell consumers about the PPM level after distillation and maturation.
The Flaughter for example, clocked in at 14.8ppm, which suggests a moderately peated whisky. In reality it is much peatier than you’d expect. Sadly, at Knockdhu they concluded that, while more fair, measuring PPM levels in the final liquid was too confusing for consumers. So they reverted back to the industry standard and once again mention the PPM level of the barley on their labels, not of the whisky itself.
anCnoc Cutter / Photo Credit: Jordan Wiegman
Terroir of Peat
Is there more? Yes, there is. The terroir of peat is important. Peat that is cut from a bog somewhere in Speyside has a very different composition compared to peat that originates from somewhere on Orkney or Islay. While research is not yet conclusive, it would not be surprising if different peat has a different influence on the barley.
It is also important to understand that there is not one type of phenol. Certain types of phenols might be more smoky and meaty, while others impart more medicinal and sweet aromas. A PPM reading, whether from the malted barley or the whisky, does not discern between different sorts of phenols.
What does it all mean?
In an ideal world, peated whiskies would include the phenol reading from both the barley and the spirit on their labels. Most likely we won’t ever see this become the standard, but maybe some forward-thinking distilleries will make the effort.
But even if we’d have that kind of detailed information, don’t forget those phenol types. Because of them, two whiskies measured at the same PPM level will vary in flavor profile and smokiness. For example, one might have more of those sweet and medicinal phenols than the other.
We’d have to have scientific level details to truly compare the smokiness of a whisky. But that would take all the fun out of whisky itself. Most of all, drinking whisky should be an emotional journey. Perception of flavors, and therefore of smokiness, is very personal. No matter how convenient it would be for marketing departments, it’s something that can’t possible be quantified by PPM levels.
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