PORTLAND, Ore. Nov. 2, 2016/ Troy Media/ – Peat has a long association with Scotch whisky, indelibly influencing aroma and taste.
Historically, in many parts of Scotland, peat was the only fuel available. Those whisky-producing areas of Scotland where peat has traditionally been used as a fuel, most notably Islay and the Western Isles, have long been famous for producing heavily-peated whiskies.
Peat used in kilns to dry malted barley imparts “peat reek” – a distinct, smoky, sometimes phenolic quality to the resulting spirit.
Over the last several decades, there have been two contrary trends in the use of peat. Overall, the level of peatiness in Scotch whisky has decreased. At the same time, the level of peatiness in some heavily-peated whiskies has increased dramatically as distillers vie to produce ever more powerful “peat monsters.” In the process, they have created a new category of “super-heavy peated” whiskies.
“Peat monster” is a brand name from a particularly heavily-peated whisky produced by the specialty bottler Compass Box. Although the whisky industry has no common descriptive usage for the term, in the Scotch enthusiast community, the expression “peat monster” has increasingly been adopted to describe any very heavily-peated whisky.
Peat is an accumulation of partially decayed vegetation and other organic matter. Sphagnum moss is one of the most common components, hence the origin of the term peat moss. Peat forms when dead plant material is covered by water and prevented from decaying fully.
There are subtle variations created by the raw material that forms the peat. In eastern Scotland, peat is formed primarily from woodlands. It tends to impart a dry earthiness to whisky (Brora, Clynelish, Glen Dronach, Glen Garioch varieties). The Orkney Islands have no trees. The peat there is formed from decomposed fragrant heather and other brush. It can often add dry floral notes to whisky (Scapa). Islay peat consists of mostly decomposed moss, some brush in inland areas, and a combination of decomposed moss, heather and seaweed along coastal areas.
Sphagnum moss has phenolic compounds embedded in its cell walls. This is the source of the phenolic aromas found in peat. The wetter the area, the higher the proportion of sphagnum mosses in the peat and the greater its phenolic quantity. In addition, Islay peat is often saturated with salty sea spray. It’s believed that the distinctive medicinal flavours that this peat imparts are the result of the combination of these marine influences with the high amount of moss in the peat as it is being formed (found in Lagavulin, Laphroaig, Ardbeg, Bruichladdich whiskies).
Distillers can specify the degree of peating they want in their malt. This is measured in parts per million (ppm) phenols. A measurement of one ppm means that there is one milligram of phenol per kilogram of malt (.000016 ounces per pound of malt). Generally speaking, concentrations of less than five ppm are virtually undetectable for most drinkers.
Lightly-peated malt measures two to ten ppm. Medium-peated malt will range around 15 ppm. Heavily-peated malt will range between 25 and 55 ppm. Super-heavy-peated malts range from 55 ppm and up. As distillers compete to create ever more powerful “peat monsters,” a new category of ultra-heavy-peated malts will soon be needed. Phenol levels are measured after the malt has been dried in the kiln. Typically, between a third to a half of the phenol concentration is lost in the distillation process.
Kilning is the point in the production process when, if desired, “peat reek” can be introduced to the drying malt. The malt must have a high moisture content to absorb the peat smoke, so peat reek has to be introduced at the beginning of the drying cycle. The amount of peatiness introduced into the drying malt is a result of the amount of smoke created, the temperature of the smoke, the variety of peat used and the length of time that the malt is exposed to it.
At Laphroaig or Bowmore, for example, the malt is exposed to peat smoke for about 18 hours. By comparison, at Glengoyne, no peat smoke is used.
Wetting down the peat with water can control the amount of smoke and its temperature while it combusts. How the peat is introduced into the kiln also has a bearing on how much smoke is produced.
Bowmore distillery, for example, is one of only seven distilleries to still use traditional floor malting; a peat furnace below the kiln floor is used to provide peat reek. A combination of peat briquettes and coarsely-ground peat create heat to dry the malt and produce copious quantities of smoke. This is the traditional Islay manner in which green malt is dried before the arrival of modern fuels. At commercial maltings, on the other hand, peat smoke is piped directly into the malting drum. No peat smoke is allowed to escape through the chimney.
Both the type of peat and how it’s used in the kiln can play essential roles in creating the distinctive character of a Scotch whisky. The source of a distillery’s peat is inseparable from the final aroma and taste profile of its whisky, which is why a distillery rarely changes the source of its peat.
In Scotland, peat and whisky make a perfect match.
Joseph V. Micallef is an historian, best-selling author, keynote speaker and commentator on wine and spirits. Joe holds the Diploma in Wine and Spirits and the Professional Certificate in Spirits from the Wine and Spirits Education Trust (London). Bottoms Up is included in Troy Media’s Unlimited Access subscription plan.
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