PHENOLS: PARTS PER MILLION PPM

LEARNING ABOUT PEAT AND PHENOLS

Peat, also known as turf, is an accumulation of partially decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, moors, or muskegs. Peatlands, particularly bogs, are the primary source of peat, although less-common wetlands including fens, pocosins, and peat swamp forests also deposit peat. Organic matter accumulates over thousands of years to create peat deposits. Under pressure, water is forced out of peat, which is soft and easily compressed, and once dry can be used as fuel. In many countries, including Ireland and Scotland, peat has traditionally been used for cooking and domestic heating, and peat is stacked to dry in rural areas. It is harvested on an industrial scale. But it is the use of peat in the Scottish whisky industry that helps to produce a drink that has a unique flavour within the world of spirits and why different distilleries have different characteristics in their whiskies.

The peat is cut by hand using specialised tools and the resulting 'sod' is then left to dry in the open air for approximately two-three weeks. After this time, the peat is collected and then taken to the distillery. Most of the time the peat used is local to the distillery or cut from property owned by the distillery. Peat is so tightly compacted and dense that it burns for a long time and with consistent heat and acrid smoke. This is also why it is still used as a domestic fuel in some areas of Scotland, especially the islands.

Some Scotch whisky distilleries, such as those on Islay, use peat fires to dry malted barley. The drying process takes about 30 hours. This gives the whiskies a distinctive smoky flavour, called "peatiness". Peat smoke produces contains chemicals called phenols which  are absorbed by the malted barley during the drying process in a kiln. The level of phenols are controlled by the length of time that the barley is exposed to the smoke, the amount of smoke produced and the type of peat used. The smoke that has been absorbed is then carried through the entire whisky making process and right into your glass.                                                                                   

Scotch Ales can also use peat roasted malt, imparting a similar smoked flavour.

Peat can be a very divisive flavour component in the world of whisky. It is most commonly found in the single malt scotch category, although it is also present in whisky from Japan, India, Ireland, and even the Pacific Northwest. As malted barley is heated to dry it out and stop the germination process, peat is burned to infuse the grain with smoke and flavour it. As stated, the peatiness of the whisky depends on how long it has been exposed to the smoke, and measured in PPM (phenol parts per million). A measurement of one ppm means that there is one milligram of phenol per kilogram of malt. The higher the PPM, the smokier the whisky. Generally speaking, concentrations of less than five ppm are virtually undetectable for most drinkers.

There is a wide range of smoky whisky to enjoy, from light and crisp to medicinal and heavy to one of the highest PPMs distilled in recent history. If you think you don’t like smoky whisky, perhaps you just haven’t tried the right one yet. A peaty dram is best enjoyed in the winter, as the cold temperatures, limited sunlight and dreary skies lend themselves to these flavours, especially when warming up by an equally smoky fire.

These days, Malting Houses deliver specifically ordered malting to a distillery, meeting the barley and malting specifications of the distiller. At a malting’s laboratory, samples of malt are analysed for phenols, moisture, nitrogen content, and predicted spirit yield. Having malted barley peated to a higher ppm can contribute to a peatier-tasting whisky, but the ppm of the raw material is not a measurement of peat or smoke flavour in the bottle. Using the malt’s phenol ppm to predict final flavour is neither practical nor wise. The ppm of the malt remains independent of the processes involved in making whisky; the milling, mashing, fermentation, distillation cuts and maturation, each of which can affect the degree of smoke and peat flavours that reach the bottle. Leaving peat monsters like Ardbeg Supernova (100 ppm), and Bruichladdich’s Octomore 6.3 (258 ppm) / 8.3 (309 ppm) aside, recent labels on whiskies from Ailsa Bay and AnCnoc show the ppm measured in the final liquid.

Here are some examples of PPM values of some well known distilleries, as stated by WhiskyFor Everyone and others:

    Bunnahabhain (1–2)

    Bruichladdich (3–4)

    Springbank (7–8)

    Benromach (8)

    Hakushu 12 YO, Japan (8)

    Ardmore (10–15)

    Tomatin Cù Bòcan(15)

    Highland Park (20)

    Bowmore (20–25)

    Talisker (25–30)

    Caol Ila (30–35)

    Paul John Peated Cask Strength, India (30-35)

    Jura Prophecy (35)

    Ledaig (35)

    Lagavulin (35–40)

    Port Charlotte (40)

    Laphroaig (40–43)

    Ardbeg (55-65)

    Longrow (55)

    Benromach Peat Smoke (67)