Whisky Magazine Issue 87
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Ian Wisniewski asks what does the term ‘ppm' stand for in relation to a peated malt, and what does this signify in terms of a malt's character?
The choice of peated malts caters for every preference, from a mere whiff of smoke to a bonfire, which means that the peating level of each malt has now become a vital statistic. This level is expressed in terms of ppm (ie.
parts per million), the standard measure used in chemistry, and denotes the level of phenolic compounds which provide the archetypal smoky, peaty notes.
The peating level quoted refers to the barley (once malted and peated), and not to the new make spirit or mature malt whisky.
However, this level changes significantly during the production process, which means that knowing a malt's peating level is only a starting point.
But first let's recap on malting and peating. Malting begins with barley being steeped (soaked) in water and germinating. Any further growth is stopped by drying the malt, using heat produced by a kiln, and adding peat to the kiln creates smoke which is absorbed by the barley, essentially the husk. Adding a small amount of peat creates a lower peating level, while continuing to add peat increases the peating level correspondingly (the process taking up to about 24 hours).
A peating level around 10 ppm is considered light, and typically results in a malt whisky with a gentle waft of smoke. Around 25 ppm is a medium level, while 40-50 ppm or higher is considered heavily peated, and leads to a malt whisky with pronounced smoke.
Peating endows barley with phenolic compounds (ie. a phenolic ‘family'). This includes individual compounds...