Production

Meet peat

In the latest in his series on whisky terms,Dominic Roskrow addresses part one of a two part look at the letter P, and makes sense of peat,phenols and PPMs
By Dominic Roskrow
Whisky is defined as a spirit made with grain, yeast and water only, and a single malt whisky as one made at one distillery using only malted barley,water and yeast.With the exception of allegedly flavourless caramel colouring, nothing else may be added to malt whisky.This, though, isn’t the whole story. One of the key components to some of the world’s greatest whiskies is, of course,peat,and while it isn’t actually added to the whisky-making process, its presence can fundamentally help define the taste of a malt.Peat’s role in the development of the flavours of whisky is twofold; through its presence in natural water and through its use in the drying of barley once it has been soaked in water and ‘tricked’ into growing.Contrary to what many people think, the effect on taste of peat in water is very minimal. It is true that much of Scotland and Ireland’s natural water sources pass through peat bogs and often its presence is reflected in the deep brown colour of the water.But the fermentation and distillation process distance the final spirit from the peat in the original water, and although traces of peat can sometimes be picked up in whisky where no peat-dried barley has been used, it is relatively small.Peat imparts phenols to the malt and these are measured in parts per million (PPM).The effect of peat in the original water has been measured in the final mix as as little as 1PPM.Peat smoke from the drying process is another matter. It will impart a very high level of phenols and must be controlled carefully.A strongly peated malt from Islay, for instance, will have a PPM level of about 45 or 50PPM and the grain used will include a good proportion of unpeated braley.Peat is the mass of vegetation and natural debris that has rotted and carbonised over decades and centuries and which, through heat, water and pressure, has created a decaying and suppressed substance that will eventually become coal.As a resource peat has a huge environmental significance as it produces carbon dioxide.But it makes a great natural fuel and would have been used in the drying of barley for use in most Scottish whisky. Its importance diminished in the wake of the industrial revolution and the growth of the train network, which permitted the transport of fuels such as oil and coal.Geography and regional economics explains its continued importance in the islands.The depth of the peat dictates how concentrated it is, and for whisky making it is often divided in to three types: fogg, which is the lightest top layer and which burns faster and with the most smoke; yarphie, which burns slower and is the middle layer; and moss, which is like chocolate mud pudding when wet and like coal when dried, and burns longest.Peat is rarely used in Ireland, though the country is rich in it.That’s because the commercial export of Irish whiskey started early in Ireland and production of it moved from the country to the cities. It rapidly became economically unviable and its usage died out very early on.POTALE After the first distillation in the wash still a residue remains and this is known as pot ale.It is also occasionally known as burnt ale or spent wash,and it is high in proteins.It can be treated and turned in to a syrup or solid to be used principally for animal feed,though it has been used as a fertiliser POTSTILL The copper kettle-like vessel in to which distiller’s beer or wash is put and heated to create distillation.Normally but not always distillation takes place twice – first in a wash still,and then in s a spirits still.Itconsists of three parts:the pot,the neck and lyne arm, and the condenser PURE The term ‘pure’has been widely discredited in recent years because it had no clear definition.It has been used on single malts,on vatted or blended malts and on blends and is now effectively banned as a descriptor