Peat performance

Peat is a staple ingredient of many classic whiskie. Ian Wisniewski looks at the hows, and whys and wherefores of this valued element .
By Ian Wisniewski
I assumed my palate would follow the archetypal route: savouring Speyside elegance before graduating to Islay’s blockbusters. But my first trip to Islay revealed a deep commitment to everything peating can achieve. Smoky embers? Yes, please. TCP, creosote and fresh tar? Give me more, I love it.In addition to the level of peating, another consideration is the origin of the peat. As coastal and inland peat has differing characteristics, this yields a varying range of phenolic compounds – though exactly how influential this terroir is in the resulting dram depends on who you ask (particularly as the production process has a significant effect on the phenolic level). Peat cut from inland moors features a higher level of forestation and bracken, with Speyside peat for example comprising plenty of Scotch pine, roots, heather and spagnum moss (which has a great ability to retain water). The closer to the coast, the higher the level of sand, which means a looser texture, with coastal peat bogs, particularly on the west coast, also characterised by seaweed. Islay peat is a prime example, comprising pine trees, grasses, bog myrtle, heather and mosses, alongside a significant level of seaweed and sea spray influences, while sand contributes additional saltiness (being historic ‘ocean sand’). These components combine to give a lightly oily peat with iodine, medicinal, salty and even tarry notes (which can be readily identified in Islay malts). Extracting peat is obviously eco-minded, only cutting the amount required for that year, with the surface layer of turf reserved and placed over a previously cut trench, ensuring regeneration.The peat cutting season, typically April to September, reflects entirely practical considerations as peat bogs must ‘dry’ to the point when they can be walked on (or take tractors, which have been known to disappear in peat bogs). Having worked a short shift on Islay, I know I would never be hired in that capacity. It’s skilled and exacting work. The hours are awful too, a 4 to 6am start, finishing around 9 or 10 pm, as favourable weather means cutting as much as possible. Hand-cut peat is typically extracted from a trench in two stages, using a peat cutter (or peat spade) to cut a piece around 60cm long and 15cm wide. After cutting an initial surface layer, another cut is taken directly below, with each piece laid on adjacent turf to begin drying. Mechanised cutting entails pulling a machine behind a tractor, fitted with either a ‘circular’ or ‘chain saw.’ This cuts a line several centimetres wide, which can be adjusted to various depths, cutting between 0.5 and two meters (so it can be a shallower extraction than hand cutting).

Different machines have individual methods of extruding peat, which can be compressed in a chamber, prior to evenly spaced bricks of peat around 10cm square being deposited in the machine’s wake. Ready to dry where they fall, the pieces are collected a month or so later. Alternatively, peat can be continually squeezed out (like toothpaste) for the full length of the trench being worked. With a diameter of around 15cm, a skin forms on the surface within three or four hours as the peat begins to dry, preventing absorption of any rainfall. Continual shrinking, as the peat dries over the next couple of weeks, also breaks it up into manageable lengths, around 10 to 40cm long, with a diameter of five to 10cm.

Hand-cut peat typically takes longer to dry, while also requiring an additional step. It takes about two weeks for a skin to form, enabling the peat to be handled and carefully stacked with several other pieces to form either a small tower or wigwam. The wet side (the one that lay on the turf) is placed outward to ensure even drying over the next four weeks or so. Judging the moisture level is down to the experience of the peat cutter, though it’s obviously not an exact science. Consequently, peat arrives at the distillery with moisture levels that can vary from 10 to 45%, and balancing this range is part of the skill of peating. The aim of adding peat to a fire, which may even be started using redundant pieces of whisky casks, is to create a consistent level of smoke, not flames. As phenols are flammable, they can be destroyed by a flame breaking through onto the surface of the peat. Controlling the fire and peat reek entails various parameters. The more fibrous top layer of peat provides more smoke, but is more reluctant to burn than darker, underlying layers which produce more heat. Very dry peat gives plenty of heat but not enough smoke, and so not much of that distinctive flavour. Adding smaller blocks of drier peat and crumbly debris – known as ‘caff’ or ‘peat fines’ – can help impede air flow and so produce more smoke. This type of peat can also be hosed (being very dry it holds water well) and used in its rehydrated form to help cool the fire down (being careful of course not to extinguish it) and promote smoke.To maximise the influence of the smoke, which at a traditional floor malting ascends through a wire mesh floor on which the malt is spread out, mechanical turners and fans are used to help draw the smoke through more evenly. Historically malt was turned manually on the wire floor by distillery employees. As one of the distillery’s least popular jobs, it was at usually rewarded by a dram. Peating times vary from around 16 to 24 hours. This reflects the moisture level of the malt, typically 40 to 50% at the beginning of the process, with moisture promoting the absorption of smoke, essentially by the husk. As the surface of the malt begins to dry, it becomes harder to absorb smoke, until reaching the break point when the surface moisture has been driven off. Once peating is concluded, the malt (essentially the interior of the grains) needs further drying to a moisture level of around 4.5 to 5%. This entails kilning, with the kiln fired by various types of fuel, such as coke, or by using hot air, with kilning taking around 25 to 40 hours.Malt is subsequently rested in sealed bins for several weeks, which is an important procedure. As the heat of kilning pushes remaining moisture to the edges of the grain, the resting period allows this moisture to gradually extend back, and be evenly distributed throughout the grains. This ensures that milling is more even, promoting fermentability and consistency. Peating levels are measured as phenolic parts per million, with a lightly peated malt around one to 10 ppm, a medium level around 10 to 30 ppm, and 30 to 50 ppm for a heavily peated malt. Commercial maltsters, which can do the job at a far more competitive price than in-house floor maltings, originated in the 19th century, but really took off in the late 1950s to early 1960s. That’s when many distilleries increased their production capacity, but without extending malting floors. This meant maltings could not keep up with new production levels and numerous distilleries closed their malting floors. The minority retaining them include distinctive drams Bowmore, The Balvenie, Highland Park, Laphroaig and Springbank. Whoever peats the malt a similar degree of accuracy applies, with peating levels generally between three to five ppm either way of a distiller’s specifications, a range which is not significant enough to cause any concern over consistency of the new make spirit (distillers inevitably prefer the peating level slightly over rather than under). Specific peating levels can also be attained by combining peated with unpeated (or lightly peated) malt, a practise known as blending.The peating level within the malt decreases during the production process. Although this varies among distilleries, a typical reduction of 10 to 40% could apply to the new make spirit. The largest degree of loss is typically attributed to distillation, with feints, pot ale and spent lees carrying a significant level of phenols.During maturation the peating level can also affect the influence of the cask. This is usually said to account for up to 60 or 70% of a malt’s resulting flavour, though it’s more like 40 or 50% with heavily peated malts, as phenols mask the oak influence.The type of cask is another consideration. Bourbon barrels promote phenols and distillery character more readily than the richer flavour profile and sweetness of a sherry barrel, where phenols are either masked or more integrated, depending on your perspective. Peating levels do not seem to be affected during the first 20 years or so of maturation. The level can actually rise during this period, due to similar compounds, polyphenols, released by the barrel’s toasted / charred layer. While the visible longevity of phenols varies among malts, one theory is phenols begin fading after 20 years. Another opinion is that the phenol level remains constant, and as other flavours derived from the oak become more pronounced, phenols are masked. My current opinion is that I need to do a lot more tasting, then I’ll see how I feel …