Composition of Peats Used in the Preparation of Malt for Scotch Whisky Production—Influence of Geographical Source and Extraction Depth

Peat is burned during malt kilning to provide flavor compounds in Scotch malt whisky. The aim of this work was to establish whether peats from different locations in Scotland are chemically distinct and could impart different flavors. Peat samples from four locations (Islay, Orkney, St. Fergus, and Tomintoul) were analyzed using Curie point pyrolysis in combination with gas chromatography-mass spectrometry (Py-GC-MS). Peat pyrolysates from Islay and St. Fergus were rich in lignin derivatives, while those from Orkney and Tomintoul had higher levels of carbohydrate derivatives. Also, Islay and Orkney peat pyrolysates were rich in nitrogen-containing compounds and aromatic hydrocarbons, respectively. The depth of peat extraction was found to have an additional effect on peat composition as the levels of carbohydrate derivatives reduced with increasing depth. Where peat is used in whisky production, the observed differences in peat composition could potentially impact flavor, an important consideration if the peat used for malt production is changed by either choice or necessity.