Peat source and its impact on the flavour of Scotch whisky

Peat is used as a source of flavour compounds in Scotch malt whisky production when it is burned during malt kilning. The aim of this project was to establish whether peats from different locations in Scotland are chemically distinct and could consequently impm1 variations in flavour to m:t1t whisky. Peat s:lI11ples from four geographical locations (Islay, Orkney, St fergus and Tomintoul) were distinguished by Fourier Transform Infrared (FT-IR) spectroscopy. Analysing peat samples using Curie point pyrolysis in cOll1bination with Gas Chromatography-r-.lass Spectrometry (Py-GC-MS) showed that peats 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 peats were rich in nitrogen-containing hcterocycles and :Iromatic hydrocarbons respectively. A labol':ltory-scale pealillg)rocess was developed :lI1d malt was prepared using peat from the fClllr locations. 'j'his .11alt was mashed and ll.'rmented and the wash distilled on a laboratory-scale. Analysis by GC-MS showed that some peatderived compounds such as lignin-derived syringols were not transferred to the spirit. Nevertheless, principal components analysis of the GC-MS data revealed that the spirits grouped into a similar pattern as that derived from the peat analyses. Assessment of the spirits by sensory panel revealed significant flavour differences; in particul:lr spirits prepared with Islay peats were distingdished by burnt an.! smoky aromas. These lindings indicate that if distillers change the source or their peat, either through choice or by necessity, they must take into account the possible inth:ence that this could ha\\(~ on the flavour character of their product.