Sensory and Chemical Analysis of Shackleton’s Mackinlay Scotch Whisky
James Pryde, John Conner, Frances Jack, Mark Lancaster, Lizzie Meek, Craig Owen, Richard Paterson, Gordon Steele, Fiona Strang and Jacqui Woods, J. Inst. Brew. 117(2), 156–165, 2011
The discovery of crates full of Mackinlay whiskies at Sir Ernest Shackleton’s hut in Antarctica generated a high media impact. Whyte and Mackay, the current owner of the Mackinlay brand, after negotiations with the Antarctic Heritage Trust, received the authorization to extract some whisky samples from 3 bottles of whisky. The article describes the chemical and sensory analysis of the whisky contained in those bottles in order to identify the process used in the whisky making process used at Glen Mhor distillery in the late 1890s-early 1900s. The Rare Old Highland Malt Whisky should be a Glen Mhor single malt whisky, according to archives.
|A replica of the original Shackelton's Mackinlay whisky from the 1907 expedition produced by Whyte & Mackay in 2011 by the Master Blender Richard Patterson.|
Pryde et al., tried to answer several questions:
By recording the temperature profile in 2010 and determining the freezing point (temperature at which the frozen whisky would turn liquid) which was measured as -34°C , knowing that the whisky was kept under ice , in absence of any damage to the glass bottles and external signs of leakage, the probably of changes to the flavour profile by thawing-freezing cycles is assumed as unlikely. Futhermore, no haze could be observed in the liquid, thanks to the relatively high strength of the liquid (47.2%). Further chemical analysis (anion/cation and heavy metals) did not suggest any major contamination of the spirit by the containers (glass or cork). Thus, the low temperature should have not impacted negatively on the quality of the spirit.
Chemical analysis of the congeners, in particular amyl alcohols and furfural were indicative of single malt whiskies distilled by pot stills. Analysis of the phenolic (i.e., “peaty”) compounds classified this whisky a “lightly” peated whisky based on the concentration of the total phenolic compounds. Based on the composition and distribution of those phenolic compounds using a principal component analysis (see my article about the influence of the origin of the peat for further details) it could be determined that the peat used for kilning probably came from the Orkney, confirm to historical archives.
Determination of the 14C was compatible with a whisky distilled in the period of Shackelton’s expedition. Concerning the age of the content, analysis of the lignin breakdown products (i.e., extract coming from the wood of the cask) syringyl and guaiacyl was compared with data from current matured Scotch whiskies indicated maturation in oak casks for a period of at least 5 years, but more likely closer to 10 years.
In addition to standard chemical analysis, the samples were subject to sensory analysis by a panel of 15 sensory experts as well as by gas chromatography –olfactometry (i.e., compounds separated one by one and nosed) by 2 observers who assessed the intensity and description of each extracts. By combining all these analytic methods and human nose, the whisky was assessed as “very complex”.
By quantification of anions, cations and heavy metals, contamination of the spirit by the container excluded major contaminations. Traces of a furfural derivative (5-HMF) associated with burnt sugar suggested either the use of toasted or charred cask and or the use of small amounts of caramel. Presence of some allyl alcohol indicates that the wash has been infected with lactic acid bacteria before distillation. This could have been introduced by the malted barley, the use of malted barley or from the microflora present in the distillery. The presence of short fatty acids indicated that the cut point for the spirit was made at a lower alcohol strength than used nowadays (i.e., more feints).
How the whisky was produced
As mentioned above, peat from Orkney was probably used for peating the malt and a lower cutting point was used for the spirit, as well as the use of brewer’s yeast. Presence of the ethyl carbamate precursors was high in the old barley species but low in the whisky suggesting that the distillation was carefully controlled. Low concentration of NDMA also suggests the inclusion of sulphur containing coal to augment the drying process (and to allow better storage of the malt). The anion/cation and heavy metals analysis was compatible with good water and absence of contamination in the distillation process.
Type of casks
The sensory analysis was consistent with maturation in wine (sherry) casks and analysis of congeners, in particular the ratio of the cis versus trans lactone isomers were indicative of American oak. Furthermore, tyrosol, a component present in sherry or wine were also identified, as well as high concentrations of glucose and fructose, suggestive of first fill casks. Altogether, these results indicate the use of first fill sherry casks made with American oak.
The chemical and sensory analysis of the Shackleton’s Mackinlay Highland Malt indicated that the whisky was not altered by its 100 years long storage at low temperatures and that the whisky contained in the bottles analysed is certainly a single malt from the lost distillery of Glen Mhor matured for 5 to 10 years in first fill American oak sherry casks. The whisky produced was of high quality and lightly peated.
This work is give us an impression of the quality of the distillation process in the early 20th century and surprisingly (at least to me), was the use of sherry casks made with American oak.
I could unfortunately not taste the original Shackleton, but the replica assembled by Richard Patterson and the White & Mackay team was surprisingly similar to an old blend from Berry Bros & Rudd from the same period I recently tasted. If these whiskies were representative of the production at this time, then the whiskies were not always as coarse and peaty as some authors suggest it.
Dr P. Brossard ©12Nov2011