Sensory and Chemical Analysis of ‘Shackleton’s’ Mackinlay Scotch Whisky from the Journal of the Institute of Brewing.
The closest to invincible any man ever got is the tag line commonly attached to Tom Crean who was Shackleton’s second officer on the Endurance. Many people I’m sure have come across numerous short articles that mention the discovery of some of Shackleton’s whisky in Antarctica or the replica that this chemical analysis inspired, but few probably have come across the original research paper on the analysis.
The paper is particularly cool and not too hard to follow. After the last two posts about Hastie’s 1920’s inquiries into pot distillation in Scotland, it might be interesting to take a look the same era but under modern analysis.
*Their analysis looks at process related congeners (operation of the pot still), fermentation related congeners (what went into the making the beer), and a look for markers that could indicate under what circumstances the whisky was aged.
“While Scotch malt whisky at the end of the 19th century was generally regarded as heavily peated and harsh in character, Charles Mackinlay & Co. Distillers were producing a malt whisky with an altogether more subtle character at their Glen Mhor distillery near Iverness. The sensory and chemical analysis of this unique whisky artefact significantly changes our understanding of the quality and character of Scotch malt whisky produced by our distilling forefathers.”
I suspect the fact that the Mackinlay whisky turns out to be really modern is what made it possible to make a replica from stocks produced in the modern era.
*They passed a sample of the whisky through a tiny filter for microbiological analysis. I guess that would tell them if any bacteria was able to grow in the bottle and impact aroma.
*They figure out the freezing point of the whisky which I suspect can explain what state, solid or liquid, the whisky has been in for the last 100 years.
*They measure alcohol strength, colour, transmittance (?), pH, and acidity (total acidity?)
*The samples get radiocarbon analysis to help rule out fraud.
*Multiple types of chromatography as well as mass spectroscopy were used to analyze all major volatile congeners.
*15 members of the Scotch Whisky Research Institutes expert tasting panel performed organoleptic descriptive analysis.
*The low freezing point and the placement below the flour of the hut may have buffered the whisky against large temperature fluctuations and prevented damage to the glass bottles.
*No evidence of microbial contamination.
*Alcoholic strength was 47.19 “and given the retention of the cork closure integrity and the apparent annealing of the cork to the glass, this may represent the actual bottling strength.” No strength was printed on the label which was not required until 1907. pH 4.3 and “no apparent loss of teh 700 mL fill volume of liquid, this initial spirit analysis data suggested the the whisky had no deteriorated during its storage in ice.”
“The flavour profiles for the three samples are shown in Fig. 4. All three samples were similar, exhibiting a balance of peaty, mature woody, sweet, dried fruit and spicy aromas. The peat levels did not dominate, while the mature flavours were consistent with maturation in sherry or wine casks. Low levels of both fresh fruit and green/grassy characteristics, and immature aromas such as feinty and sulphury were present. With no off-notes, the whisky did not exhibit any aromas not found in modern whisky.”
*Congener analysis created “fingerprint” for the whisky that didn’t different with what is currently expected from modern whiskys.
*summed concentration of amyl alcohols was at the low end of what is expected from Scotch malt whisky.
*furfural was in the middle of the expected range which indicates it was malt whisky and not blended down with grain whisky which would have a lower furfural concentration.
“The major volatile congener data suggested that the ‘Mackinlay’ was a malt whisky, rather than one blended with grain whisky.”
“At low temperatures, the long chain ethyl esters in malt whisky may precipitate and form a haze that clouds the liquid. To prevent haze formation in bottled whisky products chill filtration was introduced during the 1960’s, so it was surprising that haze obscuration was not foundin the Mackinlay whisky after its many years at low temperature. However, the choice of a high bottling strength (47.19% abv) together with low concentrations of the ethyl esters of lauric, palmitic and palmitoleic acids […], put the whisky at only a very slight risk of mild precipitation.”
*They were able to do analysis on phenols which can determine peating levels and even the likely origin of the peat. The amounts put the scotch in range of “lightly-peated” whisky currently produced supporting the sensory findings.
“The burning of peat imparts distinct flavours to malted barely during kilning, and these are transferred to the new make malt spirit on distillation. To identify the source of the peat used in the production of the Mackinlay whisky, the concentration of peat-derived phenols were compared, using principal components analysis (Fig. 5), with samples both of new make spirit and of matured Scotch malt whisky whose peat origin is known, as the impact of maturation on peat derived congeners is not fully understood. Figure 5 shows that the Mackinlay whisky is very similar to whisky currently produced using Orkney peat, confirming the historical records that peat was sourced from the Isle of Eday.”
*They are able to tackle how it was barreled just like the peat.
*Lactone ratios help support the evidence that the whisky was aged in American oak and not European.
*Concentrations of Tyrosol, “a constituent of non-distilled beverages such as sherry or wine was also identified by HPLC” […] “for a selection of ‘first-fill’ sherry cask matured Scotch malt whiskies”. So I guess they used first fill sherry casks.
*Concentrations of potassium were also in line with “first fill sherry casks rather than a re-filled sherry cask or bourbon cask, which were not in common use until the 1930’s.”
“This analysis, that relates a range of compounds to the maturation period, the cask type and the previous use of the cask, indicates that the Mackinlay new make spirit was matured in a first-fill American oak sherry or wine cask for a period of greater than five years. The sensory analysis supports this hypothesis with the whisky exhibiting the woody, sweet, dried fruit and spicy aromas typically associated with sherry cask maturation.”
*They found maturation congener 5-hydroxymethyl furfural (5-HMF) with is associated with sherry casks for wines such as Amontillado and Oloroso.
“It should be noted however that 5-HMF, as well as being a component of heat-treated or toasted casks, is also a component of burnt sugar and/or caramel. We have no reason to believe the amber tint of the whisky was not wholly cask-derived, but one cannot rule out addition of a burnt-sugar or caramel-type tint product to colour the whisky at bottling as these were available at the time.”
So there was no sugar.
“The presence of short chain acids characteristic of feints (butanoic, 2-methyl and 3-methylbutanoic acids), suggest that the cut point from the spirit to feints during distillation was made at lower alcoholic strength than that commonly used in current pot still spirit production. This later cut to feints increased the intensity of cereal popcorn aroma” […] ” and that of earthy/mouldly leaf aromas”
*Now they get into ethyl carbamate which is something new to me. This congener is considered carcinogenic and I’ve come across papers recently that describe it as a regulated compound and show efforts to reduce it in spirits. The levels they found were consistent with low levels currently found in modern Scotch production.
*They mention older barely varieties in use at the time what had more ethyl carbamate precursors. I guess varieties were changed to reduce this congener.
“Given that the level of the ethyl carbamate precursor, epiheterodendrin, may have been relatively high in the older barley varieties used during the late 1900s [typo?], the low concentration of ethyl carbamate reported here suggests that the distillation in the copper wash still was carefully controlled to prevent frothing of the wash and fouling of the copper spirit still.”
I don’t really know how to interpret this quote. So they are careful and avoid puking of non-volatiles during the first distillation and that is really enough to cut down on ethyl carbamate?
*They mention another compound, NDMA which is produced during kilning, that is surprisingly low, given that efforts were not made to reduce it until the 1980’s.
“The levels of process-related compounds, such as ethyl carbamate and NDMA and the metal and cation/anion content, are consistent with those currently found in malt whisky, and give us an insight into a controlled production process. The results presented here significantly change our perception of the quality and character of Scotch malt whisky produced over 100 years ago.”
Simply amazing. It is astounding what modern analysis is capable of telling us about such a spirit sample. A brilliant work.
One bibliography entry jumps out at me as being really interesting but I cannot seem to find it:
3. Clutton, D. and Simpson, A., The shelf life of spirits. In: Elaboration et Connaissance des Spiritueux: Recherche de la Qualite Traditoin et Innovation R. Cantagrel, ed. Lavoisier-Tec & Doc: Paris, 1992, pp. 548-556.