Hastie, circa 1925, and the new era of pot distillation

The Application of Chemistry to Pot Still Distillation by S.H. Hastie, O.B.E., B.Sc.

This is another newly digitized paper accessed from the Wiley Online Library.

In this paper from 1925 Hastie kicks off the systematic exploration of aroma/congener-centric pot still operation.  This work is unique because Hastie is particularly smart and presents the paper in front of very illustrious people yet somehow does not make it into bibliographies that follow.  Maynard Amerine did not reference Hastie in the 1941 Commercial Production of Brandies, Peter Valaer never referenced Hastie in any of the IRS papers, and Roseworthy Agricultural College never referenced Hastie in the decades to follow where they conducted similar work even though they were aware of Joseph Nettleton’s works.

The paper is not specifically useful to a new distiller but it does set the scene in the history of modern distillation and explains what was known and unkown at the time as well as implies how much control and consistency distillers had over their process.

What is particularly interesting to me is how advanced brewing was relative to distillation.  So much science was already applied to malting and brewing but science hadn’t even explained the effect on character of running the pot still fast or slow.  Art had produced many good rules of thumb but science had not explained them. Joseph Nettleton’s works predates Hastie’s and because of these giant gaps in knowledge that Hastie identifies, Nettleton’s tomes come across as basically just a treatise on brewing for distillers (not that that isn’t important!).  Whiskys back then were probably damn good as proven by the recently analyzed Mackinlay that once belonged to Ernest Shackleton, but they still had one foot in the dark.

From reading the commentary sections of Hastie’s other / papers, I suspect that overly strict excise rules may have strangled attempts to elaborate the ins/outs and what-ifs of pot still operation.

Hastie is very tactful and pragmatic when he lays out his plan for advancing distillation.  He carefully fragments the process so analysis can be conducted at every step of the process instead of just with the end result.  That way if something goes wrong it is actually possible to pin point the cause and correct it which he acknowledges is difficult is these stodgy, conservative operations.  I suspect a lot of the new American distilleries running on no sleep and shoe string budgets do not conduct much analysis or are even aware of what is possible. If that is the case, these new distillers will greatly benefit from brushing up on Hastie and Nettleton.  Analysis currently is so advanced and can be cross referenced against so much great data that the team led by the Scotch Whisky Research Institute was even able to identify the peat source of a hundred year old whisky sample.

Few people read the original papers so let me extract and discuss some choice quotes.  The chemistry at the end of this paper gets pretty dense and I suspect Hastie errors a bit so I will try to compare Hastie’s work to that of Roseworthy Agricultural College and even the most current explanations as best I can.

We should probably first begin at the end:

“If I should have succeeded in arousing interest in this complicated problem sufficiently to attract any additional workers to this field of investigation, then I will be more than satisfied.”

“Subsequent to the war, however, science has forced itself upon the attention of the conservative distiller, and efforts are now being made to apply laboratory control to pot still distillation.” It is strange here how the war is credited as a catalyst for advancement. More than a decade later, war is credited again as steering W.O. Graham into exploring distillation for his thesis.

“Perhaps at this time of day it is not necessary to point out that a scientist must not be expected to enter a distillery and after a few months effect fundamental changes, for nothing short of a magic wand will operate in this way, and fundamental results arrived at thus rapidly, are in the light of experience in other directions, very likely to prove misleading.” This is really interesting because so much great work was conducted at Roseworthy on pot still operation and many of its graduates entered the industry but the Australian distilling industry was barely changed.  Patience and tact might be of the utmost importance in the distilling industry.

“In a word, if we are to advance at all, the pioneer work must be carried out by technical men with scientific training in biology, chemistry and physics, with, and this is of the first importance, practical connection with and knowledge of the daily operations of the distillery.” And here we reach the limitations of any advice I can give anyone. I’ve learned a ton about distillation but I certainly have not operated a distillery and have no clue how my ideas can scale to the day to day of hundreds of gallons of this and that.  I’ve heard so many similar anecdotes from the wine industry. Lots of kids graduate from oenology school but they can’t take apart, repair and fix the pumps that move the wine around.

“This state of affairs resulted from a very superficial knowledge of a very complex and conservative rule-of-thumb series of processes, of the precise workings of which the general information was, and still is, very meagre.” Hastie starts to make his case for science and analysis by examining what happens when a certain amount of grain produces a less than expected yield.  Previously it was pass the buck and the blame game and distillery operations were not well fragmented or systematized to identify where the problem started.

“Considered as a rule-of-thumb process without guarantees of yield, the process is very simple, but considered as a problem in the production of full yields of a definitely uniform product the subject bristles with difficulties of the most complex kind.” Cooking is slowly being elaborated in a similar way these days with the advent of temperature controlled cooking and baking scale style recipes popularized by Modernist Cuisine. I’ve talked about this in the past with classic cocktails where recipes go from dynamic towards static.

“Quality and character are the prime essentials of the business, and all that I may say as to the value of control is to be taken subject to the proviso that this control is of economic value, and where it has affected existing character it has improved it, and has certainly not proved detrimental.” This relates to my notion of involvement.  I think people thought character was the product of a lot of chaos and mystery. Things were made with a low degree of involvement so the magic could happen by itself.  Being too conscientious risked stripping the magic away. If something could be more efficient, bureaucratics would push it that way to a point which compromised character. But this was a lot of short sighted thinking.  Control and systematic study could help eliminate flaws, regrets, missed opportunities and ordinary aroma thus cultivating extraordinary, singular character, terroir.

Hastie goes on to subdivide the production of distilling material into malting, mashing, and fermentation where maximum theoretical yields are calculated for each segment to isolate problems. “We thus ascend from art to science.”

Hastie starts to explain the analysis of the fragmented processes which I think was well adopted by brewers but not yet by distillers. Examine barley and determine starch percentage and germinative capacity. Assess nitrogen percentage. Kiln barley to assess moisture content using a moisture standard of 3 per cent for extract obtained. Grist is evaluated because malt is subject to change with storage. During fermentation gravity is examined to be compared against gravities for ferementation completion.

Control of the yeast supplies is where things get really interesting to me.

“Hitherto the scientific care of yeast both as to storage and control in pot still distillery work simply has not existed.”

Previously I had no idea how distillers were getting their yeast. I thought they must have proprietary supplies not related to beer brewing.  I suspect American whisky producers had all the same practices though I’ve never read anything to confirm it.

“As soon as the brewer has finished skimming and pressing, the yeast surplus is dumped into the general sump which is the distiller’s source of supply, from there it is forwarded (in casks or pressed in sacks) by rail and to the Western Isles by cargo steamer. It is frequently on deck in the heat of the sun, uncovered, it is collected at leisure and stored in the distillery yard regardless of temperature or anything else, and is finally drained off in buckets through a cock in the cask, the mouth of which is filthy as a rule with dried yeast, etc., from previous buckets. It is then tipped into the wash back to ferment the wort and is by this time a mixture of doubtful cleanliness, of very uncertain vitality, and certainly always a seething mass of organisms of every description. Truly a picture black enough to make Pasteur, the scientific father of our allied industries turn in his grave.” Wow, very surprising.

“There is no doubt that the yeast used is frequently blamed for defective fermentation, when the wort is the real determining factor, and so long as worts are prepared, may I say scientifically, blindfold, the distiller cannot definitely say whether the yeast or the wort is the cause of unsatisfactory results, but by controlling each of these factors he may strengthen his position enormously when complaints have to be made to the provider of his yeast.” I think that these days the yeast companies are so good that we almost do not have yeast problems.

“In the application of the system, graphs are plotted of efficiency coefficients which are kept throughout the season, and afford immediate comparisons of various distillery productions in all departments of process on a basis strictly comparable, and independent of the nature or quality of the barley employed. Distillers are prone to compare the produce of different distilleries, although the materials may vary so much that such a comparison is unfair to the operative distiller and quite worthless.”

“…control is the desirable jumping off point and must precede research. Control must come first and be complete and research must follow as the outcome of control.” I wonder how Hastie would feel about new distilleries. Do they have enough control and involvement to justify new explorations and attempts to be differentiated in the market place.  Can organoleptic analysis via tasting panels be counted on for control?

And now we to Hastie’s research ideas some of which are really interesting:

“The mashing process. The question of extra yield.”

“there is the question of treatment of mash and mashing water with inorganic salts. Nettleton in his book on distilling states that 20-40 grains per gallon on salts such as NaCl or CaCl2 will enhance the diastic power and increase the amount of protein matter dissolved in mashing.” Hastie goes on a little more and I am definitely in territory I know very little about. I’ve learned quite a bit about operating a still, and of fruit based wine making but I know comparatively little about brewing.  I was under the impression that NaCl seriously inhibited yeasts but it would be interesting to see how these amounts translate to g/L and therefore how much of an interesting water source could be used such as ocean water to also add organic material as well.

“From further work carried out on this question and not recorded here, as being still in progress, the opinion has been formed that the hydrogen ion concentration of the mash water and mash materials was the real factor operating in these experiments and in those of Nettleton, as adjustments of the Hydrogen ion concentrations of the water taking into account the mashing materials has a greater and more definite effect upon the yields than the addition of salts alone, and further the effect of these additions is found to be largely due to their influence upon the pH of the mash, and is, in fact, an inefficient “trial and error” method of adjusting the pH. The adjustment of the pH of pot still distillery mashes and worts is of the utmost importance to distillers and is at present the subject of investigation, but it is regretted that further details cannot be set down here meantime.” Super interesting! What I think they are arriving at here is the sour mash process.  The pH is adjusted not just for microbiological stability but also for yield, and from other papers I suspect as a catalyst for esterification in the still. I was under the impression that Scotch whisky distillers did not exactly sour mash but that might not be the case or maybe they just adjust it by different means.  What is also interesting is about the same time in Australia, Alan Hickinbotham of Roseworthy Agricultural College was revealing the significance of pH to the stability of wines.  Prior, something like 20% of wines were sent to distilleries because they were essentially spoiled but after acid additions were made to adjust pH, that number went down to 3% and still wine product increased very significantly.

“It must be remembered, however that the success of the treatment of the mash is determined not by the water composition alone, although this is of importance, but to a much greater extent by the pH of the mash as influenced by the malt used.”

Hastie acknowledges skipping fermentation in the paper because he wants to focus on the operation of the pot still.

“When a definite scientific method of control has been arrived at, then attention may be turned to the origin of the substances stamping the character on spirit, but so long as the distiller is in the dark as to the precise effect of varying the distillation process with a given fermented wash, it is premature to enquire into the origin of the character producing impurities in the wash.” Hastie starts to propose working backwards.

“That is to say, we must deal with the second and final distillation first, wherein separation and interaction of substances takes place,  before we are in a position to deal with the primary distillation where separation and interaction of substances also takes place, but where in addition new substances are actually produced not previously present in the wash.” Hastie sees the second distillation simpler than the first. A lot of magic happens in the first distillation and it is probably not fair to relegate it to a “stripping run”.

“In this way the control of the selection of the different desirable materials from the wash, and the exclusion of the undesirable, must be definitely settled, and then the origin and nature of the substances can be tackled.”

“To digress for a moment in explanation of what follows, it appears to be the case that after the Royal Commission on whisky had given its findings the tendency was to attempt to eliminate partially or wholly many of those impurities from pot still whisky which constitute its commercial asset and as the amounts and nature of these impurities are of first importance, the endeavour of the distiller is now to attempt to retain definite proportions of them in his whisky where such is already in active demand, or to attempt to incorporate the desirable and eliminate the undesirable, where the existing demand for his particular product is small.” I wonder if the popular press created a demand for lighter spirits once they had namable compounds to write about and falsely implicate in hangovers. David Wondrich could probably give us some nice background on this idea. Hastie goes on to say that whiskys with undesirable character could be stripped of it and used for blending with other whisky of more desirable character.

About congeners: “They are doubtless largely derived from the peats used in drying the malt and also found in the water which in the large majority of cases (in Highland whiskies) drains through peaty soil.” This paper pre-dates Hastie’s other paper where he spends more time on water.

“We will therefore start with the product of the first distillation that is, the low wines which in practice is normally collected and mixed with the foreshot and feints, that is, the first and last runnings from the second and final distillation of the previous period.” Here we see acknowledgement of the recycling of fractions.  The Roseworthy papers explain a lot about recycling because it was not common practice in Australia despite being integral to Cognac production. It is also super important to realize that whisky is the product of interlocking batches.

Hastie presents a chart that gives some numbers for the composition of low wines + feints + foreshots (volatile acids, esters, higher alcohols, aldehydes, furfural).

“[…] in addition to which a small proportion of other very important character giving bodies are present of which practically nothing definite is known beyond their undoubted existence, […]” He realizes due to analysis constraints he is not working with a complete picture.

“The function of the second distillation therefore is to select primarily, in the whisky or second fraction an alcoholic distillate containing the above, and to exclude from this fraction by collection in the foreshot and feints and rejection via the spent lees, the undesired balance of impurities.”

Hastie presents more great data sets. One particularly cool data set looks at the second distillation (only via laboratory still) and shows the accumulation or trailing off of every major congener class over the course of 19 fractions. We should probably compare Hastie’s data against the brilliant charts of Robert Léauté’s 1989 James Guymon Lecture.

“[…] general uncertainty of the distillation as a process of separation.” All these things are being thrown at you at different rates and you have to catch them. There are lots of moving parts.

Hastie presents another data set of 80 fractions taken at 15 minute intervals from an actual spirit run in the distillery. The previous data set was only from a laboratory setup.  Getting real world data is a remarkable feat back then because of excise restrictions on sampling. Esters do some very erratic things in his data set.  He notes that laboratory results and real world results differ.

“One of the obvious methods in practice by which a given character may be altered always presupposing a definite low wines and feints and foreshot mixture is by collecting less foreshot or more foreshot, less feints or more feints, etc.”

Hastie spends some time explaining what happens when you enlarge or contract the cuts but then notes that those options are obviously limited and other methods need to be sought out for modifying character (changing starting proofs by altering recycling, altering time under heat, altering lyne arm to effect subtle reflux rate).

“One can readily understand that any factor tending to greater or less rectifying effect of the apparatus will at once alter the character. Such factors are increasing the height or diameter of the still neck, and inclining the lyne arm; and the use of plant designed to partially condense the spirit and so return a proportion to the still will have similar effect.” The very last part here I think refers to what is sometimes called a brandy ball. It isn’t exactly a reflux column but rather just a simple way to add more reflux to a pot still. Usage was described in the Roseworthy papers but I haven’t seen one described anywhere else don’t think any producers currently use them.

“The speed at which the distillate is driven off from the still will also have its mechanical effect on the product. As an instance of the effect of one of these factors a few tests of runs of laboratory still using the types of head and lyne arm detailed are given to show clearly how one of the variable impurities of the character producing substances, namely acid, actually reaching the whisky is varied with different apparatus.” The speed has a two-fold effect. Firstly changing the time under heat, by changing the speed, varies congeners creation in the still and secondly increasing the speed challenges the natural reflux of the still head.  Explanations for these phenomenons where hard to come across but were explored in the Roseworthy projects. A pot still has more reflux options than you’d think and besides the rate of distillation, changes to the lyne arm such as angle or length can change alcohol content of distillate and thus congener distribution markedly and this was again explored in simple experiments at Roseworthy. Hastie provides drawings of different laboratory lyne arm options and shows a chart that illustrates how each option varies in volatile acids collected. I think his chart could be set up better.  The options with the least amount of reflux collect the most volatile fatty acids.  The volatility of these fatty acids, it must be remembered, is a function of both their boiling point and relative miscibility in water/ethanol so when reflux is varied, and thus alcohol content of the distillate varied, this relative miscibility becomes a big factor in explaining volatility.  My favorite better explanation of the subject comes from Amerine’s Commercial Production of Brandies.

“[…] as the impurities tending to come over in the distillate vary with the alcoholic strength of the vapour some tending to remain in the still at the higher strengths, and others tending to pass over, consequently more or less rectification will mean corresponding differences in the amounts of the different impurities actually passing into the distillate.”

“Schridrowitz (loc. cit.) pointed out that the simple distillation of low wines, etc., gave rise to changes in the amounts of the constituents in spirit with elimination of impurities via the spent lees.” Distillation on the lees was also explored at Roseworthy because it was common practice in Cognac but not Australia. It may seem counter intuitive that distillation on lees could reduce impurities such as aldehydes.

“The process of distillation of the low wines, and feints in the spirit distill is essentially a process of hydrolysis of the esters giving acids and water of oxidation of the alcohol to aldehyde, of production of esters from alcohol in presence of acid, oxidation of alcohol to acetic acid, and many other subsidiary actions no doubt.” Hastie sets out to tackle the reactions taking place in the still.  I am well acquainted with the esterification reaction but the hydrolysis reaction where esters split apart is somewhat new to me, but explained particularly well by Peter Atkins in his book on chemistry, Reactions.  Hastie seems to think the splitting apart of esters is more common than the formation of esters in the still, but I’m pretty sure he is incorrect.

“Apparently the distillation in the normal courses in practice increases the acids at the expense of the esters and decreases the esters, due to the interaction taking place between an alcohol and acid mixture in presence of esters and water. When the low wines + feints + foreshot are subjected to hydrolysis under a reflux condenser a similar effect is observed on the total acids and esters. Further when hydrolysis for one hour is followed by distillation the cumulative effect is a smaller increase in the total acids and a smaller decrease in the total esters in the fractions.” One thing to note here is that I’m pretty sure Hastie is dealing with the second distillation where there is no non-volatile acids to catalyze esterification.  So maybe esters are predominantly formed in the first distillation then unravel to a small degree during the second distillation then even reform post distillation as everything reaches an equilibrium.  Non-volatile acids absorbed from the barrel, it should be remembered, will influence this equilibrium. The refluxing Hastie mentions has the effect of pushing the solution towards equilibrium but distillation is not at equilibrium because the alcohol water concentrations are always changing as vapor leaves the distill.  The French also note that best results of double distillation are achieved if the second distillation happens quickly before the low wines can sit around and approach equilibrium.

“In these tests and in those which follow, the total amount of esters destroyed does not agree with the total amount of additional acid found, except in those cases to be given in detail below where alkali was added to the liquid before hydrolysis and distillation, the use of alkali limiting the number of possible reactions and allowing of more definite conclusions.” I don’t completely know how to interpret this. The only thing I can think of is that when ethyl acid is broken up it could become plain acetic acid or acetaldehyde. I can’t remember the names of the processes for aldehyde formation.

“This is probably a case of the reversible reaction known to occur between acids + alcohol and esters + water. The acid and alcohol heated together, yield esters up to the equilibrium point dependent upon the conditions of temperature and relative quantities of alcohol and acid present.” I think something he is missing is pH influence from other non-volatile acids. this comes into play during the first distillation where significant non-volatile acids are present and then again in the barrel where pH drops due to the accumulation of new non-volatile acids.

“[…] and although an equilibrium point should be reached theoretically after a definite amount of hydrolysis, this equilibrium point will never be actually attained in distillation as the total esters and alcohol vary in amount as distillation proceeds, and products pass to the distillate.”

Hastie goes on to explore distilling a low wines + feints + foreshots mixture in the presence of sodium hydroxide (lye) to see what happens. He determines that the formation of esters and the splitting apart happens simultaneously in the still.

“When the conditions are, as in practice, those of distillation, the hydrolysis of esters will occur, and the production of esters will also take place, but an equilibrium point will not in fact be reached, owing to the removal of varying amounts of the interacting substances to the distillate.” This lack of equilibrium is why new make spirits can change so markedly in the first few months.

One thing that definitely needs to be noted is that Hastie is only looking at the second distillation of double distillation. The first distillation is very different because of all the non-volatile material that influences pH and thus equilibrium and also possibly provides a fixative effect reducing the volatility of certain compounds.

from the discussion section worth noting:

“He did not agree with the suggestion that character might be determined by local bacterial conditions, so far as to account for differing whisky characteristics in the distilleries in a district.”


Mackinlay Scotch: The closest to invincible any whisky ever got

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.”

shackleton spider “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.

S. H. Hastie and W. D. Dick on Furfural and some other distillation gems.

A great paper, Character in Pot Still Whisky Part II, from Hastie and Dick in 1928 which provides a lot of information on furfural and some real gems on the state of distillation at the time.

The main section is sort of technical and won’t interest the non distilling connoisseur but the comment section at the end is full of wonderful gems that explain the state of the industry in 1928. I hope to find as many of these papers with comment sections as I can.

“There was one thing Mr. Hastie had remarked upon early in the paper which provoked a smile, and that was with regard to the cleaning of the stills. He himself could give a case in point in which the absence of cleaning of the stills might have a very considerable influence on the character of the whiskey produced. He was in a certain distillery for about a week some years ago and a very conscientious still-man was in charge. At the end of the period the whisky was not what was desired, and one of the proprietors told him that the whisky tasted in a manner which they had been trying to prevent for the previous five years. When the still-man was cross-examined it turned out that he had been rather too energetic in his cleaning, and had cleaned beyond the point to which he should have gone in order to maintain the characteristic flavour of the particular whisky.” The impact of copper on distillation is very complex and apparently copper can be too clean. One other paper concerning copper more specifically describes their priming of their experimental still before they studied what effect copper had on the distillate versus stainless. So far I haven’t come across any hard and fast rules of thumb. I suspect over cleaning might be a problem for new distilleries because they are often sharing one still among many products that they make such as a vodka, whisky, and a gin.

“He decides to discontinue the collection of “foreshot” and to commence collecting potable whisky when the distillate no longer turns blue and clouded when water is added in time-honoured fashion. He later decides to cease collecting potable spirit and to proceed to collect the third and final fraction by observing the alcoholic strength of the distillate, experience telling him at which particular strength to affect the change over for the particular plant with which his is concerned.” I had never heard this about a blue distillate identifying a heads cut. It makes sense because that is when corrosive fatty acids are at their highest but I wonder how this rule of thumb overlaps with approaches now based on mass-spec and empirical taste thresholds.

“It was a pity that samples could not be taken during the actual distillation, but he was afraid that the easy going ways of the South of France would not be allowed in this country.” This gets revisited later but excise rules were so strict that there were no provisions to legally collect samples for research.

“It seemed, however, that whisky was produced more by tradition than by science, and a man who had a distillery which could produce a full whisky had a valuable asset.” I suspect the audience is mostly full of brewers and their science was much further ahead of distilleries.  Success back then of a distillery seems to be mostly by chance.

“Mr. Hastie had suggested that furfural was largely produced by caramelization and he
wondered if it were possible to remove the rousers from the stills. Years ago all the
coppers at his Chiswick brewery were fitted with the rather alarming chain rousers,
which were practically impossible to to keep clean and needed constant renewal.
Contrary to all the traditions of the place at that time, he had insisted on removing
the rousers, and the coppers were much easier to clean in that they were unhampered by
the rousers, and except that the bottoms of the coppers showed a certain amount of
caramelization, the rousers were never missed. Possibly the little extra
caramelization which was obtained in this way would produce more furfural.” The “he” here is not Hastie but another commentor with brewery experience.  Rousers basically stir the pot to prevent burning. They are hard to clean and I guess this brewer thought he could do without them. 

“He seemed rather to have given the impression that distillers never cleaned their plant. He should, perhaps, not have said that the stills were never cleaned, but that it was not the custom to remove the deposit which was automatically left in the worm and in the lyne arm by the action of distillation. It was that, rather than that the distilleries were not cleaned, because the fermenting and other vessels were scrupulously clean.” So distilleries were clean, but deposits were just left inside the stills because it was known to effect flavor. No one knew the science of this back then and it still isn’t well understood.

“A curious thing was that certain countries which import whiskies in large quantities now insist upon a signed analysis by and independent analyst showing that the particular whisky imported contains a certain percentage of furfural, and if this whisky does not show, on analysis, the prescribed proportion of furfural, it is rejected.” Peter Valaer, the IRS chemist, touched upon this and furfural content implied the methods of production and whether a spirit was cut down or not. Genuine pot still whisky, which will have more furfural than something like patent still whisky, is worth more because it is typically uncompromising and gets a longer time under heat which is expensive. Stocks of pot still whiskys were often bought to be blended.

“The yeast used by distillers was mentioned by Mr. Reavenall who stated that distillers did not seem to care what sort of yeast was used. The fact was, however, that Mr. Reavenall probably knew more about distillers’ yeast than the distillers themselves, because they bought their supplies from brewers and had to take what they could get. So far as his own particular process was concerned it did not matter where the yeasts came from so long as it was good, and sound and clean. There was no question of a pot distillery requiring anything in the way of a pure culture. As a matter of fact, better results seemed to be obtained by taking a mixture of yeasts obtained from different sources rather than from one source only, although why that was so he did not know.” I’ve heard only a little of the importance of distillery yeast and have wondered what new American distilleries were using. I wonder if Bourbon producers hype the importance of their yeast strains to create almost false exclusivity or if they have actually experimented widely and truly know the differences.

“He also agreed with Mr. Reavenall as to the annoying Excise restriction. The fact was that the distillery was hardly controlled by the distilling firm. Everything must be done in accordance with the Excise regulations, and as an example of the difficulties, he mentioned that he had once desired to take samples every quarter of an hour from a still during a four hours’ operation, in order to examine the samples, but although he tried every possible way to get permission they would not allow him to take 20 cc. samples at quarter of an hour intervals throughout the run of the still.” Really fascinating is how the excise restriction shaped the spirits industry and caused them to lag behind breweries in terms of a scientific understanding of their craft. I wonder though if it ended up being a positive and preserved traditions that are more fragile that people think.

“The question of fire heating versus steam heating was of importance in connection with pot still distilling, and it had been found that the character of the whisky was frequently detrimentally affected by reverting to heating the wash still wit a steam coil, where it had previously been heated by an open fire. They were not prepared to explain why that was so. The would not say that it made the whiskey worse, but that conservatism of the distillers was such that if there was an alteration of any sort in character they would want to go back to where they were originally.” Really interesting, direct fired pot stills are thought to produce a more complex product and that idea persists today. I remember coming across new literature that shows other reactions happening due to encountering super heated hot spots other than the production of furfural. I suspect that the distilleries were stodgy because they were trying to scale up, like increase production 10x, and, true they had new equipment options, but they want to keep their product as consistent as possible even thought it was in new vats and passing through new stills.  They new their character was valuable but they didn’t now exactly how they got it.

“As to the removal of rousers from a still, if that were done, it would be impossible to carry on at all because the burning and charring that would go on in the still would be so excessive that the whisky would actually taste not only of furfural but of burning. In the case of the brewer the wort was put into the copper without any yeast, etc., but the distiller was putting into the still a liquid which by comparison, was almost a semi-solid. It was carrying suspended yeast and other matters which came from the mash tun.” […] “therefore it would not be feasible to remove the rousers.” Here is a look at the rousers (stirrers) from the distillers prospective instead of the brewers prospective seen above.  If agitation by the rousers is so important, what I wonder is what did the distillates of tiny five gallon farm stills taste like if they had no rouser. Were the farmers straining their wash or how else were they tackling the problem?

furfural chartThis chart from the paper, which you unfortunately have to enlarge by clicking on it, has furfural statistics for a variety of very interesting spirits. I cannot interpret the data but it does point to new authors: Goot, Heron, Fernbac, Schidrowitz & Yeed.

Scotch / Pond Water / Floaties / Ammonia / Misc.

I have just come across two really amusing portraits of the Scotch Whiskey industry from 1926 and 1928. The first paper, which I will spend some time covering, was presented to the London engineers club by their author, S.H. Hastie, O.B.E., B.Sc. Since no one else likes to read the original material I will just extract the finer points and perform a little interpretation.  I really hope some people try reading the papers.  They are fairly accessible scientifically, have a really interesting historical context, and a really amusing comment section at the end.  I wish we still had presentations and clubs like these.  These guys were serious generalists and this really is nothing more than a gentleman’s understanding of chemistry.  Maybe this is how Tales Of The Cocktails should go?

I am not choosing to cover the entire paper but rather focus on some historical bits and Hastie’s explanation of water used in Scotch produciton.

Hastie 1926 for the London engineers club

Hastie 1928 presentation regarding a paper in the journal of brewing

“The following paper was read and discussed and a number of lantern slides were shown.” Lantern slides and probably a smoky room full of drunk, fat, well dress men. I bet there was at least one monocle in the bunch, the original steam punkers.  When the meeting broke they all left for the brothel.

“‘Character’ in whisky produced by the pot still process in the Highlands and Islands of Scotland is the term by which is designated the palate flavour experienced in tasting such whisky. It cannot be attributed entirely to the chemical substances found in whisky as reported in the conventional whisky analysis, nevertheless the distinctive differences between one pot still whisky and another is obvious to the consumer and is particularly definite to the expert.” I think he is implying that their chemical analysis is over simplified. For example they could only counter esters as acetic, they could not further subdivide the different esters.

“‘Character’ then may be defined as the palate flavour which each pot still whisky produces sufficiently definitely to permit of each whisky being differentiated from every other whisky. It is, further the criterion of quality used regularly in the selection of whiskies for introduction to blends with the object of meeting the palate demands of the consumer.” Hastie is very wordy and inarticulate and now you see why Hemingway was so important when he came out. Hastie does start to talk of supply and demand and mentions that some scotches have a character that is so high in demand that they command a significantly higher price despite have plants with material value and capital costs as another. You’d think the further you went back that people would be more interested in just getting drunk and they would even be less aware of their options. Maybe we’d have to go back another 100 years?

“The character of the whisky itself may remain, and does remain indefinitely the same, but the taste of the consumer varies from time to time, so much so, that the chosen drink regarded by one generation as highly palatable may become almost the poison of the succeeding generation.” This is the earliest mention of a swing in public taste I’ve ever seen. Previously I thought tastes were only noted as changing post WWI.

“Campbeltown, the birthplace of the manufacture of pot still whisky, now finds its product shunned by the consumer, and this change in public demand is such that this once busy centre of production is now rapidly becoming a lifeless locality so far as whisky production is concerned.” I don’t know the Scotch scene inside and out, but I’m under the impression that Campbetowns are only slowly returning to the market.

“Elsewhere, although public demand for whiskies with certain characteristics may not have reacted so drastically on the industry, in certain areas, there are still very material differences in market value between whiskies, entirely the result of the absence of presence of desirable characteristics.” So many of the new distilleries have a character that I don’t think is worth much money. There is the idea that no distillery really knows what they are doing and they can’t really call their shot in terms of character. So the market decides if they stay in business or go under.  Every new distillery is just a random shot in the dark as far as the success of their character is concerned.

“Pot still, or “all malt” whiskies, may be divided into four great classes: North East of Scotland (including Speyside), Campbeltown, Lowlands and Islay. These classes are altogether distinct in characteristics, whilst there is a class resemblance between whiskies produced in each of these districts of Scotland. North country whiskies are notable for a comparatively light, clean flavour, Islay’s are markedly heave in character, Campbeltown’s are known by a penetrating undesirable flavour, whilst Lowland malts are, compared with these other, comparatively featureless.” This is the earliest, fairly articulate Scotch differentiation I’ve ever seen.

“Indicative of the appeal to the public palate of Scotch whiskies from various districts of Scotland the Boston Daily Advertiser of recent date contains the following:–

‘A consignment of 400 gallons of ‘Ilay’ whisky from the Scottish Island of Islay was captured by the State Constabulary. The assistant analyst of the Health Department said, in the course of Court proceedings, that he had never heard of ‘Ilay,’ but that analysis showed this to be the best Scotch whisky out of 2000 brands which he had sampled.’

It would be interesting to know exactly how the chemist in question drew his conclusions from chemical analysis, as he appears to have done, without the aid of evidence of his palate.” I suspect the guy was teasing and he drank his share of the stuff. Back then there were people of “strange vantage points” [Amerine’s term for Peter Valaer of IRS fame] who analyzed or got to sample vast amounts of spirits from around the world.

“Two natural local factors must therefore be concerned, namely, the peat and the water supply, as no other essential factor locally existing is made use of in the industry.”

“The bored well of the brewer, supplying water comparatively rich in inorganic substances and free from organic matter, is the exact opposite of the distiller’s supply drawn from mountain or moorland loch, generally shallow and yielding surface water containing practically no inorganic matter but heavily laden with the vegetable organic matter derived from the peat and moss lands forming the catchment areas and the natural basins of such loch.” So they basically use pond water instead of well water! I’ve heard bits about Scotch water but I’ve never seen it contextualized like this.

“If the influence of the water used is a factor in the forming of character, then there must be fundamental differences either in the inorganic substances found in these waters or in the vegetable organic matter with which the water is so distinctly and so heavily charged.”

“There is a deep-rooted belief in the industry that all variations of character are due to the water, but explanation or proof does no seem to have been attempted, and if the facts are examined there is little real analytical evidence to support this belief.” Hastie goes on to provide a chart detailing the waters of Speyside, Islay, and Campbeltown.

inorganic chartInterestingly, Organic compounds are only subdivided into two categories because I think such things was beyond there analysis at the time. It might parallel the inability at the time to subdivide esters and other major congener categories. I’ve never seen any other research that identifies the special character of these scotches but I’m sure there are some modern studies somewhere.  Often modern studies just beat you over the head with lists from mass-spec/chromatography but do not assist the connoisseur in understanding how the compounds got there relative to other options. I haven’t read any modern books on Scotch so I don’t even know if these issues are dissected by great authors like Ian Buxton and his contemporaries.

“…and the reasonable deduction is that this vegetable matter is of paramount importance to the process since no group of these Highland distilleries employs a water which does not contain much vegetable matter while few of them employ water containing much inorganic matter. It must be concluded that this vegetable matter is the determining factor not only as to the suitability of a water for distillery purposes, but also as to the character of the whisky produced.”

“The technical difficulty is to determine what these individual substances are, how they differ, and what the specific effect of each is on the product. Science has surely seldom been faced with such a problem.” Scotch, at the forefront of early 20th century science!

“The effect of possible important differences in the bacteriological conditions obtaining in the different waters employed has been mentioned, but there is at present no evidence of any kind to support or oppose such a theory. It is difficult to believe that the races of predominant bacteria can vary to such an extent that organisms which have survived the mashing process still have such varied powers of altering the character of the product as to yield the different whiskies produced in practice.” I bet bacteria is killed but their bodies are still full of aroma precursors that could react is a variety of ways and contribute character. This is certainly the deep end of chemistry.  Small amounts of pungent, penetrating, acrid compounds like ammonia could definitely be the fodder of extraordinary olfactory illusions.

“The problem is still more complicated when the effects of these minute variables on the final product are considered, and can only be assayed, at present, by no more delicate a test than the palate of the expert taster of the whisky. Chemical analysis as at present employed is useless for the purpose. Hastie knew what he didn’t know and wasn’t afraid to say it! Mark of a good man.

Hello Mr. Hastie, why are distilleries located near such uniquely gross waters?

“The most reasonable explanation of the geographical distribution of pot still distilleries appears to be not the direct result of a definite choice for any technical or economical reason, but the result of a process of evolution. It may be safely presupposed that a natural desire for a fermented liqueur made from a cereal has existed for centuries and its origin is lost in the mists of antiquity. From early times the production of whisky has been a hazardous enterprise as a result of the pressure of authority upon the producer, so much so that remote and inaccessible sites were perforce chosen for its production. These circumstances resulted in the industry such as it was in early times being situated in the Highlands and Islands. Otherwise, it is reasonable to suppose that the site of operations would have been in the barley producing districts of the lower country, where all the raw materials, including fuel other tan peat, were available. If it be admitted that the Highlands became the natural seat of operations of the smuggler and of the illicit distiller from whom the methods of production have descended, then the obvious solution of the all important fuel question would be the naturally abundant peat, while the local water, whose character would undoubtedly be considered as of no consequence as a whisky character maker at that time, would certainly be employed, since the character desired consisted of a flavour of burnt peat and the bite resulting from an alcoholic strength well over proof.”

“By accident the local conditions round each distillery differed from these influencing neighbouring distilleres, public taste favoured certain individual products and these survived. In this way it seems possible to explain the geographical distribution of distilleries.” Here, Hastie restates my idea from above.

I’m at the end of your attention span and probably should leave it here because Hastie starts to talk of other topics besides water.  It is well know that water rolls through the peat bogs but what is new here, at least to me, is how he frames it against the well water option and that organic compounds would be nasties like ammonia and its relatives.

Anyone that reads Hastie’s original papers will be greatly rewarded. If you really enjoyed these papers I suggest you spent some time with the IRS researcher Peter Valaer who describes Cuban rum production pre-Castro among other great rum topics.