Distiller’s Workbook exercise 12 of 15

Marmite Aromatized Rye

The idea for the Marmite aromatized rye came while reading about the use of yeast autolysis in beverage production. Yeast autolysis is the process of dead yeast cells breaking down and contributing aroma which in some beverages can be considered a flaw while in others considered a feature. The aroma of the dead yeast is one of the things that makes expensive vintage dated Champagnes so highly regarded. In Champagne, the term mousey is often used for the contribution of autolytic yeast to the aroma. Eau-de-vies of autolytic yeast have an obscure tradition of being made in some parts of France and are often used for confections.

In the exercise, a commercial bottling of rye whiskey is re-distilled with an extract of autolytic yeast. Both Marmite and Vegemite, which can be found at many super markets, are essentially yeast extracts. Salt is used to break down the yeast cells releasing aroma as well as preserving. If either product is distilled, aromas can be captured and separated from the non-volatile salt. These salt preserved yeast extracts might draw some comparisons to what many people call dunder which is used to increase the aroma of rums in Jamaica. Dunder is spent yeast whose acidic aromas are locked up with alkaline lime marl as they go through aroma producing secondary fermentations. Eventually added back to the acidic wash, dunder boosts aroma, principally esters (What latently has been called dunder might have really been called muck in the early 20th century and intimate details of its preparation and use have recently surfaced in the old journals of the agricultural experiment station in Jamaica).

Most all full flavored distillates from fermented material are distilled on the lees. It should be pointed out when contemplating this exercise that distilling on fairly fresh lees is different that distilling with autolytic lees or even dunder. In Cognac production, the lees are often separated to prevent the wine from inducing yeast autolysis while they await distillation together where they are reunited. Only percentages of the lees, which have a tendency to settle to the bottom of the pot, are used because large volumes can cause scorching and the release of unwanted aromas.

Fairly fresh lees have been shown to increase important generic esters and reduce unwanted aldehydes. Even fruit eau-de-vies of astounding freshness and purity are distilled on percentages of their lees. Great work was done by Roseworthy Agricultural College mid 20th century to explain the value of lees distillation and Robert Léauté contributes some of the most articulate contemporary explanations.

Many people have aversions to Marmite and Vegemite, but that is mainly due to the dissonant salinity. The aroma of autolytic yeast can be classified as olfactory-umami which likely can be traced back to esters that form from long chain fatty acids. The intensely memorable salinity of yeast extracts can quickly re-orientate learned associations and for some people the aroma can quickly become olfactory-salty.

Familiarizing oneself with the potential aromas of yeast through the exercise can be valuable to the new distiller but the aroma must be contemplated with certain considerations. Autolytic aroma, however fun, can be considered ordinary rather than extraordinary and possibly represents regrets and missed opportunities. The extraordinary aroma of dunder is differentiated from that of ordinary autolytic yeast by its unique secondary fermentations. Aroma from yeast can be seen as lacking a sense of place because it can so easily be found anywhere and often overshadows the unique and singular qualities of source material like fruit or grains which distillers typically want to elevate and tease out. All the while as the exercise proves, yeast aroma has a time and a place, and with the new cocktail contexts that so many spirits are enjoyed under, begs to be explored.

Yeast aroma almost seems like new oak in regards to wine. Small percentages of new oak can definitely pull a wine together, but after a certain point it definitely overshadows other less attentional nuances. As we explored the exercise and increased the yeast aroma in our experimental spirits with Marmite, we found that we also needed to increase other attentional features like wood tannin which we did via our novel faux aging technique. Post distillation, over a span of many months, the spirit did seem to develop in complexity.

The brandy distiller Hubert Germain-Robin makes some observations on the subject of distilling with lees in his short book: Traditional Distillation Art & Passion that may be relevant to the exercise. Germain-Robin claims that fatty acids in the lees can react with copper and the product will come over into the distillate at the heads point in the run, but unfortunately he does not elaborate much further. We were never able to duplicate any of the observations Germain-Robin made while using large doses of Marmite instead of lees, but Marmite is a processed product and therefore could be altered in a way that makes it behave substantially different than a normal lees distillation scenario.

When distilling with high percentages of lees, Germain-Robin claims to observe copper salts being produced that he filters with a screen constructed of unbleached white toilet paper which implies that the product of the reaction is insoluble. What ends up being caught by the toilet paper turns out to be copper corrosion from carbonic acid as all the CO2 in solution is quickly expelled as the boiler heats up and the phenomenon is explained in the text Whiskey: Technology, Production and Marketing. Not all distillers use the old school practice of filtering the corrosion because it is insoluble and ultimately removed in the second distillation of double distillation.


750 mL rye whiskey (we used Old Overholt)

100 g Marmite

7 g tartaric, malic, or citric acid (optional catalyst)

Mix and re-distill together slowly on low reflux until the thermometer on the still reads 98°C. Going past 98°C may result in a cloudy distillate. Marmite does not seem to produce unpleasant cooked aromas.

Optionally, to synthesize the pH and non-volatile characteristics of an aged spirit, de-hydrate a volume of aged Bourbon proportional to the amount you want to fake age then reconstitute the resulting barrel essence.

Using your hydrometer re-cut the distillate to your desired proof with distilled water (recommended 80-90).


When these drinks were served to Anthony Bourdain he exclaimed “that’s devilish!” & “you know, I’m a real Marmite slut“.

Marmite Rye Sazerac

2 oz. Marmite aromatized rye whiskey

4 g non aromatic white sugar (or .5 oz. 1:1 simple syrup)

4 dashes Peychaud’s bitters

rinse of Absinthe

expressed lemon peel


Marmite Rye Manhattan

2 oz. Marmite aromatized rye whiskey

1 oz. sweet vermouth

2 dashes Angostura bitters


French 75

1 oz. Marmite aromatized gin

.25 oz. lemon juice

.25 oz. simple syrup (1:1)

3.5 oz. sparkling wine

shake the gin, lemon juice, and simple syrup, then double strain and top with sparkling wine

expressed lemon peel


Aromatizing gin with Marmite for use in a French 75 contributes the mousey aromas of fine Champagne without the expense.

Distiller’s Workbook exercise 5 of 15

This is the umpteenth draft of the fifth lesson in my Distiller’s Workbook. I started it as a book project with the idea of generating interest in distillation by showing a simplified form of it based on the re-distillation of tax paid commercial products.

Over time, the recipes have been elevated from merely low involvement cocktail-centric creations into being a workbook of exercises for new distillers to learn big concepts in distillation on small scale equipment with affordable batch sizes. Hopefully new distillers will be able to learn most all the what-if scenarios of operating a still so they can instead deepen their involvement with the sourcing & processing of raw materials, fermentation, and then the maturing of spirit.

A big focus of the workbook is to expose new distillers to the giant body of research concerning the subject via referencing it. I started by collecting every book on the distillation I could find and that still left a lot of questions. I eventually started collecting forgotten and seldom seen journal articles.  These were newly digitized or trapped behind pay walls and I have read hundreds in the last few years.  Most professional distillers do not even know this massive body of work exists so I hope to weave it into the content and introduce it to people.

Hershey’s Chocolate Bourbon

Cocoa aromatized Bourbon started simply as an attempt to get extraordinary aroma from an affordable source and ended up illustrating important concepts of aroma creation in the still. Cocoa powder, which will be added to bourbon and re-distilled, is high in butyric acid, a volatile fatty acid, which has the potential to react with alcohol and form an ester. Esterification is one of the most important aroma creation processes in distillation from fermented material. Ester creation influences many decisions when operating the still such as how time under heat should be varied, how fractions should be recycled, and how distilling material should be acidified to catalyze the process. Sophisticated distilleries count esters and their precursors with analysis tools like titration, chromatography or mass spectroscopy but this exercise is setup so that all changes to the spirit will be readily apparent through organoleptic analysis which is just simply by smelling.

Not all cocoa powders are the same. Each exhibit different tonal effects and some have more distinct rancio aromas than others. The rancio descriptor refers to both the olfactory-umami aromas which are a result of the roasting process as well as specifically volatile butyrates which are common cocoa powder additives. Butyrates are commonly found in milk products such as butter and Parmesan cheese. Butyrates on their own and in high concentrations can smell noxious and reminiscent of vomit, but in small quantities and in the presence of other sources of attentional tension, they can add exquisite complexity which is why they are so widely used as an additive. The boiling point of Butyric acid is 163.5°C, which is well above that of water, but its relative miscibility in water and ethanol makes it volatile during beverage distillation. The ethyl ester, ethyl butanoate, is even more volatile.

Feel free to execute this exercise multiple times and be patient. The final distillates can take months to mature, illustrating the slow but dramatic changes that happen to new make spirit post distillation. Also feel free to perform the exercises with variation so you can explore the influence of a specific variable. For example, run the still slowly one time to maximize time under heat while the next time run the still fast. Use the recommended acid catalyst or not. These are lessons that most distillers never get to learn first hand until they run a big rig and even then there isn’t always time and money to explore every what-if scenario.

When the exercise was first performed (distilled fast with no catalyst), the results were considered an inharmonious failure, but over time the aroma changed significantly in the bottle. At first the aroma was vomit-like due to above recognition threshold amounts of butyric acid, but over time butyric ester was formed pushing the aroma of the distillate back to something wonderful and recognizable as chocolate.

Esters are both formed in the still and broken up leaving a net amount. The best explanation of esterification at the molecular level, which helps explain the role of an acid catalyst, is from Peter Atkins in his chemistry primer for the layman, Reactions. Accessible explorations of esterification have also been done in the form of student projects at Roseworthy agricultural college in the mid 20th century and the early Scotch researcher S. H. Hastie tackled parts of the subject even earlier on. Each researcher studied double distillation in pot stills but from different (and not complete) angles. Roseworthy looked at the first distillation and saw a net accumulation of esters while Hastie began by working backwards, looking only at the second distillation and saw a loss of esters. The first distillation may see a net accumulation of esters due to high total acidity in the distilling material while the second distillation may see a net loss, but no papers seem to explain the whole story conclusively.

As the exercise illustrates, fatty acids that survive to the final distillate can even form esters post distillation. Certain equilibriums of esters exist as a function of the pH of the spirit and barrel aging, which lowers the pH, changes the equilibriums. A way to explore aspects of the pH impact on post distillation esterification is to use a novel fake aging technique. Samples of commercially produced and sufficiently barrel aged spirit can be put into a food dehydrator to remove the volatile fractions at fairly low temperatures. What remains is barrel essence which is essentially the perfect soup of non-volatile acids and tannins. The newly distilled spirit can be used to reconstitute the barrel essence and thus quickly take on the pH of an aged spirit. The spirit produced in the exercise can be divided in two with one portion being fake aged to lower the pH and one half left alone as a control. If done, the new distiller will have a small scale, slow motion, post distillation esterification kinetics experiment with a distinct fatty acid. The spirits should be repeatedly evaluated over time to observe the changes.


500 mL Bourbon whiskey (we used Evan Williams)
35 g cocoa powder (we used Hershey’s brand)
8 g tartaric, malic, or citric acid (optional acid catalyst)
250 ml water

Mix and re-distill together on low reflux until the thermometer on the still reads 93.33°C. Going past 93.33°C may result in a cloudy distillate. The extra water is added to reduce the chances of cocoa powder solids scorching on the bottom of the boiler.

Using your hydrometer re-cut the distillate to your desired proof (we recommend 90-100).

Optionally, to synthesize the pH and non-volatile characteristics of an aged spirit, de-hydrate a volume of aged Bourbon proportional to the amount you want to fake age then reconstitute the resulting barrel essence.

Try this exercise multiple times changing variables so as to produce comparisons and you will be rewarded.


cocoa aromatized Bourbon Sazerac
2 oz. cocoa aromatized Bourbon
4 g. non aromatic white sugar
4 dashes Peychaud’s bitters
rinse of Absinthe


cocoa aromatized Manhattan
2 oz. cocoa aromatized Bourbon
1 oz. sweet vermouth
2 dashes Angostura bitters

inverse Brandy Alexander
.75 oz. cocoa aromatized Bourbon
1.5 oz. Pineau des Charentes
.75 oz. cream (we enjoy heavy cream)

Barrel Aging / Rhetoric / Information Design

If this is your first foray into aging, why not do it from the perspective of an exotic tax scenario?

State Board of Equalization Office Correspondence, June 7, 1954

The above link is a correspondence related to a tax case from 1954 concerning barrel aging. The heart of the issue is whether barrels are a primary ingredient in the whiskey and should not be taxed or if as a vessel for storage they are just a manufacturing aid that rubs off a little and should be taxed. A lot of money was at stake and of late this is a timely topic due to a trend in barrel aged cocktails, a recent shortage or new barrels, and the very recent exorbitant value put on ultra aged American whiskeys by the nouveau riche finance crowd. These whiskeys are often criticized for their over extraction of compounds from the barrel–too much barrel as primary ingredient.

There are many accounts of the significance of the barrel on a spirit but I singled out this paper because of its audience of non scientist law makers and emphasis on organization to support its rhetoric.  This document is trying to be persuasive to a specific audience which is something I need better mastery of.  I need to think of myself as more of an information artist like Leonard Koren whose work I return to constantly.  The author explains to an audience of laymen, who back then had better understandings of chemistry than today, the basics then in last page, switches on his lawyer attack.  He has to bring his audience up to speed quickly and succinctly for them to catch and fall for the rhetoric of his last arguments.  Rarely does common spirits writing have such purpose.

The writer of the paper, John H. Murray, wants you to see barrel aging his way and at stake is millions of dollars of tax revenue.  My own accounts of science & art do not have so much resting on their shoulders and that lack of pressure probably hinders my ability to organization and persuade.

Just recently the idea of a barrel tax has come up again in Tennessee which targeted Jack Daniels.  At the time there was no tax on barrels, which implies there hasn’t been for a long time and probably all around the country, but the county desperately needed more revenue so they tried to impose a tax in a way that would target the Jack Daniels distillery specifically.  The county ended up losing to Daniels and unfortunately the case did not produce any great organized explanations of the barrel aging process. It did however value a reasonable tax on barrels at $10/barrel or $5 million a year for Daniels.  The Jack Daniels tax was not based on any philosophical point of view of the barrel relative to the final product, but rather just the right to impose an arbitrary fee to raise badly needed money.

Over the years, countless people have asked me varied questions regarding barrel aging and it has proven a hard topic to tackle unless you want to over simplify and dodge some science. I think this paper is a great, accessible, historic look at the topic and I hope people spend some time with the source document linked above.  I’m just going to do the usual and select some quotes so they are well indexed and then chime in with some extra background information.

“For this reason, taxpayer contends that the barrels are substantially consumed in the aging process, portion of the barrels become a component of the finished product, and therefore tax should not apply on the sale to them of the barrels.” So there is no tax on the corn but there is a tax on the vessels that the corn ferments in so are the barrels they age in like the corn or like the fermentation vessels?

They reference Changes in Whiskey While Maturing by A.J. Liebmann and Bernice Scherl and “a transcript from the conference of October 22, 1947, between representatives of Association of Maryland Distillers and representatives of the State of Maryland on the subject of ‘Tax on Whiskey Barrels’.” I cannot seem to find this transcript, but maybe some better positioned readers could help out?

“When once used these containers cannot be reused for the aging of straight whiskey. They may be used, however, for the storage of wine and other uses not connected with the aging of whiskey. Whiskey will not mature properly unless the charred oak barrel is new.” What I’ve been wondering about lately is how much fixed non-volatile acidity the whiskey soaks up on each filling.  The first filling no doubt can absorb a lot but does it diminish much during the second? pH is so much more important to aging than is commonly thought.

“The alcohol molecules, being larger, do not pass through the barrel at the same rate as the water molecules. For this reason, although there is some evaporation of water and alcohol during the aging process, the water evaporates more rapidly than the alcohol and the proof tends to increase.” This I think relates to humidity and some warehouses in other parts of world can actually lose more ethanol than water.

“Certain solids extracted from the barrel contain acids and are responsible for the reddish brown color of the matured whiskey.” These acids that get absorbed are also responsible for the equilibrium between esters and fatty acids that form. Acids might have been added to faux whiskeys back in the day to synthesize the acids that would have been accumulated during time in barrel.

“During the early stages of the maturing period there is a rapid increase in total acidity. This may be due, in large part, to the extraction of materials from the barrels. Fixed acids, that is acids in the solids, increase rapidly during the first 12 months of the aging period. Liebmann and Scherl state that the entire fixed acidity normally is due to the extractions from the barrels.” Another thing I’ve been wondering after drinking quite a few bottles of the Renegade rums, which were well aged then finished in wine barrels like Madeira, is whether finishing barrels can significantly bump up the acidity of a spirit. I was lucky enough to spend a lot of time with the whole Renegade series and each had an acidic tang like no spirit I’ve ever encountered.

“The acid content is responsible for the ‘tang’ of aged whiskey.” I don’t believe many people think of aged whiskeys like Bourbon being tangy because the word sweet gets thrown around so often instead.  Imbibers these days articulate and differentiate between relative sweetness but not relative tang. What is strange on a sensory level is that the tang is an authentic gustatory sensation while the sweetness is often an illusion due to sensory convergence with olfaction where prior co-experience allows you to categorize olfaction in terms of gustation and link the separate modalities so strongly it feels like genuine synaesthesia.

“During the aging process there is a fairly steady increase in the ester content. This would indicate that the esters are probably formed chemically during that process.”  Esterification continues to happen as the pH drops because acidity is a catalyst in the reaction between free fatty acids and alcohols. Supposedly pH drops rapidly at first then levels out and continues to decrease proportional to the angel’s share changing the volume.

“During the first 3 years there is an increase in aldehydes, but after that the rate of increase levels off. That is, aldehydes are probably produced by chemical reactions during the aging process.” Aldehydes, at the moment, are a large hole in my knowledge of congeners.

“During the early months of the aging process there is a rapid increase in furfural. Newly made whiskey does not contain this substance and apparently it is extracted from the barrel since furfural is formed in the process of charring wood.” This is not the whole furfural story. Furfural is also a product of direct fire heated pot stills due to the degradation of pentoses.  Furfural ends up in the tales of the distilling run and is mostly cut away.  Esters and aldehydes and higher alcohols are commonly subdivided in analysis but furfural is something that I do not know much about its sub divisions. Is the furfural accumulated in the barrel much different than furfural accumulated in the pot still?

“Fusel oil (higher alcohols) constitutes an important component of whiskey as far as character and quality are concerned. Its content is dependent upon the method of distilling used. There is very little change in the fusel oil content during the aging period and apparently any increase is due to the increase in concentration by reason of the evaporation of water and alcohol. Some of the esters may be produced by an interaction of the various constituents of the whiskey and the fusel oil.” The majority of esters are from ethanol linking to fatty acids but esters can also be formed by higher alcohols linking to fatty acids. A few of these higher alcohol esters are considered flaws in large concentrations and are more likely to form in column stills because of the tendency for higher alcohols to accumulate in certain plates within the column which the fatty acids have to pass through. I think the banana aroma of goslings rum is due to a higher alcohol ester.

“The solids contained in whiskey are derived entirely by extraction as are the tannins. The solids apparently affect color, the tannins the acid content.” Tannin is acidic but I suspect there might also be more acids at play though I cannot name any off the top of my head.

The paper cites IRS chemist extraordinaire Peter Valaer from “the conference between the Maryland Distillers and the tax representatives of that State […]”

“During the aging process the percentages of substances other than ethyl alcohol and water increase by about five times.” Pretty high! Makes you wonder when the rhetoric starts and what side he is gong to be on! Tension building..

“The aging process, he indicates, consists of the extraction of some of the materials from the wood and the interaction of some of the acids on each other producing esters and at the same time alcohol is oxidized producing more acid. The aging process consists of a series of those changes. He is of the opinion that about one-half of the congenerics in the matured whiskey are produced by changes taking place in the barrel and the remainder are extracted from the barrel. The body of the whiskey is determined by the fusel oil content and without it the whiskey would have no character.” So here we have a summary of the opinion of the most privileged spirits chemist of the era. An astounding amount of samples from around the world came through Valaer’s IRS laboratory for analysis and he even pioneered numerous analysis techniques.  Valaer seems to paint a picture of the barrel as ingredient but then the fusel oil content, which is not a product of the barrel, contradicts it? So far it is still difficult to figure out the author’s stance.

“From the foregoing it would seem logical to draw the following conclusions:” From here I retyped the complete remainder of the paper which is more or less the last page.

“The maturing whiskey in charred oak barrels is one of the steps in the process of producing a marketable whiskey. The type of whiskey and much of its flavor is determined by the type of mash use, fermentation process, and method of distillation. Newly distilled whiskey is colorless and unpleasant in aroma and taste. The maturing process in the charred white oak barrels results in some of the higher alcohols and fatty acids being absorbed by the char eliminating some of the unpleasant characteristics that these substances would otherwise impart to the whiskey (Encyclopedia of Chemical Technology, Volume 1).” Here he paints a picture of the barrel as a filter which would be a manufacturing aid.

“The whiskey attracts from the barrel various solids and other matters which give it its characteristic reddish brown color and also extracts some furfural which may affect the body of the matured product.  The fusel oil which primarily determines the body of the whiskey is present in the whiskey from the time of distillation. Some acids are extracted from the barrel, other acids are formed in the barrel by oxidation of the alcohol and by interaction of the various substances upon each other esters are formed. These esters affect the odor of the whiskey and give it a distinct fruity odor. During the entire aging process the barrel acts as a semipermeable membrane allowing the evaporation of water and some alcohol and the introduction of oxygen into the material through its small pores. In this way the barrel and the charred interior act as a catalyst aiding in the various chemical changes which take place in the whiskey.” I feel here that he is breezing past and downplaying the importance of the compounds added by the barrel. And again fusel oil, which is not from the barrel, gets over emphasized. His stance is becoming apparent.

“It is readily apparent, therefore, that the barrel serves a distinct purpose as a manufacturing aid in the maturing of the whiskey. It acts as a container for storing whiskey during that period, its semipermeable natures makes possible the complicated series of chemical reactions which take place during the process, and the extractives from the barrel give the whiskey its characteristic color and impart to it some of its flavor. Thus, minute portions of the barrel become an important part of the finished product.” Readily apparent, what rhetoric! This again downplays the extracted compounds and their role. It also down plays their weight as a percentage of the congeners which a dissenting opinion might emphasize and requote Valaer.

“If the only purpose of maturing the whiskey in the charred oak barrel were to add to it the tannins, the furfural, the solids, and the color, the use of oak barrels would be an extremely expensive process to impart to whiskey certain chemical compounds. These compounds could undoubtedly be added mechanically much cheaper and easier. But the function of the barrel is much more important than merely imparting to the whiskey these compounds. It is used to store the whiskey and to aid in certain chemical reactions the end result of which produces a matured pleasant tasting beverage. This would seem to be the primary use of the barrels and accordingly the barrels are primarily manufacturing aids and are considered subject to tax.” Silver tongued devil!

“Perhaps we can draw an analogy to the iron balls used in the grinding of cement. During the grinding process a portion of the iron in the balls wears off and becomes a component of the cement. Iron is a necessary ingredient in the production of high quality cement. The iron balls thus contribute in two ways to the manufacture of cement (1) by grinding it to a powder and (2) by imparting to it at least a portion of the required iron content. Nevertheless, the iron balls are manufacturing aids and are considered subject to tax.” What an analogy! If I didn’t know better I’d almost be seduced myself.

“In 1948 A— D— Company sued the State Board of Equalization in Sacramento Country to recover some $X,000.000 tax on its purchases of charred oak barrels used to contain and mature its whiskey. The primary contention there made was that the barrels were sold with the matured whiskey and consequently were nonreturnable containers and exempt from tax. The court discussed the use of the charred oak barrels in the processing of the whiskey and indicated that the barrels were used for a purpose other than retention, demonstration or display and that such use was sufficient for the imposition of tax. The court did not pass on the question of whether the barrels by reason of the absorbtion by the whiskey of a portion of their content became a component part of the finished product and thus exempt from tax.” Here he discusses a related case where they try to categorize the barrels as non returnable packaging. This makes me wonder if part of being a manufacturing aid requires a higher degree of re-usability?

“Taxpayer presented a letter from the State of Maryland which indicated that the Maryland Controller had ruled that distillers could purchase new cooperage to be used for the aging and curing of bonded whiskey tax free. The basis of this ruling is not apparent from the letter.” Any legal scholars available to find more information on this Maryland case?

“It is recommended that the petition for redetermination be denied.”

If you wanted to argue it in the other direction what other evidence would you use and what other analogies would you present?

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.”


In chemistry for budding food scientists, Peter Atkins is your Virgil.

One of the great books I’ve come across lately is Molecules (1987) by renowned educator Peter Atkins. I came across the title as a curious entry relative to the others in the back of Neurogastronomy. I figured it was selected for a good reason and looked it up. Wow. The book was so ahead of its time and gives a very intuitive look at chemistry. Atkins continuously touches upon subjects near and dear to me which are food chemistry and plastics chemistry. I thought I would just reference a few things, but I ended up reading straight through.

Molecules is really exemplary science writing and Atkins continuously manages to be edu-taining by saying memorable, often funny things that help to retain the material. He infuses his explanations with an Nth degree drama.

Samples from Molecules:

“There is delight to be had merely by looking at the world, but that delight can be deepened when the mind’s eye can penetrate the surface of things to see the connections within.”

“I tried to avoid technical terms throughout, but some inevitably (or at least unintentionally) crept in and are explained in the Glossary. Where possible, I also tried to explain. But do not expect too much fulfillment here, for some explanations are not yet known to anyone, and others require too much technical background. Moreover, I did not want to diminish delight by overloading the text with too much explanation: this is only an introduction to understanding. I particularly wanted to show that some appreciation of the features of molecules can be achieved without a college degree (or even a freshman course) in chemistry.”

(Just before benzaldehyde, Atkins explains the lock & key mechanism of how odors interact with odor receptors. I think this section is why Neurogastronomy referenced it)

“Benzaldehyde (103) C7H6O

Hydrogen Cyanide (104) HCN

Benzaldehyde is a colorless liquid that smells of bitter almonds. A closely related molecule, phenylethanal, is obtained conceptually by inserting a -CH2- group between the benzene ring and the -CHO- group. This latter molecule fits a floral receptor better than benzaldehyde itself. It smells of hyacinth and is used in perfumes under the name hyacinthin.

Hydrogen cyanide is an almond-smelling, colorless, poisonous gas with an odor that fades on prolonged exposure. […

…] The aroma of cherries and almonds is due to benzaldehyde, but the hydrogen cyanide in cherries, also contributes somewhat. Benzaldehyde and hydrogen cyanide both occur quite widely in drupes and pomes (multiple seed and single-pit fruits), especially apricots and peaches. They are released when the pips are crushed and enzymes can get to work. This much the Romans and Egyptians also knew, for they ground peach kernels to make poisons. [….]”

“Isoamyl Acetate (105) C7H14O2

Ethyl 2-Methylbutanoate (106) C7H14O2

With these two molecules we see nature building different compounds in similar ways and from the same kit. The isoamyl acetate molecule is an ester formed from acetic acid (32) and an alcohol, isoamyl alcohol. The ethyl 2 methylbutanoate molecule is also an ester with the same numbers of carbon, hydrogen, and oxygen atoms, but they are bonded in a different pattern.

Both compounds grow in prominence as apples ripen and, as their concentration increases, they mask the characteristic flavor of the unripe fruit. Esters with about seven carbon atoms have characteristic fruity smells, occur widely in fruits, and result from the breakdown of long-chain fatty acids (35) as the cell membranes are oxidized during the ripening process.”

I enjoyed Atkins approach so much to a topic commonly thought mundane that I plunged into another of his titles, Reactions (2011), where he guides you through the “private lives of atoms” via an engaging Dante/Virgil guided tour sort of relationship to the underworld.

Reactions is chock full of tours (maybe more like journeys) that are directly related to many things I’ve been working on, particularly distillation. Atkins explains acid/base reactions in a way I’ve never seen before. He covers the unique qualities of water that make it so reactive in a way I’d never experienced in two years of high school chemistry (hydrolysis!). Most specific to things I work on, Atkins covers esterification reactions and explained how acids participate as a catalyst. These two texts will greatly aid distillers and wine makers who want to deepen their involvement, help you to be able to read and understand journal articles, and just finally understand what the fuck all the “reduction” wine makers obsess over is about.

Again, Atkins constantly says ridiculous things, the kind of stuff you expect from your favorite teacher who is trying to enliven a dry text. He is a master of amusing puns and I found myself jotting down bits of his sense of humor to recycle as cocktail names (blunderbuss affair!). Atkins truly becomes your Virgil and is the best possible tour guide to a world many dare not enter.

I consider these two titles to constitute a gentleman’s understanding of chemistry and should be requisite reading for anyone striving to be a generalist. The titles may even be read not for the content, but just for their exemplary form. Every daunting subject needs a Peter Atkins.

“Chemistry is thought to be an arcane subject, one from which whole populations seem to have recoiled, and one that many think can be understood only by the monkishly initiated. It is thought to be abstract because all its explanations are in terms of scarcely imaginable atoms. But, in fact, once you accept that atoms are real and imaginable as they go about their daily lives, the theatre of chemical change becomes open to visualization.”

Wonderful stuff.

The Influence of Distillation Methods on Brandy Composition (1939)

Graham, W. O. Influence of distillation methods on brandy composition.  Australian Brewing and Wine Journal 58(6):40-42; (7):31-33; (8):26-31. 1940. (part I PDF link)

Graham, W. O. Influence of distillation methods on brandy composition.  Australian Brewing and Wine Journal 58(6):40-42; (7):31-33; (8):26-31. 1940. (part II PDF link)

[Unfortunately the first scanning of the paper was missing the last three pages but the second link provides all of the last segment: (8):26-31. Much thanks to the wonderful people at the Brookline Public Library.]

This was the last English language paper that I needed from Amerine’s Commercial Production of Brandies (1941) to complete his bibliography.  The journal article, it turns out, was a summary of a graduate thesis from 1939 and published as part of an award. (Karl Weidenhofer Prize for the best individual study or project submitted by the Diploma Class for 1939.) W. O. Graham’s topic was also influenced by the global conflict which would grow into World War II.  He thought Australia couldn’t compete well in the global wine markets so they should try to do more with brandy.  Australia already had many brandy producers but all where producing unremarkable low quality products.  Australian brandies were limited, not just by their source material, but also by techniques used to operate the still which was the focus of the study.

When I have time I’ll try to do a better review and extract some choice quotes.  This study, because of its limited scope, is perfect for home distillers to read.

It turns out W. O. Graham was Walter Osbourne Graham and he was top of his class in 1939 with two honors.  Roseworthy Agricultural College got absorbed by the University of Adelaide but they keep impeccable records.  Graham’s student project among others are digitally indexed but contained in manila folders somewhere in the library.  (Maybe we could convince them to make scanning of a few!)

Below is a review of the paper I had found in another old journal in case anyone is interested. I don’t think it does it much justice.  It would be awesome to see the original study.

“Influence of Distillation Methods on Brandy Composition. W. O. Graham. (Australian Brewing and Wine J., 1940, 58, No. 6, 40-42; No. 7, 31-33; No. 8, 26-31; J. Inst. Brewing, 1940, 46, 326.)–The proportion of secondary constituents (especially esters) is lower in Australian than in French brandies. The difference is partly due to the removal of a large heads portion (in which the aldehydes and, still more, the esters are concentrated) in the Australian distillation. Also, heads from a previous charge are not included in the Australian process, and the more rapid distillation in that process further increases the concentration, in the early fractions, of esters and of volatile acids. The volatile acidity of the original wine apparently has little effect on the ester-content, but esters do not necessarily increase during storage. With rapid distillation the alcoholic strength of the early fractions decreases very slowly.” E.B.D.

From Free Fatty Acids to Aromatic Esters: Esterification in the Still Made Simple(r)

Sponsor my distilling work simply by sharing the artisan workshop of the Bostonapothecary on social media. Copy, Paste, Support!

[More important than esters is the mysterious congener class often referred to as rum or Cognac oil and I have unraveled its mysteries in other more recent posts. Decisions made to maximize rum oil will also maximize noble esters. Esters can be faked in contrived ways while rum oil is still divine (though that may change).

Please feel free to comment and tell me I’m wrong or ask me to clarify anything. This post will probably be edited frequently and many of the comments will precede the edits.

This is an excerpt from the book on distillation I’ve been working on forever now. I’m trying to re-frame the text in a way that explores and emphasizes three main concepts:

1. Distillation is simple or fractional. Simple distillation is the separation of the volatile from the non-volatile while fractional distillation involves the further subdividing of the volatile.

2. Distillation is non-equilbrium like a pot still or can approach equilibrium such as in a column still. Volatility is effected by more than boiling point and the relative miscibility of a substance in water or ethanol can make something with a boiling point higher than water extremely volatile.

3. Aromas are either created in the still or not depending on the presence of aroma precursors. Many fractions are recycled not only to salvage alcohol but also to allow more time under heat to turn aroma precursors into aroma compounds.

One of my goals was to give an introduction to the topic and some general advice for distillers of low levels of involvement. Many of the ideas are speculative. I was hoping to shed light on the science just below the surface of many distilling rules of thumb.

It is a complicated topic full of tangents but I kept it down to 2100 words!


Many of the most revered aroma compounds are born in the still. Under certain conditions with the right precursors to feed the various processes, significant amounts of new aroma compounds are formed. The main process of aroma creation is esterification where free fatty acids react with alcohols under heat to form esters. Esters are very volatile and their fatty acids precursors are also volatile, even though they have boiling points higher than water. Many fractions of the distillation process are recycled into subsequent runs to give more opportunity for esterification. The recycling phenomenon means that you cannot just produce one batch of product because the final distillate is actually the product of many integrated batches. Aroma creation is not always maximized and restraint is often practiced to produce an elegant spirit. Pot stills are highly regarded for their ability to create new aroma compounds but if column stills are operated with certain methods of recycling fractions, they can also produce very full flavored high ester spirits.

Many processes are responsible for aroma creation but likely the only process that can be controlled to any significant degree during still operation is esterification. Other processes like maillard reactions, hydrolysis and oxidation are definitely important but when it comes to handling the still, they are likely just byproducts of decisions made regarding esterification [there are minor problems with this claim]. Full flavored spirits in pot stills differ from column stills by how the byproduct processes happen [I’m slowly learning the chemical ins and outs of articulating this]. If a pot still and column still were operated in such a way as to end up with the same ester content they would differ greatly in compounds created by other minor processes and the pot distilled product would likely be regarded as more complex.

To get esters to form in the still, the distilling material needs free fatty acids as precursors. Some source material is higher in fatty acids than others and some fatty acids are more noble than others. For example, apple varieties differ by fatty acid content with the higher being better suited for distilling material. The same is true of grapes. Not all esters are formed in the still or during fermentation. Esters are often already present in the source material and typically the higher the better. In fruit, esters form by enzymatic processes during ripening, more form by fermentation, even more form in the still, and believe it or not, even more form in the barrel. High total acidity in the source material often correlates to both high ester contents and high fatty acid contents which is why the wines of Cognac can yield a product with a higher ester content than the acid deficient wines used for California brandies. [What I’m missing here is that at the same time esters are forming they are also breaking up due to hydrolysis but at a different rate, often they even reform. The first distillation, due to its significant total acidity, may be characterized by a positive net ester formation while the second distillation which has no significant non-volatile total acidity (to catalyze esterification) is characterized by a net loss of esters. What I need is better research papers to support this. Most research projects only look at the first distillation and none (known to me) compare and contrast the processes at work in each distillation of double distillation.]

Yeasts are big sources of fatty acids and a percentage of the lees are retained in distilling material to produce esters from those fatty acids. Most full flavored spirits do not incorporate all of the lees due to off aromas produced as a result of having too many solids in the still. If there are too many solids there is a tendency for scorching. The relatively ordinary aromas produced from the lees may also overshadow the singularity and terroir of the source material. Some traditions exist of making brandies from accumulated amounts of left over lees but these distillers likely have stills designs to handle high concentrations of solids such as the steam jacketed stills used for grappa production or “rousers” which continuously stir the distilling material. [A big thing this misses is how distillation on the lees traps certain non-desirable congeners possibly through a fixative effect of reducing their volatility.]

High total acidity in distilling material may be important to catalyze esterification during the first distillation phase of double distillation in a pot still. There are many approaches to having a high total acidity as seen in high ester spirits like Cognac, Bourbon, and Jamaican rum. The wines used for Cognac are naturally high in total acidity which might be why Cognac distillers have always favored slow double distillation in a pot still as opposed to a column still. California brandies may have opted for a column still because they never had enough total acidity to justify the extra time and fuel expense of a pot still.

Distillers of Bourbon increase the total acidity of their distilling material with the sour mash process where a portion of the non-volatile fraction of the first distillation phase, often called backset, is recycled into the next fermentation. The sour mash process has the three fold effect of increasing micro-biological stability, recycling fatty acids, and inducing acid-catalyzed esterification in the still.

The use of dunder to make high ester Jamaican rums is very similar to the sour mash process. Dunder is the non-volatile fraction of a sugar cane fermentation after distillation and characterized by high acidity. Molasses is so concentrated a sugar source that significant amounts of dunder can be used to bring the sugar content down to a reasonable level. Dunder can represent as much as 50% of a molasses based wash for a high ester style of rum. Sugar cane is deficient in acids so Dunder is further acidified with sulphuric acid. The high total acidity creates slow, inefficient fermentations where secondary bacteria produce numerous extra aroma compounds [I have recently learned many of the finer points of this and attached the evolution of dunder’s use to some first name and specific dates). In the 19th century, high ester styles of Jamaican rum were produced as concentrates for exportation which would be diluted with relatively neutral spirits before bottling. The distilling material used for high ester Jamaican rums may have had 2.5 times the total acidity of the wines used for Cognac. Such high acidity would likely shorten the lifespan of a copper boiler but it is unknown (to me) whether Jamaican distillers used copper or wooden boilers [wooden boilers and I’ve found more specifics on that!].

Another idea for increasing the total acidity of distilling material to catalyze esterification is with freeze concentration also known as jacking. Freeze concentration, which is sometimes called freeze distillation or fractional freezing, separates compounds by melting points. Distilling material that is freeze concentrated ends up higher in alcohols, aroma compounds, and total acidity.

Ciders are known to have been freeze concentrated and the process may have given early American cider brandies the name Applejack. There is no clear historical references to ciders being freeze concentrated before distillation, but it seems likely that it was practiced if inadvertently. Ciders were probably distilled later in the winter when there were less farm chores to be done and by that time casks of cider stored in the barn would start to freeze. Ice crystals would form on the top which could be separated and a zingingly tart, higher alcohol beverage would result. Supposedly, concentrations as high as 30% alcohol can be achieved. The elevated alcohol content may have even negated the need for a second distillation. Freeze concentration before distillation was rumored by the mid 20th century flavor chemist Joseph Merory to create the highest quality fruit eau-de-vies, but no explanation of the underlying science accompanied his claim and it is not known if any commercial producers use the technique. The increased total acidity that results from freeze concentration likely increases aroma creation in the still through acid-catalyzed esterification.

Each phase of double distillation in a pot still is carried out slowly to maximize esterification [this may not be true if the second phase can be characterized by a net loss due to hydrolysis]. Applying too much energy can result in super heated hot spots in the boiler. Hot spots may break down yeast cells and reducing sugars generating favorable aroma compounds, but too many may also create off aromas by scorching. A pot still is thought to operate at non-equilibrium because there is no reflux beyond what naturally condenses on the walls of the still, but running the still too fast by increasing the energy applied to the boiler has been observed to change the distribution of the fractions. The observation may be the result of super heated hotspots volatilizing components in unpredictable ways [This is incorrect and the real reason is that reflux, due to the shape of a pot still, is more significant than you’d think. Run the still too fast and you challenge that natural reflux thus altering the fractions.]. Avoiding hot spots with a slow distillation may increase the predictability of fractions and therefore also increase product consistency. [Not challenging the natural reflux of the pot still in the second distillation will lead to a higher proof product and thus less spread out congeners and therefore opportunity for a larger hearts section.]

Not all fatty acids form esters in the first run. Often more time under heat is required so many of the fractions that are separated are recycled in the next batch. When you consider the linkage of batches, double distillation in a pot still ends up employing more fractions than people think and distillers often use various names confusingly. To understand double distillation it is useful to consider where every fraction ends up and why.

The first phase of double distillation in a pot still, often called a stripping run yields a foreshots (this term has different meanings historically) fraction that is discarded, a heads and tails fraction that are both recycled, a hearts fraction that is passed on to the second distillation phase and a non-volatile fraction that is often employed to recycle fatty acids that do not volatilize and to increase the total acidity of the next fermentation.

Under non-equilibrium distillation, what appears in the very beginning of the run can change significantly depending on the alcohol content. Besides above recognition threshold amounts of ethyl-acetate and acetaldehyde (that smell like nail polish remover) as well as methanol, the discarded foreshots of the first phase of double distillation may contain a lot of fusel oils that eventually move to the tails of the second distillation where the starting alcohol content is significantly higher [The foreshots may even contain very high boiling point fatty acids that physically clung to the condenser, but are dissolved by the high ethanol content of the beginning of the next run. This residue become significant when a still is shared across different product categories.). Fusel oils do not benefit from being recycled and are often only desired in low concentrations. Fractioning is used to separate fusel oils but they are also limited by manipulating fermentation variables to minimize their production. Fusel oils are the byproduct of stressing yeasts so distilling material is typically fermented to much lower alcohol levels than yeasts are known to produce in theory.

Not all distillers make a heads and tails cut during the stripping run. Some opt to pass everything along to the second distillation which might be due to a lack of involvement. The first phase of double distillation sees much more time under heat than the second phase as well as contains significant acidity to catalyze esterification so separating fractions high in aroma precursors and recycling them to the next batch’s first phase may result in the best opportunities for aroma creation. Some distillers only opt to return a portion of these heads and tails fractions to the next batch. These distillers are not trying to create the fullest flavored spirit possible but rather something elegant and refined.

During the second phase of double distillation, the alcohol content of the distilling material is much higher and all the non-volatile acids have been separated leaving nothing to catalyze esterification. Esterification continues to happen to fatty acids that have made it over into the second phase [Esterification continues, but so does hydrolysis which breaks up the esters and there may actually be a net loss of esters but no literature states a rule of thumb for what happens to ordinary esters versus more desirable extraordinary esters]. The increased alcohol content increases the rate of esterification in a way that may partially make up for the lack of significantly total acidity. The second phase is separated into five fractions. A foreshots fraction is discarded while a heads and tails fraction is taken and a percentage recycled during the next batch’s second phase. The hearts fraction becomes the final distillate while the non-volatilized fraction is discarded. The non-volatilized fraction of the second phase which is mostly water also likely has a lot of congeners in common with the foreshots of the first phase.

When cuts are made and it is decided how much of the heads and tails fractions will be recycled or discarded, it is important to note that not all fatty acids and their esters are created equal. They are definitely not all desirable. The esters of longer chain fatty acids are typically more desirable than the esters of shorter chain fatty acids like acetic, lactic, and butyric. Cutting a spirit will often involve separating undesirable shorter chain fatty acids and their esters, but like the higher alcohols, many of these components are better controlled and minimized by manipulating fermentation variables.

A column still also has many options to generate aromas in the still by the continuous recycling of small fractions that are high in aroma precursors. Once the still comes close to equilibrium a fraction that is high in volatile fatty acids is isolated and recycled through the column to increase its time under heat. A column still can increase the time under heat of small fractions while not investing in heating the rest of the volatile fractions which saves significant amounts of energy. The juggling of small fractions can produce large amounts of esters but the process becomes detached from other secondary aroma creation processes that typically happen alongside esterification during a slow double distillation in a pot still. [I don’t know how to explain this relative to the simultaneous esterification/hydrolysis phenomenon. I suspect the the fractions are relocated to a part of the column where alcohol is particularly high favoring ester formation over ester break up. Where alcohol is particularly high there is little water to break up the esters.]

Believe it or not, fatty acids have the potential of escaping esterification and making it all the way to the barrel. Barrel aging presents yet another opportunity for esterification (or even the breakdown of esters and other aroma compounds), but some distillers choose to remove many fatty acids by filtering through activated charcoal or using the chill filtration process. Untreated spirits have the potential to become cloudy upon dilution which many consumers are thought to object to. Particularly high fatty acid contents can also cause the distillate to appear cloudy after either phase of double distillation in a pot still.

Following the path of aroma precursors and their reactions can help distillers make more sense of the various fractions and where they end up. The extent to which fractions are recycled illustrates how integrated production runs are. Understanding the various options for operating a still when new aromas can be formed provides a basis for the experimentation required to sculpt distillates. This look at aroma creation is probably oversimplified by focusing on fatty acids and esterification as there are so many other reactions.  Esterificaiton is just a starting point and eventually as involvement deepens distillers will eventually build an understanding of the other aroma creation processes.

Creating beautiful spirits is more than just operating a still.  Aromas born in the still, whether a fault or a feature, have precursors that can be traced back to fermentation variables or the source material. Reasonable guidelines for operating a still will free the distiller to take a deeper look back at fermentation and then eventually a further investigation of the source material, be it grains or grapes. Extraordinary aroma born in the still comes from extraordinary precursors. So many variables may be daunting, but that is why spirits are so revered and so special. Exploring the potential for aroma creation from selection of the source material all the way to bottling may help small distilleries create new classes of full flavored spirits which allow them to differentiate themselves from larger distilleries making more restrained styles of spirit. Awareness of all the considerations that go into producing a full flavored spirit will certainly increase appreciation for the work of any deeply involved producer.

[edited to add: One things this post doesn’t do is differentiate the common esters. In another post I spend a little bit of time musing about the most generic of esters, ethyl-acetate which is not widely understood. I connect this congener to the threshold idea where for some reason we want as much of it in a spirit as we can without recognizing it. This can be said as we want it above the absolute threshold but below the threshold of recognition. Understanding these thresholds might teach us about the distillation of highly aromatic spirit concentrates that eventually get blended down. Certain terroirs of sugar cane or grapes or even certain apple varieties from a diverse orchard might be treated differently during production to maximize aroma. These concentrates cannot stand on their own but have to be blended down to keep certain key generic congeners in check. I haven’t found any great literature that specifically explains the concentrate idea so I’m just musing about it in theory.

Another ester issue of note that can differentiate the pot still from the column still is that because higher alcohols tend to stratify and bunch up in a column, more esters of higher alcohols have the opportunity to form such as amyl esters which are undesirable and considered flaws.]