Australian Rum Oil and reisling TDN?

[By the end of the post, connections start to be made that I didn’t have a good enough memory to make from the beginning. The existence of this paper was a tip from a particularly smart reader. The punchline may be that components of the mythic rum oil may come from at least two channels. The first is the splitting of glycocides by the enzymatic activity of yeast while the second may be from carotenoids present in the cane itself. Tons of work still needs to be done, but these are some good preliminary guesses of where to look. At the very least, they may point to realizing more terroir in rum, molasses based or otherwise.]

Here is a unique paper, Less Volatile alcohols Esters and Hydrocarbons in a Raw Australian Rum, 1975 (Bundaberg!), which may have a follow up if ILL can track it down. [The follow up is A new approach to the identification of flavour components in rum from the Australian Wine, Brewing, and Spirit Review, 1973. This brief paper was in the bibliography of the other and offers a great summary of what will follow.]

I read this after reading two different modern rum-GCMS papers which were kind of useless for the purpose of learning more about rum history or production. I’ve been aiming to highlight a unique thesis I found with some fantastic explanations of the evolution of chromatography, but I’m short on time and I think I may contact the author first to ask some questions.

In the paper, D.A. Allen reads two early (1966, 1970) rum-GCMS papers and wants to play along, but doesn’t have access to the same equipment. The authors used pentanes to extract congeners from very small samples of rums then analyzed them with GCMS to name volatile components. I’ve actually played with pentane extraction to produce artful creations, but that is another story for another day. Allen could not work with such small samples so he comes up with the novel idea of collecting fusel oil from the side stream of the Bundaberg production then toying with it. Allen’s idea is comparative to that studies that inspired it because most of the unique compounds everyone is looking for are less volatile. The paper ends a little bit abruptly, but he ends up finding the notorius reisling congeners TDN.

I’ll try to describe a little bit of the experiment, but what I should first note with disappointment is that Allen never organoleptically describes anything he is working on. Is he working with that peculiar, wonderful, desired rum oil or is this just low volatility junk? We never really find out here, but maybe we will in his other paper. The whole significance of this paper becomes the old fashioned extraction procedures he uses which may help the contemporary small scale fine producer. Another new possibility is that rum oil congeners may have appreciated in value enough (with our new found fine market) that it is now economically viable to harvest them from a formerly discarded fusel oil fraction. Maybe it is already done for the fragrance industry? Who knows.

Distillery oil, removed in litre quantities from the side of the still was shown to contain these compounds and can be considered as a concentrate of the higher boiling point flavour compounds of rum.

 

Fractional distillation of distillery oil produced « fusel oil » containing the higher alcohols (n-propanol, isobutanol, isoamyl alcohol and active amyl alcohol, BP to 132°C) and a residue termed « rum » oil containing compounds with a higher boiling point than isoamyl alcohol.  Only the analysis of the « rum » oil will be discussed.

Allen uses both a Lecky and Ewell still and a Bower and Cooke still to purify the fractions for analysis. He has citations for each still and it may be helpful to dig them up to see what they were like. A lot of this equipment is still very useful.

He has got an entire liter of rum oil and does not say how it smells. There are a lot of esters in the oil and they get hydrolyzed with sodium hydroxide to concentrate the remaining compounds. The hydrolysate gets fractionally distilled and the fractions analysed. Part of hydrolysate is alcohols that were liberated from the esters by the sodium hydroxide. Due to how the sample was separated from fusel oil, some compounds like acetals reported in rum oil by others may not have survived.

Allen goes on to perform continuous liquid-liquid extraction on multiple liter batches of raw rum. Its seems like he does five batches and winds up with 5 liters of pentane to distill from. The non volatile product is an oil and the volatile product is split into two fractions. The ethanol was in the first fraction and the second fraction was an oil-water azeotropic mixture. The oil was separated, dried with anhydrous calcium chloride and added to the water-free residue in the pot. It would be nice to know how they smell before he blended them together!

This oil gets redistilled in the same apparatus and separated into two fractions collected up to 132°C so everything is well over the boiling point of water. What isn’t clear is if pentane is used in this distillation. These days this distillation would be done under vacuum and a teflon coated spinning band distillation column would be used because holdup, or the clinging of liquid to the glass apparatus, starts to become significant. Descriptions of what is explicitly happening by now have become a little disjointed and I’m having trouble following the transitions.

This oil was redistilled in the same apparatus and separated into two fractions. The larger fraction, collected up to 132°C, contained the higher alcohols to isoamyl alcohol and was called fusel oil. The residue (100 mL) in the pot contained compounds with higher boiling point than 132°C and was called « rum » oil. After four more such distillations, the combined residue amounted to 500 mL.

If any of this smelled really good, wouldn’t he be likely to mention it? Wouldn’t he be likely to show it to a distiller and get some gears turning? Wouldn’t Bundaberg rum be less likely to be so lame?

In the next step, the specialized stills get some use which apparently feature vacuum and a series of 10mL sample were collected until the temperature hit a certain point. The pressure was dropped and more 10mL samples collected. This multi stage pressure drop to avoid decomposition may have been because the equipment was a little more primitive than what we commonly use today. All of the collected fractions see some spectroscopy to identify what they are.

The rum oil goes through some more hydrolysis with more sodium hydroxide with the products extracted into more pentane.

The paper seems to get cut short after Allen identifies 1,1,6-trimethyl-1,2-dihydronaphthalene. Allen does not use the modern abbreviation of TDN, but this is a congener that is infamous in aged Reislings and is responsible for the petrol character which at the right levels is often prized. Allen drops a little bit of history on this compound but does not mention wine at all. I linked to this paper on TDN in the beginning, but here it is again if anyone wants a primer.

The entire work seems to be the basis of a masters thesis to which the next paper I’ve requested may add to.

I really don’t know what to make of the TDN discovery. Allen does torture his sample and we should remember that in continuous column distillates, this fraction is mostly discarded. Google searches for 1,1,6-trimethyl-1,2-dihydronaphthalene +rum yield nothing.

But, when you read the AWRI paper, TDN is noted as related to carotenoids and extra smart blog reader Matt Power brought them up recently (Matt actually inspired the tracking down of this paper after mentioning 1,1,6-trimethyl-1,2-dihydronaphthalene, but I did not immediately connect the dots):

Are components of rum oils microbiologically derived in these manners, rather than from the canes themselves? Carotenoid bio-decomposition is known to lead to a spectacular array of interesting chemicals

This comment come from the Arroyo’s Oidium post about ethyl tiglate and relates to my hypothesis that the peculiar character of rum oil comes from the splitting of glycosides by the enzymatic action of alt yeasts like Schizosacharomyces Pombe. Rum oil may be more complex and the product of more mechanisms.

Outlining the mechanisms may even unlock the potential for finding more terroir in rum from molasses. A rum can only tell us a story of a place if we learn to read it.

[It may be possible to take a modern GC-MS look at a heavy rum and try to categorize all the low volatility congeners found. This may give us a distribution of what channels they come from.]

Whiskey Verdigris

A search for something to help a blog reader prompted me to take a trip back through the databases. More and more literature is digitized every year or has its copyright expired.

This paper on Whiskey Verdigris was a fun one for me because I love looks at distillation phenomena that are seldom explored. If you encountered a still puking verdigris as a first time distiller it may be a ‘wtf?, that’s not in the text books!’, but it is a phenomenon understood to be normal by experienced commercial scale distillers. My very first explanation of the phenomenon was back in 2014, A Still Operation Phenomenon Explained.

The paper is from 1937 and the experiments were conducted down in Kentucky from a sample of whiskey verdigris secured for the authors by a former University of Kentucky alum. This is all pre chromatography era so they explore and torture their sample MacGyver style to elucidate what the hell it is and how the hell it got there.

Copper is reactive and distillation is all about concentration so waves of reactive compounds move through the still. The end of a spirits run also has a unique relationship with the beginning of the next as we learned in Demisting and the Spirits Safe. Stuff at the end of the run, distilling primarily with water vapor (but not necessarily water soluble), has a tendency to be sticky. This stuff often gets stuck in the condenser, affixing to the copper, but is liberated by the next run where it is soluble in the very high alcohol content of the heads fraction. Chemical reactions happen with the copper producing a colored patina that takes the name whiskey verdigris though it is chemically different from the classic verdigris of the decorative arts (but no less beautiful!). Another strange phenomenon can also come along depending on how a distillery preps its beer (they usually try to avoid this). If the beer has not been de-gassed and liberated of its CO2, as it heats, it will have a tendency to belch. The liberated CO2 has both a corrosive action and a force that can scour the inside of the still and puke out whiskey verdigris. If you have this going on you may want to figure out how to de-gas your beer because the raw copper revealed can negatively impact your flavor.

The short paper is worth a read. These chemists were brilliant and it is fun to try and keep up with an understanding of what the hell they are doing. Among the many parts of their experiment, they are making whiskey soap and getting to smell isolated fractions that few of us will ever get to experience. Wonderful stuff.

If you have some, either send in a photo or mail me a canning jar of the stuff. I will turn it into paint and create a neo-pointalist self portrait.

As the concentration of alcohol falls in the doubler a white, insoluble, fatlike material appears in the trial box. Although most of this goes back into the singling tank, some collects in the condenser and is partially dissolved and washed out by the higher alcoholic content of the next distillation. This appears in the heads or foreshots of the next distillation and is colored a distinct green. This part of the insoluble material goes directly into the whisky well and dissolves in the strong alcohol present. Thus a part of the original volatile fatty material collects in the singling tank, and part finds its way into the whisky. The trade calls this material “verdigris” which is an unfortunate name since it has no connection with the verdigris of commerce.

 

The amount of this material is small in comparison to the volume of alcohol produced. Probably 250 grams per 30,000 liters of high wines would be a fair approximation, although no exact figures are available and would be very difficult to obtain.

 

UNSAPONIFIABLE MATTER. The ether extracts of the soap solutions upon evaporation yielded 1.4 grams of a viscous oil having somewhat the odor of corn.

 

The green solid when leached with hot alcohol was dissolved, leaving a brown solid. Upon filtering and cooling, the alcohol solution deposited green crystals; hence the palmitic acid is considered to be held as a cupric salt.

 

The higher fatty acids and their derivatives found in whisky verdigris without doubt originate mainly in the corn (3) which makes up from 60 to 89 per cent of the total grain used in making Bourbon whisky from which the sample was obtained. The corn oil alone does not offer an explanation of the presence of laurate and caprate esters, although Hilger (6) reported the free acids to be present in fusel oil. The occurrence of the various fatty acids and their derivatives in the beer is easily understood, but their presence in the distillate is more difficult to explain. Although it is known that the higher fatty acids are volatile in steam, or at least volatile in steam containing the vapors of more volatile acids, it must be remembered that this is not purely a steam distillation.

 

It is possible that the acids distill and cling to the copper condenser, and that partial salt formation (11) and esterification take place there. The majority of the esters are probably formed in the beer, and many other possibilities are obvious although none appears to explain satisfactorily the absence of stearic acid or its derivatives. Although this acid has been reported in fusel oil (6), the writers were unable to find any indication of its presence in whisky verdigris.

 

Whisky verdigris has a strong odor of green whisky and may be said to be yeasty: although none of the substances mentioned by Hochwalt and others (7) were found, their hydrogenation process may owe part of its effectiveness to the reduction of the unsaturated derivatives which otherwise become rancid.

These two photos come from rum distiller James Copeland christening a new still.

An accumulation of beautiful whiskey verdigris.

Insoluble flecks collected in a low wines receiver.

Whiskey verdigris can even end up as a precipitate in the tales fraction.

Insoluble flecks can be collected in cheese cloth suspected over the low wines receiver.

The last four photos were courtesy the wonderful Kings County Distillery which primarily produces a bourbon.

This last photo is from the Auchentoshan distillery in Scotland. Courtesy an astute reader with an eye that doesn’t miss much.

Feel free to write in and add to the photos. They can be attributed or submitted anonymously with the type of spirit distilled.

The Evaporation of Wealth

John Ralston Saul, in his 2005 Collapse of Globalism, keeps mentioning the evaporation of wealth. The concept is curious, elusive, and basically not talked about by anyone else because it challenges a lot of ideas in economics. We have to remember that money is not real and something that always sits a top the value of an asset is the concept of utility (which is hard to measure so economists hate it). We all know economics eventually have to go beyond a focus on GDP and switch to harder to quantify measures like happiness, but that is barely discussed. As JRS likes to remind us, if you ask around at economics schools if they’ve changed their curriculum since 2008, they will admit not by much.

There is a growing anxiety related to the not yet widely understood evaporation of wealth phenomena that is driving the democratic socialist movement which many elites like to ridicule. Our leadership and even our intellectuals are really weak on economics so they tend to grasp for or mock ideas like socialism. They cannot seem to see giant problems staring them in the face.

The easiest way to begin wrapping your head around the evaporation of wealth (exacerbated by globalism) is to consider decades ago what happened when women were added to the work force. If a family has two incomes, it should be wealthier, but that just hasn’t been the case. We once had a prosperous country where a family could support itself and achieve considerable happiness on a single income often working only 40 hours a week. Somehow we have evaporated that entire extra income as well as a hundred years of other accumulated assets. A lot of this has to do with how we allocate the tax burden and how we allow sanctioned corruption in the political process (lobbying).

A lot of people think of the evaporation of wealth only as inflation and deflation as well as speculation, but there is a lot more subtlety to it. Evaporation may also not be the best metaphor, but it is a good starting point. Evaporation also happens by degrees and is not an on or off phenomenon. Not all saving is evaporative, but some is significantly as the piles grow and the amounts in the billions lose productivity. When middle class people benefit from tax cuts and can save, their savings have normal utility, but when the 1% and .01% get a tax cut, the money has significantly different utility and is essentially evaporated or put into permanent storage where is does not contribute to the prosperity of the country. At the moment there is only one Elon Musk, but more on him later.

The main focus of this blog is the collecting and republishing of old beverage technology research papers and they are a great example of evaporation (my library card is my condenser!). These papers were publicly funded research that took place over large spans of the 20th century and they should be part of accumulated American wealth and resources with utility to draw from, but somehow they managed to become hidden.

This is just like money we stashed and forgot where we put it, but it also gets wrapped up in various infamous pay walls that privately tax you when you try to access your public wealth. We do not understand our miscellaneous public assets. We improperly archive them by under funding our libraries, allowing private gatekeepers that should not be there, and essentially evaporating vast utility. Americans have so thoroughly forgotten their public resources that they’ve allowed lobbyists to hijack our copyright system, robbing the public of wealth that is supposed to accumulate.

The new American distilling scene is approaching a billion dollars in market value and for some reason this rickety blog is the largest source of advanced educational material because I condensed a forgotten trove of public research returning our wealth. I’m currently holding multiple pieces of forgotten public research I haven’t shared that will dramatically advance every major distilled spirits category (I just leaked the most major piece to a spirits writer you all adore).

The biggest art museums which are quasi public-private (but essentially have public missions) are quick to tout statistics like only 3% of their collection is on view at any one time. This means they evaporated nearly 97% of a few millennia of art they rounded up and put in warehouses. Civilization should have accumulated so much fine art by now that it is coming out of our ears, but we put it in storage where it has near no utility. This art could adorn our public schools which look like prisons and countless other public spaces like post offices and public libraries. If the West is turning its back on Enlightenment values, spread that damn Enlightenment art!

Vladamir Putin is thought by many to be the richest man in the world, but all the wealth he robbed from the people of Russia has very little utility. It is all hidden and sheltered because he is not supposed to have it. Russia has vast natural resources and it has been extracting them for decades during their recent kleptocratic era, but all that wealth basically evaporates because they have no Elon Musk who can create new prosperity from so much accumulation. Kleptocratic wealth is not original prosperity, but merely a transfer from the public good. Much of it goes to countless 40 million dollar Manhattan apartments that no one lives in. Though many of these investments have a dollar value, they have no typical utility.

We drag along far more military these days than our grandfathers did who supported large families working one blue collar job which is a wide avenue of wealth evaporation. The world may have changed, but it takes us so much more military to get the same utility (hell, we may get less because we are in perpetual conflict). At forty hours, we used to drag along diplomacy and the draft, but now we drag along bloated pork project fighter jets and multi million dollar missiles that are useless (declining utility) against the increasing irregular warfare phenomenon.

Spending on police or the TSA is relatively less evaporative because it is labor intensive and employs the middle class, but that is starting to change as the police militarize and use expensive swat teams to serve simple warrants. We are also evaporating money into settlements for police misconduct that we likely aren’t even legally allowed to track and study. The expense of wrongful death after wrongful is a part of that albatross around the neck of every citizen keeping them from supporting a household on 40 hours a week.

Much global tension comes from the rapidly deflating value of fossil fuel assets. All parties know their fossil fuel wealth is slipping into relative uselessness and there is a race to unlock this wealth before it evaporates. As a non-OPEC member, the U.S. is currently winning big time and as demand slows, the U.S. keeps opening its faucet to keep the price down though many parties have innovated and automated to the point they can make money on $35 crude.

In the new era of fossil fuel divestment, there is actually multi tiered evaporation going on. First, oil wealth is evaporating like just housing wealth in a deflating real estate bubble. Then secondly, this wealth is distributed to where it’s utility is low so it does not create a diverse economy that can help the civilization it serves move on. Petrol-states rely on a template of transference prosperity, they have proven unable to create hard won original prosperity.

Many futurists are starting to discuss the parasitic city where housing crisis are developing. Housing speculation is transference prosperity and those that benefit from it fall into the petrol-state template and can likely never create original prosperity. Money is sucked up from would-be middle class innovators and perpetually put into storage. Vast wealth is sucked up by the land lords to create pretty mundane lives of no particularly amazing happiness (I know countless of these people personally via my restaurant). Ostentatious behavior would condense the wealth and we don’t even see that. The only place the money ever goes is to corrupting our political system.

Commodity speculation is a classic hated layer of evaporation. Imagine the supply and demand curve of the price of oil. Now add another elusive pulsating curve atop it and the space between is the meddling of the spectators. When you reach in, you cannot grab that efficient price, you can only grab something from that layer above belonging to spectators and pay their private tax. Speculation is a transference of wealth from those trying to create original prosperity with the commodity to the speculator who is often Goldman Sachs, Exxon, or actually myself.

I have had great success as a commodity speculator and have funded a lot of my art projects that way. The wealth I transfer (should be illegal) is not evaporated because I use it at normal utility. Putting the money to use, I am overall a prosperity originator. The first dollars Goldman Sachs makes are not exactly evaporative because staff eats, clothes themselves, drives to work, and participates in gross ostentatious behavior supporting original prosperity. The last dollars, the majority, are supremely evaporative.

Oil is a strange ethical case. If the price is high we will use less creating less environmental burden and alternatives may seem more viable. If the price is low, oil isn’t always worth taking out of the ground. Oil companies make significant money on speculation and at the moment it keeps the price up in a viable zone. Banning speculation by financial regulation is a choice we are allowed to make and could eventually propel oil out of it’s viable zone downward toward staying in the ground. This is complicated by the fact that a lot of speculation these days is betting against oil. It starts to melt your brain and I would rather make my money via my workshop.

I work in an odd neighborhood restaurant in a super zip where I’ve noticed hundreds of millions in pretty evenly distributed wealth sitting around on a Sunday night. The modesty is amazing and there are bank executives with Timex watches that drink $9 Montepulciano by the glass. Everybody knows our names and there is no hint of any gross culture associated with Wall Street (so I’ve set the scene with all the “elites” you hear about #banalityoffinancialevil). Second only to 45, everyone talks about Elon Musk. These bankers, real estate tycoons, heirs to fortunes and family businesses are all enamored with Musk’s massive scale original prosperity and intuit that his wealth draws from a more noble category than theirs (but sadly they leave it at that). Their money is in storage because they don’t know what to do with it besides protect it from taxation while Musk is commanding hundreds of billions and knows what to do with every dollar like someone on minimum wage.

Musk is what we thought trickle down economics was for. Reagan might have had the best intentions, but the country could not produce enough prosperity originators for all the evaporators. Those that didn’t spend their capital actually inventing stuff, the evaporators, they had plenty of money to influence government and here we are today.

There turned out to be no trickle down economics, but there certainly is the evaporation wealth.

 

If you are intrigued, I took a break from beverage technology blog work to write:
Optimism is your weapon!, Inherently Good, and the Public Good
What is water? Swimming in the Public Good
Our Social Contract, Taxes and Charity
Ideology and the Supernormal Stimuli
A New Institution of the Public Good: Mandatory Civil Service

You can check out my Victorian door hardware workshop on IG: @houghstfoundry

Arroyo’s Oidium

In Arroyo’s 1945 Studies on Rum, he presents two different paths for symbiotic fermentations to produce full bodied rums. The first path uses a bacteria while the second path claims to use an Oidium (a mould), but recent research shows it may actually turn out to be a type of alt yeast.

Where did he get the idea anyhow? Arroyo has pretty much no bibliography other than the classic rum texts, but appears to cast a wide net and is well versed in emerging ideas in bio technology. He mentions finding this “mould” on the sap of a tree in a shade grown coffee plantation (shade grown coffee is really interesting). He does not say exactly what specific tree so it is hard to pin down because shade grown coffee plantations are known for spectacular diversity.

Besides, a mould of the Imperfecti group, Oidium Suaveolens, was also found very well adapted for the production of a special type of heavy rum.

Pages later he tell us more:

Another special type of heavy rum was produced during our studies and experiments. This time the raw material used was sugar cane juice. The yeast strain used was No. 764 and the auxiliary ferment was a member of the Fungi Imperfecti, Oidium Suaveolens. The Oidium was found and isolated by the writer from the sap of a tree much used in Puerto Rico for shading coffee plantations.

A study of this Oidium revealed that it would grow very fast in cane sugar juice media with the production of a thick film over the surface of the liquid. It was further discovered that it hardly touched the sugars in the medium, but that it was a good producer of esters and organic acids from the proteins of the raw material. A fragrant odour, very similar to that of ripe apples was the predominant aroma observed.

This Oidium was used as an auxiliary ferment for the production of heavy rums from sugar cane juice in two different ways: (a) a sterilized sugar cane juice mash of from 12.0 to 15.0 per cent total sugars was inoculated firstly with the Oidium culture. After the Oidium film was formed on the surface of the medium it was allowed to act up it for a period that could vary between 24 and 72 hours or more if desired. Then the mash was inoculated with an active footing of yeast No. 764, and the fermentation was carried to completion. (b) In the second method the yeast was allowed to operate alone in the substrate, and towards the finishing of the alcoholic fermentation the Oidium culture was inoculated. The Oidium fermentation was allowed to act then for variable number of hours, as desired.

Both methods worked satisfactorily in the creation of a new variety of heavy rum out of sugar cane juice mashes; but the rums obtained differed somewhat in each case, those produced by method (a) being of intenser taste and higher aromatic tone.

Many databases exist like the Global Biodiversity Information Facility that have listings for the organism, but they contain no spelled out history of discovery that may elude to where Arroyo got the idea (A Russian database points us to Geotrichum Frangrans which can be purchased here from the American Type Culture Collection ATCC). Arroyo did name the organism correctly as Suaveolens, and calling it an Oidium may point to the Russian biologist Krzemecki who possibly discovered it in 1913 based on language included in the GBIF entry. Arroyo may have also been hip to the organism by reading the mycologist Christine Marie Berkhout. Or maybe Arroyo never read her 1923 doctoral thesis that (quoting wikipedia) was later described as marking “the beginning of the rational systematics of the anascosporogenous yeasts” (I’m way out of my depth, but trying to bridge the gap between Arroyo’s mould and the recent researcher’s recategorization as yeast. The difference between a mold and a yeast is that molds grow with multi celled hyphae while yeast’s are single celled).

We are building up to some links to great modern research papers, but we should pause for a moment. The whole point of this exercise is to (a) celebrate how fucking cool Arroyo was, (b) help modern rum writers who may talk to producers and find evidence of these techniques used in a production, (c) help new producers jump off on this, and lastly (d) celebrate the contemporary researchers who will help us bring more of Arroyo back to life and create new exciting styles of rum.

Contemporary research on this organism and my realization that Arroyo may have been incorrect about it being an Oidium are lead by Thomas Petit and Eric Grondin working on the island of Reunion off the coast of Madagascar.

This brief info graphic style paper by Petit mentions participation in a European COST (cooperation in science & technology) bioflavour project. After scouting yeasts, Suaveolens, came up as their most significant flavor producer, specifically producing the valuable ester, ethyl tiglate (a known semio-chemical #pheramone).

To back track a bit, from an old text that summarizes abstracts, we can glean a little bit of the interest from 1923.

A study of Ester-Forming Yeasts.
Ulrich Weber, Biochem. Ztshr., Berlin 129:208, April 19, 1922.
Experiments are described that sought to determine the conditions under which the formation of fragrant esters takes place in some lower fungi. The question was dealt with by physiologic experimental methods. There were employed Willia saturnus Klöcker, Oïdium suaveolens Krzemecki and Siachsia suaveolens Linder. These organisms were raised in pure cultures in nutrient glycerin and mannite solutions under different conditions.

Results showed: In the observed yeasts and imperfecti fungi the ester odor typical for normal cases is not developed under all conditions. Cases occur in which, in spite of the most abundant development, no ester formation takes place, as in the case of growth in a carbon dioxide atmosphere. Esters are formed only when the simultaneous fermentation of carbohydrates assumes the role of sugar fermentation and liberates the energy requisite for the decomposition of albumin. Addition of alcohol enables a qualitative alteration of the ester odor to be attained. The employment of different nitrogenous nutrient media achieves an alteration of the odor only when other amino-acids are thereby presented simultaneously. Following addition of leucin a distinct odor of amylester is perceived. The ester odor of the species here investigated, which is always observable under normal conditions, is therefore capable of being influenced experimentally both qualitatively and quantitatively, as it is possible to alter both the character of the odor and also to prevent its occurrence in spite of the best development of the fungus.

The Yeast, A Taxonomic Study has some useful information on understanding what exactly the Saprochaete of Saprochaete Suaveolens entails.

Swedish Wikipedia provides a great bibliography.

And finally we come to a few spectacular modern research papers: