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We are seeking out the most extraordinary aromas in rum production (not esters) which are typically bound as glycosides and need to be unlocked. Unlocking this special aroma is tricky; you may follow all best practices and come up dry. A big question is where are the precursors and in what relative proportions? Arroyo found all that he wanted in molasses at high pH with a fission yeast, but he may have only been successful with very specific molasses while others molasses has very little chemical potential. Another source of precursors may be cane trash and new research is starting to look at the skin of the cane. Jamaica is known for using trash cisterns in heavy rum production but the significance has attracted little attention. I finally give it some preliminary thoughts while I devise research scale methods for exploring the potential.
Examining cane trash has long been on my agenda. In some traditions, it participates in cultivating yeast (& bacteria) at the start of fermentation while it is also used an the end for the production of flavour (thus sandwiching alcoholic fermentation). There are a lot of ways to skin the cat with heavy rum and many ingredients will have dual roles so objectives are something we need to look at. It may also help to collect as many references as we can. Trash usage has been imprecisely implicated with contributing rose ketones like damascenone to ferments and a new generation of research is starting to examine the skin of cane as a source of high value precursors, but funny enough, outside the heavy rum tradition. Basically, there is aroma in the skin of the cane as well as other specific parts of it’s anatomy like the tops, but much of this is bound aroma that needs to be unlocked during fermentation under narrow conditions. Liberation of bound aroma may represent the heights of terroir and/or varietal character in a rum.
If cane trash is used in heavy rum production’s equivalent of a yeast mash, emphasizing healthy growth and aroma development as an objective, what mechanisms are in play and how can things be optimized? Are fission yeasts the only active organism or would cellulosic organisms play a role? What actors need what in terms of temperature, pH and nitrogen to do their work?
The same questions can be asked when cane trash is used as an additive for flavour or acid or muck during a resting phase before distillation. Different actors may enter the scene and they may have different needs for their own growth and that of releasing bound aroma. A 2002 thesis sponsored by the Savannah distillery in Reunion, maker of the rum industry’s newest grand arôme rum, examined aroma bound as glycosides in a variety of molasses and found incredible diversity. Cane and its byproducts are full of potential that is typically flushed down the drain or composted.
The likely actors:
Native cullulosic yeast consortium.
Fission yeast (brought possibly by fruit flies).
Mildew yeast (brought possibly by fruit peels).
Native LAB (with some forms beneficial while others are certainly detrimental).
Acetobacter (likely produces conditions that favor dominance of specific organisms).
Butyric acid bacteria (traditionally brought from soil or even manure, whereas Arroyo isolated the unique saccharobutyricum from a particular substrate during a World’s Fair project).
Brettanomyces (may release far different bound aroma than others which may be inferior stuff like TDN/TNN).
*”Pineapple disease” mold (not well studied and it is not known whether the mold produces its characteristic aroma or releases it from the cane. Not all cane varietals produce aroma).
[Pineapple disease needs more attention. Some of the claims of getting high value aroma from trash cisterns used at the beginning of fermentation may have come from pineapple disease. The disease occurs on both cane and pineapple so some instances of luscious fruits being added to cane trash cisterns may have been attempts to introduce aroma producing black mold to tanks of cane. There are few instances of this being described besides the wring of molasses technologist Hubert Von Olbrich. There is a lot of conjecture here because if it were so simple, you think you’d have a continuous lineage of it being practiced.]
It is not public knowledge if cane trash as a substrate is known to the industry as a source of aroma precursors or if it is only thought of as a scaffolding such as wood chips or cork in a classic vinegar generator. Most 19th century distillers thought trash was simply free—off the books sugar that would become free acids that contributed to the higher than average value of Jamaica rum. It is not known publicly whether cane trash is rotated in and out of cisterns on any regular basis or if it takes significant time into the season to produce any aroma due to build up of certain actors. It is known that liquid may move between multiple cisterns. No literature ever discusses pH of the various cisterns, but it is well known lime is added at various times. It is not known whether trash is ever from exhausted pressings or only from canes rejected by the mill due to sanitary concerns (damage can create a loss of sucrose making the cane not viable to process). It is not publicly known if there are any unique opinions on how trash is processed across distilleries that still use it (Do any long lost marks get a trash filled flavour cistern started with the manure of a pig fed only jerk chicken and Guiness Foreign Extra?).
[Some of what I’ve seen so far is that well acidified trash in water quickly grows an epiphytic film yeast and produces an aroma that is kind of like cooked corn. I’m not sure what exactly is in the broth but it has given me spectacular results as part of my fission yeast growth media. My guess is that the aroma relates to protein breakdown which can become a nutrient for the yeast that when metabolized often produces aroma. This parallels the breakdown of protein in grains for a yeast mash. If the cistern is left to become stagnant, the film can become so thick it allows molds growth atop it.
I’m betting the trash can be thought of as worn out when all or most of its nitrogen is given up into the broth. When you drawn down the broth and replace it with water, you’ll eventually have nothing to extract. You could probably quickly generate some numbers.]
Old abstracts summarizing the works of Allan in 1905 mentions this:
“Acid” is made by fermenting “rum can juice” which has been warmed in the coppers. To this juice “dunder” is added, and sometimes a little “skimmings.” When fermentation is nearly over, the fermented liquor is pumped on to “cane trash”, and allowed to get sour; the ripe “acid” has an odour like sour beer. Sludge settled out from fermented wash is added from time to time.
“Flavour” is prepared by running fermented cane juice into cisterns outside the fermentation house along with cane trash and “dunder” which as been stored from the previous crop. The fermentation of the “flavour” in presence of cane trash with the addition of “dunder” is effected three times before the “flavour” is ready.
“Skimmings” are run from the boiling house into cisterns half full of cane trash, and are allowed to ripen for four to six days before they are used for setting up the wash.
We see three distinct uses of trash.
[I setup a three stage flavour cistern with cane trash and it actually attracted vinegar eel nematodes (they are benign and frequently found in vinegar productions). The nematodes need oxygen and can only live above the surface feeding on cellulose from bio films like vinegar mothers that grow atop the liquid. I should probably be feeding this frequently, adjusting up the pH, and even throwing away what I draw off if I have no place for it just to see it come to any kind of equilibrium. These cistern can also grow mold which is probably not desirable if they become too stagnant.]
Selections from the old literature that follow may not be too helpful because all the descriptions come before awareness of pH which is often critical to understanding enzymatic processes. They also come before any particular awareness of yeast type, such as fission yeast. Cellulosic yeast in the context of aroma are still barely understood. When it is repeatedly said that some achieve the desired aroma without effort while others try hard without success in finding a pattern, what can our foundation of basic science contribute today?
I eventually got exhausted from hunting references and never even got to the Experiment Station Works of Allan, Ashby, and Cousins. You may always consult All The First Person Accounts of Jamaica Rum Production Made Accessible if you want more descriptions of trash use.
I am not linking to any modern work because those papers and their translations were the thoughtful gifts of investigators presently trying to make progress on understanding the potential of this topic.
A newly translated work from Saussine, 1899, tells us something juicy right away:
Near the sugar refinery there is a pit, trash cistern, or dirty cistern, filled with bagasse where the scum from defecation and residues from filter presses are collected. Fruit peelings are sometimes added. Various ferments which live on the cane or on the fruits develop abundantly on such a nutrient medium: alkalines quickly neutralized the products of fermentation that soon develop a frankly acid reaction. It is a very energetic yeast but very variable in its composition. Experience has taught manufacturers that the use of this yeast in fermentation tanks favors production in the alcohol of an oily substance to which they attach great importance.
Residue from filter presses is the evolution of skimmings. Sometimes these press muds are called cachaza and they are attributed super natural powers as a fertilizer beyond their nitrogen content. Cachaza may support healthy yeast growth but also be the building blocks of vesouté related esters. We now know Hampden flirts with Jack fruit, but they do not seem to be used in a trash cistern. Other very old sources mention “luscious fruits”, which does not sound like a Jack fruit, but there are no detailed references to what fruit contributes. With Jack fruit, it could merely be vitamin B while other fruits could contribute aroma beneficial mildew yeasts. “Alcohol of an oily substances” tell us nothing we can draw from.
Thomas Roughly, writing in 1823, gives us among the earliest ideas of trash use in fermentation:
The fermenting cisterns should be well cleaned and dryed out then filled with some green mill trash, which has not been much squeezed, that the fermentation arising from it may sweat and warm the cisterns. This trash should remain in them covered up till they are wanted to be filled with liquor from the mixing cistern.
What happened next? Were they putting wash atop the sweated trash?
In 1844, Wray, reiterates something similar:
At the beginning of crop, (should no old dunder be on hand from last year,) the cisterns are cold, and what is termed, out of season, and consequently take sometime in settling a fermentation, for which reason, it is a common practice to put a quantity of cane trash into the empty cistern and set it on fire, whereby the cistern is slightly heated, whilst others put hot-water in, to induce a more early fermentation.†
(† The host skimmings are a great assistance in heating them, but sometimes filling the cisterns with green trash from the mill yard is a good plan, as it speedily begins to sweet [sweat?] and steam, warming the cisterns thoroughly, they are then very slightly limed, and filled with wash.)
When you consider a cold cistern, one beautiful idea I learned from Cory Widmayer is that cellulosic bacteria are favored by the cold and make grow to relative dominance. Their activity may also release bound aroma in the cane.
Wray then tells us about the rind of the cane:
From the resinous aromatic gum, resident in the rind of the cane*, the well known flavour of rum is generally understood to proceed: but this is very different when a spirit is manufactured from molasses alone, for then although no trace can be discovered of this distinguishing aroma, yet a very plentiful impregnation of an empyreumatic oil is disagreeably perceptible. This is accounted for by the pernicious transformation effected on the resinous gum contained by the intense heat of the boilers, during its passage through them. In the skimmings this action has been but exceedingly partial in consequence of the comparatively very slight degree of heat it has been subject to.
(* Volatile oil contained in plants is changed into resin by the absorption of oxygen. See Leibig.)
We observe Wray claiming the flavour of rum is derived from the rind of the cane and a cryptic explanation of why you cannot make true rum from molasses alone (add it to the pile!). Some of the empyreumatic aroma may be a thing of the past due to the adoption of vacuum pans to reduce process temperatures.
Wray then gives his famous pineapple rum anecdote; referencing Liebig again, of course:
Besides this essential oil of the cane, we have reason to believe, that a further accession is gained during the process of fermentation, from small pieces of the cellular tissue in the wash generating an essential oil as its decomposition takes place*. I have myself no doubt that such is the case, and a few simple reasons for my belief may suffice; for instance, in making rum with a very rich perfume of pine-apple, it is only necessary that we put the bare rind of the fruit into the fermenting cistern, and let it remain there until the process is completed: this is only that the rind in which the essential oil resides, shall as it decomposes impart to the wash its peculiar flavour, which it then does, abundantly and freely. This fermented wash, so impregnated, yields on distillation what is generally called “Pineapple rum.”
Was the fruit peel referenced by Saussine pineapple? We still cannot say and Wray’s unique methods for pineapple rum were not well referenced later.
Wray starts explaining his experience with peach leaves and finishes with the idea that all rum ferments should feature pieces of whole cane—cellular tissue a la trash:
Peach rum again, is made by placing the skins and kernels of the fruit, with the blossoms, into the fermenting wash, by which the essential oil is separated and becomes incorporated with the wash, by which its characteristic perfume is secured to the distilled spirit. Indeed this change of flavour may always be influenced at pleasure, and a good distiller knows well how to improve his crop in this manner, so as to command a very superior rate in the market, without having recourse to the various deleterious compounds which are used by less able, but more dishonest operators. In making use of the essential oil of foreign auxiliaries, it should be borne in mind, that the flavour is very fleeting, and in no way to be relied on, whereas that obtained from its own plant, the cane, is its natural aroma, and not so readily volatilized; therefore it is in my opinion, a good plan to have a small quantity of the cellular tissue of the cane thrown into each cistern set up.
None of this advice about including cane trash or tissue makes it into Wray’s next, more famous, 1848 text.
We get one more note from Wray that is hard to interpret:
In some canes this resinous gum (and essential oil generated on fermentation) more particularly abounds, and has a very pernicious effect on the sugar and rum made therefrom the latter in such case must be peculiarly treated as I will show in its place.
I think what Wray refers to here is the original idea of hogo where bound, but aroma-negative character is released like TDN or TNN. This may be related to the varietal character of certain canes and Wray had experience from all over the globe.
The great Agricola, W.F. Whitehouse gives us the briefest note that trash of the mid 19th century were derived from the infamous rat eaten rum canes:
Note.—Where rum-canes are ground for the purpose of accumulating trash, the still must be run with wood; but, if the process were carried on on a large scale, the trash would have to be used for fuel under the still.
Does rum cane make better trash?
We leap forward a bit, to 1871, and J.S. gives us an interesting description of trash use at the beginning stages of fermentation:
Leaving the sugar to drain, let us return to the millhouse to collect materials for the distillery. Mill-bed trash, sour, or rat-spoiled cane, suckers, &c., are all collected and ground for the purpose of making rum. Then from the boiling-house is taken the trash and lees from syphons, and skimmings from the coppers. All these meet and mingle in a large receiver, or mixing vat, which is continually ebbing and refilling, and kept fermenting. From this a certain quantity is put in the bottom of each vat or cistern to be set up, generally about 250 gallons to a vat of 1000, which with 475 gallons Dunder, 200 gallons of water, and 75 gallons molasses, will make up a vat of liquor standing thus by Long’s saccharometer (which shows degrees of specific gravity above water, and about 7½ to 1 of Baumé’s scale):
This is a description of an old, Liebig-style, spontaneous, yeast starter and it features plenty of trash. Was it there because Wray and others had suggested it a generation ago? Was it just a little bit of free sugar/nitrogen or was there very obvious aroma value?
J.S. gives us a quick reference to luscious fruit:
Among other efforts to impart a flavour may be noticed that of adding certain odorous ingredients to the wash previous to distillation, or luscious fruits during fermentation.
Was that fruit tossed into a trash cistern or not?
When Patrick Neilson comes along, dirty cisterns have already been in use, but the were used differently. Neilson describes this material as being removed from productive use. You typically distilled the dirty cistern separately. It was a revelation of aroma that had Nielson thinking differently:
What in fact first drew my attention to seeking out a flavour in rum was the running I first got from what is known here as the dirty cistern, a receptacle for all the refuse, bottoms, &c. of the other vats; I was astonished to find at the can pit mouth, as the rum came over, an exquisite flavour. I considered and said, why not make all the other vats, dirty cisterns, or at least to some extent, and I proceeded accordingly, with very happy results. I may state that the said dirty cistern besides being a receptacle for all refuse, is allowed to go on fermenting away, sometimes dead, sometimes alive, for three to four weeks; in fact, a sort of putrefaction goes on, and an acidity is produced which frees the aroma, hence the fine flavour when full.
So a dirty cistern should smell good when full?
Patrick Neilson goes on to describe a pivotal moment for rum but there is no apparent use of cane trash. Did they see a renaissance as skimmings availability waned?
R. H. Burton, in 1975, gives us an incredible telling of rum and even opines on the Old Jamaica, but there is no mention of cane trash:
Planters who wish to make good rum crops should be careful to collect all the sour canes from the cane fields; the suckers and plants,—in fact, no portion of the cane unfit for sugar should be lost.
I wonder if there was this eventual tension between sugar factories that did not want to touch this trash and distillers with a rememberance of Old Jamaica who did not want to give up on the value of rum canes, but had nothing but cisterns to use it.
On most estates a mud-vat is kept; this is frequently placed in the can-room, or some out-of-the-way corner. There are many opinions on the utility of a mud-vat; all, however, agree that the best flavoured rum is produced from it.
There was simple economics to the Jamaican impulse to explore every aspect of sugar cane offal:
It must, however, be conceded that on an estate there always must be a great deal of refuse that can only be turned to advantage by distillation; rat eaten and wind broken canes, suckers, tops, and bruised canes, all unfit for sugar, will, if constantly and carefully collected, make a great deal of very fine flavoured rum; washings of tanks and apparatus, the coarser part of the skimmings, etc., but whether it pays to run good cane-juice to the liquor cistern, instead of converting it to sugar and molasses is to me a very problematical question; that this is done, however, cannot be denied. Bookkeepers are expected to make heavy rum crops; the more rum made in proportion to sugar shipped, the greater their merit.
But can you keep that up when you cede control of the mill?
Burton finally gives us the closest thing to trash:
Cane tops—that is, the plant and top without the leaf, cut up in a top cutter—if spread three or four inches deep in the mixing cistern, and allowed to remain there twenty-four hours after having had a puncheon of molasses mixed with it, makes an excellent ferment, imparts a fine flavour to the wash, and destroys any acidity that might be in the mixing cistern.
Four inches deep!
By 1882, an anonymous author, describing production of the Vale Royal Wedderburn, is turning their mixing cistern into a cane trash porridge:
Go on drawing down until the mixing cistern is nearly full and while filling with skimmings get all the finely powdered cane trash obtained from the mill bed and liquor strainers, and throw into the mixing cistern until the contents appear as it were a half solid half liquid mass.
What could the value be? Percival Greg feels his experience with fission yeast no. 18 has a connection with that of the Vale Royal author. Greg’s work eventually explores cane trash:
If however the skimmings before being set up be run on to a so called “dirty cistern,” i.e., a cistern filled with cane trash, and be there allowed to undergo a preliminary “souring”, and this will certainly comprehend an acetic fermentation, then the fruity acid will be set free provided that the heating with lime in the Boiling House has been efficiently carried out.
A lot is going on. What is the active ingredient? Is there one or a few particular things working in concert?
It is probable also that the nature of the aroma produced will vary with variations in the management of the trash cistern. Thus if the liquor already present in the trash cistern be fermented low down, that is, if it contain much alcohol, and if the fruity acid be set free by a simultaneous acetic fermentation (and there is no doubt that many kinds of fermentations go on at the same time in the trash cistern) it will tend in its nascent form, i.e. at the moment at which it is set free, to combine with the alcohol to form its characteristic fruit ether, whereas if little or no alcohol be present it will probably come into the rum in its free state and the aroma will be different. We shall also understand how if the salt of the fruity acid escapes decomposition in the mixing cistern, the fruit ether may still be formed by letting the liquor die down in the fermenting cistern until a “creamy” head appears. The conditions at the conclusion of an alcoholic fermentation are eminently favorable, in tropical countries to an acetic fermentation, which then plays the part I have indicated. I have on several occasions microscopically examined these creamy heads and find them to be largely composed of acetic acid bacteria. It is evident also that if the trash cistern is to be used with its maximum effect as regards the production of the aroma, i.e., for producing really aromatic rums, that two cisterns must be used, that the juice must be allowed to sour for at least 24 hours and the juice of one souring must on no account be mixed immediately previous to fermentation, with freshly tempered skimmings. That the juice should rest for a considerable period in the mixing cistern is evident, because the object is in this case to develop acidity, and that is should not be mixed with freshly tempered skimmings seems equally evident because the excess of temper lime present in the skimmings would neutralise the fruity acid if any had been sent free, and just lock up the aroma again. As to the amount of influence to be ascribed to this fruity acid or its ether in producing high class rum it is almost impossible to say but I have often ben able to detect its presence by smell in good rum.
Percival Greg is starting to ramble. He said trash and I followed, but he made no connections to trash as an active ingredient.
Taking into account then the influence exercised by bacteria and their products, it is easy to understand that if we depend upon the trash cistern to furnish us with a supply of vigorous yeast to produce a fairly rapid and satisfactory attenuation, we shall be disappointed. They yeast will have been already weakened in its fermentative and reproductive capacities, and consequently the fermentation will be slow, that is to say the rate of attenuation and the yield of alcohol will be unsatisfactory. I am fully aware that trash cistern are worked with the result of giving a fair average attenuation and yield viewed from the Jamaica standpoint, but then they are worked more on the lines of a “mother” cistern, i.e. are prevented from going radically sour by being always kept alive by periodical doses of molasses and dunder; but in these cases I have not seen real high priced rum produced.
He keeps going if you are interested. We see admission that the trash cistern is used as a source of yeast and also that molasses and dunder are sometimes dosed. However, we also hear that it may not be the best system.
On the next page, Percival Greg invokes sour mash Bourbon production and the need a of similar structured rational process for rum production complete with a fully though out yeast mash. It is well worth continuing with Greg’s proposal of marrying pure culture yeast growth to the trash cistern. The possibility is opened that another yeast besides fission yeast no. 18 may be an aroma producer.
Percival Greg keeps going and gives us the one liner:
And the trash cistern has long been considered as the sine quâ non by practical men in the production of high flavoured rum.
Collingswood gives us a reference from 1907:
The raw materials employed in making common clean rum consist of molasses, “skimmings,” and “dunder.” The first named needs no special description. “Skimmings” consist of the scum which rises during the boiling of the cane juice. Before use they are allowed to undergo acid fermentation, either alone or in presence of the crushed canes (or “trash”).
This is a second hand production account but it appears even common clean rums saw skimmings soured over cane trash. Here, you may be lead to believe the trash is just a scaffold for whatever organism sours, very much like the cork and wood chips in the quick vinegar process.
Collingswood then gives us the full trash sandwich and besides the soured skimmings as a starter, flavour is eventually added which also incorporates cane trash.
In making flavoured or German rum, the same materials are used as in the case of common clean rum, with the addition of what is technically, termed “acid” and “flavour.” “Acid” is produced by fermenting cane juice and allowing it to acidify by standing in contact with cane trash and sludge from the fermenting vats. “Flavour” is prepared by fermenting cane juice in contact with cane trash, dunder sediment and sludge from the fermenting vats being added at various stages of the process. The fermentation of this product is largely anaerobic, and butyric acid is a characteristic ingredient.
Acid or flavour resembles culinary vinegar more than does soured skimmings. My bet is that soured skimmings may have had a few g/L of volatile acidity where as Acid may have been 3% or 30 g/L of volatile acidity which is still lower than culinary vinegar’s typical 5%. Soured skimmings would have us thinking in the pH scale because the souring creates clean conditions for yeast (think pH 4.0), very similar to the sour mash Bourbon process, whereas for acid, we would be thinking in terms of titration because we are concerned with g/L of free volatile acidity.
Out of time!