Some analyses of genuine Jamaica rums., 1907.

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WILLIAMS (W. COLLINGWOOD). — Some analyses of genuine Jamaica rums. J. Soc. Chem. Ind. XXVI, 498-500, 1907.
[Society of Chemical Industry (Great Britain)]

This was another very cool reference from Kervegant that I just recently unearthed. I transpose these to blog posts to make then globally available to the distilling community because for many countries public domain content may still have a restriction. This paper analyzes samples supplied directly by Charles Allan in Jamaica so no doubt Hampden was featured! One of the coolest admissions we see from the authors regards higher alcohols: “This proportion is relatively low, being on an average less than half that usually present in pot-still whiskey.” Its 1907 and the Jamaican rum industry still used spontaneous fermentation via fission yeast and these numbers back that up. Fission yeasts on average producer far less higher alcohol than a budding yeast despite the tropical temperatures.

We also get some candid opinions of quality from the authors. They describe three samples as “remarkably poor specimens” of Jamaica rum. That can be hard to imagine if you are taught to assume anything pot-distilled will be heavy. All they had was pots back then. However, we now know garbage in/garbage out and that fermentation dictates the potential of everything. The authors then note that three ferments were not very good relative to their esters and that two were far better than their esters elude. How can that be explained? Well interestingly, the three poor ones have twice the higher alcohols as the two really good ones. Does that imply that the good ones are from fission yeasts and the bad ones budding yeasts? Another explanation may be that some have rum oil and radiance while the others do not. In my own experience, significant esters without rum oil are kind of thin and hollow.

Interpreting the data can be challenging, but what I’m going to personally bring to my work from these data sets is the titrateable acidity numbers. I should be able to compare role models I evaluate to the historic numbers and see how they stack up.

In 1907, inconsistency ruled the day, but did that ever change? Subtract all the column stills and where is Jamaica rum today?



Having recently received direct from Jamaica a number of samples of rum produced on various estates in the Island, it appeared to me that the results of their analysis would be worth placing on record, especially as very few such analyses have been published hitherto. The samples were sent to me by Mr. Charles Allan, B.Sc., late Fermentation Chemist to the Sugar Experiment Station of the Jamaica Board of Agriculture, and their genuineness is authenticated by him. I am further indebted to Mr. Allan for information as to the process of manufacture, which I will briefly describe before discussing the analytical results.

Jamaica rums are broadly classified for trade purposes in two distinct groups, viz., (a) common clean, ordinary drinking rum; (b)“flavoured” or “German” rum, used solely for blending.

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”). “Dunder is the spent wash from the stills. The unfermented wash when set up contains from 10 to 15 per cent. of sugars, and, owing to the use of the sour skimmings and dunder, a considerable amount of organic acids (principally acetic, propionic, butyric, and lactic) is also present.

Fermentation is very slow, occupying five or six days. Alcoholic fermentation results from the action of yeasts from the cane rind, but as fermentation proceeds acid forming bacteria multiply at the expense of the yeasts, ultimately entirely supplanting them.

The still used in Jamaica is invariably of the pot-still type, heated sometimes by direct fire heat and in other cases by steam coils.

After leaving the still, the vapours pass through one or two rectifiers, which are charged with “low wines” and “high wines” respectively. Should there be only one rectifier, the high wines are returned to the still itself. The first portion of the distillate constitutes rum, and is of about 40° 0.P. when collected. The second portion is the high wines (about 20° 0.P.), and the final fraction, low wines.

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.

The skimmings are also subjected to a preliminary fermentation in contact with cane trash, lasting some days, and the final fermentation after the wash is set up lasts 14 or 15 days. Distillation is then conducted as in the case of the common clean rum. The development of bacterial action, in addition to yeast fermentation, appears to be an essential feature of the manufacture of Jamaica rum, and the former is especially encouraged in making flavoured rums. In this respect the Jamaica process differs essentially from that employed in Demerara and Trinidad, whereby what is known commercially as “Demerara rum” is produced. In this case the fermentation is rapid, and due solely to yeast action, bacteria having no time to develop. The Demerara fermented wash is also in many cases distilled in patent stills, though by no means invariably so.

[The wording above almost seems to imply that a rum produced in Trinidad from the quick process may be referred to on the market as a “Demerara rum”.]

The Demerara process is undoubtedly better amenable to scientific control as an alcohol industry, but the product is much inferior to most rums of the Jamaica type. I shall recur to the analytical differences between Jamaica and Demerara rums at a later stage.

Analyses of the samples.—The alcoholic strength varied from 21° to 44° O.P., the majority lying between 35° and 43° O.P. Three of the samples (Nos. 9, 18, and 26) were uncoloured, and consequently practically devoid of solid matter. In the rest of the samples, the solids varied from 0.14 to 1.16 grms. per 100 c.c., the average being 0.4 for the whole series. The remaining items of the analyses are expressed as grams per 100 litres of alcohol (i.e., parts per 100,000), in terms of a typical compound of each class, in accordance with the usual practice.

In the “common clean” rums, total acidity (as acetic acid) varied from 30 to 155, with an average of 78.5, while volatile acidity varied from 21 to 146, averaging 61. In the “flavoured” rums, the acidity is rather higher, averaging 102.5 for total and 95.5 for volatile acid. The total acidity was determined by direct titration, volatile acidity by deducting the acidity of the dried solids from the total.

[These numbers are easy to figure out via titration and I’ll have to make some comparisons going forward.]

For the estimation of volatile esters, higher alcohols, furfural and aldehyde, the spirit was first diluted so as to contain about 50 per cent. alcohol by volume, and in the case of coloured samples 200 c.c. of the diluted spirit was distilled until 180 c.c. had passed over. The distillate was made up to 200 c.c., and the exact alcoholic strength taken. In the case of uncoloured samples, distillation was dispensed with, the analysis being at once proceeded with after ascertaining the exact strength of the diluted spirit. I have found by repeated trials on many occasions that the simple distillation of 9/10 is sufficient to bring over the whole of the volatile esters, higher alcohols, and furfural, and it is in my opinion both unnecessary and undesirable to complicate the analysis of spirits by employing more elaborate methods of distillation.

The volatile esters were estimated in the distillates by saponification with caustic soda in the usual manner, employing a soda solution of which I c.c.=0.025 grams of ethyl acetate. In the “common clean” rums the esters, expressed as ethyl acetate, were found to vary from 88 to 1058 grams per 100 litres of alcohol, averaging 366.5. The sample No. 20, showing 88 parts, is quite exceptional, and this sample, as well as Nos. 4 and 12, were remarkably poor specimens of Jamaica rum, possessing but little of the characteristic aroma and flavour of that spirit. In the “flavoured” rums, the esters varied from 391 to 1204, with an average of 768.5.

The relatively high proportion of esters in Jamaica as compared with other spirits is due to the acidity of the fermented wash and of the “dunder” mixed therewith. The samples are tabulated in the order of their ester content. It is not suggested, however, that this is an absolute index of quality, though it appears to be the case that, broadly speaking, rums containing the higher proportions of esters command higher price—provided of course that the esters have been produced in a legitimate manner.

The “higher alcohols” were estimated by the Allen Marquardt process, and are expressed in terms of amyl alcohol. The proportion found varied from 46 to 150 grams per 100 litres of alcohol, with an average of 98.5 in the common clean rums; and from 80 to 144 with an average of 107 in the flavoured rums. This proportion is relatively low, being on an average less than half that usually present in pot-still whiskey.

[The last sentence is an absolutely remarkable admission and conforms to all of my experience with the birectifier comparing fission yeasts to budding yeasts. The difference in higher alcohols can be sensed quite obviously in fraction 4 of the birectifier fractions. No elaborate titration necessary.]

Furfural and aldehyde were estimated colorimetrically by comparing the tints produced with aniline acetate and Gayon-Schiff reagent respectively, with standard solutions of furfural and aldehyde in 50 per cent. alcohol, The proportions found were extremely variable, and it does not seem possible to base any very definite general conclusions upon them; but a high figure for aldehyde seems often to be associated with a less satisfactory rum. For example, samples 15, 16, and 17 are, in my judgment, not worthy of the relatively high position they occupy in the classification on the ester basis; while, conversely, Nos. 5 and 13 are, in my opinion, better rums than the ester value, taken alone, would indicate.

From the description of the manufacture already given, it will be gathered that the term “flavoured”, as applied to Jamaica rum, does not imply that any favouring material is added, but merely that a special method of fermentation is employed with a view to the development of flavour in the finished product. Haphazard as the process is, it is not surprising that the desired result does not seem to be attained with certainty, and as a matter of fact there appears to be no hard and fast distinction between the two classes.

Both in chemical composition and in strength and quality of flavour, I find they overlap—the best samples of “common clean” of this series being, in my opinion, superior to some of the “flavoured” rums. As already mentioned, the flavoured rums are not used for drinking as such. They command a relatively high price, and are mainly exported to Germany (hence the name German rum), where they are used for flavouring neutral spirit in imitation of genuine Jamaica rum.

I have already referred to Demerara rum. This article, produced as it is by the distillation of fermented cane molasses, is undoubtedly entitled to the name of rum, but is of relatively poor quality and considerably cheaper than Jamaica rum.

A few samples of Demerara rum from bond which I examined a year or two ago gave the results set out in Table C, and, from a detailed report by Prof. Harrison, of Demerara, published in 1904, I find that he gives the mean proportion of esters in Demerara rum as 70 parts per 100,000 of alcohol for vat stills, and 45 parts for continuous stills.

In Demerara rum it appears that one has a most suitable material for blending with flavoured Jamaica rum. The former, though approaching plain spirit in many cases, is of a clean and wholesome type, and is prepared from a legitimate source of rum in a British Colony. In order to give Demerara rum the character which it lacks, flavoured Jamaica rum is the very thing required, and it would seem preferable that such an employment should be found for it rather than that it should be sent to Hamburg to flavour potato or beet spirit, and thus illegitimately compete with the Jamaica planters in their own market.

In conclusion I desire to express my thanks to Messrs. W. H. Roberts, E. G. Jones, E. Garratt, and H. E. Gresham for their assistance in connection with the analytical work described in this paper.


[You cannot tell much from a single sample, but it makes you wonder if no. 20 saw the most coloring to compensate for it being the blandest.
The author thought no. 4,12, and 20 were not recognizable as Jamaica rum.
No. 15,16, and17 were not as good as their ester content would imply.
No. 5 and 13 were better than their esters let on.
If we look for a pattern in the fusel oil, 5 and 13 may be fission yeast ferments while 15,16,17 may be budding yeast ferments.]


The chairman said that it was satisfactory to learn that Mr. Williams was able to trace a connection between his figures and the qualities and values of the various samples. He had not said, however, whether he was able to trace any connection between rums of low acidity and ester values and individual factories. Did any given factory produce a particular grade of rum, or was it more or less chance whether a high or a low grade product appeared? Had Mr. Williams any information on that point?

Professor Donnan thought the existence of a bacterium in rum of considerable alcoholic strength had been recently investigated. Did the author think it would be possible in the case of a liquid so rich in alcoho?

Mr. Collingwood Williams said that he thought the actual production of the esters would occur almost entirely after the heat was applied to the stills. The nature of the esters was a very interesting question, but one that could be determined only if sufficient material were at command. The highest of the figures for the flavoured rums would represent about 1 per cent. of esters in the sample. The amount is not large absolutely, and when one had only small quantities of material to deal with, one could not conduct a very extended investigation into the nature of the actual bodies themselves. He had, however, ascertained the mean combining weights of the acids combined as esters in four of the samples and had obtained the following results:—

No. 1, 66; No. 9, 71; No. 18, 69; No. 22, 68; in all cases indicating that the esters were not merely ethyl acetate. From the flavour and aroma there was no doubt that esters of the higher fatty acids were present.

As to the possibility of any bacillus living in the rum itself, he did not think that anything happened to the rum from bacterial action after it was once distilled.

No doubt by the addition of suitable cultures to the unfermented wash, rums of different flavours might be produced almost at will, but he was quite certain that the Jamaica planter had not reached that stage. It seemed that some estates can make these flavoured rums, while others cannot. Judging from the descriptions, a very complex mixture of organisms must exist in the fermentation stages, and it was quite impossible to say what particular bacillus produced tho observed results. Bacillus butyricus and allied forms producing butyric acid certainly existed in the tanks and cisterns, and were especially found in the material used in making flavoured rum.

The question of the chairman as to the variations on the estates was sufficiently answered by the enormous variation in the figures obtained. The planters were only beginning to learn how to control their manufacture. A great deal remained to be done, and no doubt could be done by careful supervision.

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