Kervegant Chapter XVI Organoleptic Examination and Appraisal of Rhums

Kervegant Chapter XVI Organoleptic Examination and Appraisal of Rhums:

Pages: 410-428


[The birectifier and Micko’s method of fractional distillation becomes a big feature of this chapter.]


The tasting of eaux-de-vie involves the appraisal of odors or perfumes (olfactory examination) and that of flavors (taste examination or tasting itself). It can be done on the product as is, or after dissociation of the elements of the aroma by means of certain physical or physicochemical processes. Some authors advise to taste first, so as not to be influenced by the results of the chemical analysis, and others when the analysis is completed, to confirm or supplement the information provided by it.

[dissociation involves methods such as birectifier fractioning to better sort congeners or techniques such as the sulfuric acid test to chemically dissociate certain congeners. A new one I have yet to explore is birectifier fractioning after saponification of the esters.]

Tasting of spirits.

“Tasting”, writes L. Mathieu (1) “is not so simple a transaction as it seems at first: the appraisal of the taster is the result of the operation of a complex set of organs, of the senses of sight, smell, taste and brain.”

(1) Rev. Scientifique XLVIII, 390, 1910.

The value of the results obtained will depend not only on the sensitivity and perfection of the physical work of the tasters, but also on temporary causes that may influence the sensation or perception.

The subject’s “personal constant of sensitivity”, developed by heredity, education or exercise, and maintained by constant training, plays a considerable role. “The tasters with chemical notions and the chemist experienced in the art of tasting have a very great superiority over professionals that are simply chemists or tasters. The work of interpreting analyzes or tasting is naturally easier for the first one and the results more precise. It is conceivable, in fact, that a taster doubled as a chemist relates impressions exactly to the bodies which produced them: the field of their mental experience is more considerable, and has at their disposal a sum of accumulated sensations more abundant and, consequently, they are much less likely to be mistaken, in the identification of the cause having provoked this or that impression, than a taster ignorant of the nature of the acting body and who can not relate it to its true cause. In the same way the language of the first taster is more precise, calling things by their name; that of the second more imaged and more personal taking terms of comparison in their usual knowledge “(Mathieu).

Among the causes which momentarily influence the operation of tasting, we must first point out the state of health of sensory organs. Thus the coryza, or inflammation of the olfactory mucosa, the sub-normal state of the tongue in the mucosal states impede any functioning of these organs.

But, moreover, the impressions and the mental work can, separately or simultaneously, undergo influences which, by modifying the sensibility of the organs, have the effect of distorting the judgment of the taster. Mathieu lists the following main influences:

1 °) Variability of sensitivity. — At the beginning of a tasting session, the impressions are often obtuse: the sensory organs reach maximum sensitivity only after one or two samples. Also, it is appropriate to return to the first impressions, corresponding to the start-up period.

Conversely, sensitivity is dulled by repeated excitations; more violent excitations are needed to produce the same impression. Therefore, only a limited number of samples should be consumed per session. For the assessment of alcohols, the Swiss Régie recommends to operate only 4 or at most 5 consecutive examinations and, if there is a greater number of samples, to take a break of at least one hour.

If you first taste a product with a high intensity of flavor or bouquet, you will not see the nuances of a less aromatic product. The sensory organs impressed by a violent excitation quickly lose their sensitivity, to be impressed only by stronger excitations. Therefore, the samples to be examined should be graduated, in order of increasing taste intensity.

Lastly, the fatigue of the sensory organ, like general fatigue or that of any organ, has a profound repercussion on the sensibility of impressions.

(2) Variability of perception – Attention has a considerable effect on the intensity of perception, whether it has not been awakened or has been distracted by some external cause. Hence the need for the taster to focus all his attention on the points he must look for and at the same time to remove any cause of distraction (conversation, noises, etc.) The tasting will be performed preferably in a special well isolated room.

Tense attention can also distort perception, exaggerating our sensitivity and giving the object that has excited it an abnormal importance. It is even possible that we perceive non-existent impressions and that we are victims of real illusions, not only under external suggestions, but also by self-suggestions. It is important, therefore, to avoid the unfortunate influence exerted by labels, opinions expressed, etc.

[Olfactory illusions are not well acknowledge but they are quite common.]

Memory plays an important role in perception, since we compare, consciously or unconsciously, the sensations received with those previously experienced. The comparison will be all the more perfect as the sensations recalled will be more precise. The ideal is to be able to immediately compare the impressions, that is to say to proceed to the tasting with witnesses (comparative tasting).

The organ of taste is very sensitive to the influence of the preceding impressions; thus, a wine appears to be acrid if it is drunk after a sweet dish, and velvety, tasted after a cheese. It seems that there are successive impressions that are enhanced by forming contrast, as in the case of complementary colors.

[This is very special, not many people were capable of noticing these things in that era. I have written a lot about food and wine interaction and the phenomenon of contrast enhancement in space and time.]

The eaux-de-vie are made up of many sweet and fragrant substances, which simultaneously impress the taster. By paying attention successively to the various constituents, we arrive at a certain point, if one of them does not dominate excessively, to discern their specific influence. However, in some cases, impressions can be confused. This is the explanation of the practice, quite commonplace formerly, of adding certain spirits of sulfuric acid, pepper, and spicy substances to replace the alcohol too diluted by wetting.

[I have never heard of this last concept, but when I practiced the exhaustive test, I experimented with using ethanol instead of water. The water, believe it or not, seems almost distracting. It takes a certain amount of practice to get used to looking for an aroma in a heavily diluted spirit.]

If one of the impressions is clearly dominant, it prevents the perception of all the others. A pronounced moldy taste, for example, masks finding anything else. In spirits at high degree, the impression of alcohol is so violent that it no longer allows other bodies to manifest themselves. This is the reason why these alcohols are first diluted to appreciate them.

[This an attentional issue on the one hand and then a physical issue of solubility on the other.]

Habit has accepted as normal certain tastes considered by other tasters to be unpleasant or even disgusting. Thus, in the northern countries, the flavor of grain alcohols is preferred; in Germany and Switzerland the taste of potato alcohol, but looked at in France as very inferior.

[Rum has very distinct example of this. Vesouté is loved many, but historically also sees pockets of disdain. Excessive ethyl acetate in a young spirit would technically be a flaw to many, but is enjoyed in rums like Rum Fire or Wray & Nephews.]

If you sample a large number of samples, you soon find it very difficult to discern nuances. There is not only a diminution of sensory sensibility by frequently renewed excitations, but also perceptions require more and more attention.

We can compare the state of fatigue, the influence of the repletion of the stomach, either the state of emptiness is more favorable to excitability, or the exercise of organs has blunted their sensitivity and explains that tasters prefer to work in the morning, before any other occupation, when they present the maximum of sensitivity and rest.

“If I insisted”, concludes Mathieu, “on all the causes that come to influence tasting, it should not however exaggerate the importance and deduce that most often tasters are victims of illusions. The reality is that if illusions are possible, the professional who knows the genesis knows very well how to avoid them; he gives his opinion only when he feels fit, “in the mouth”. Tasting is in fact a very scientific operation, and it is not surprising that it gives indisputable results when it is directed rationally, that is, with tasters with personal constants of sensitivity and psychic work as high as possible, put in conditions where their passing coefficient will give the maximum of perfection to the functioning of their organs”.

[This is an extraordinary statement. For a long time it was though olfaction was the only sensory modality that was not subject to illusion, but it turns out it may be quite the opposite.]

Practice of tasting.

The tasting of eaux-de-vie is usually done in a special glass, with thin walls, narrowing at the top (frustoconical glass, or swollen at the base and ending with a narrower cylindrical or frustoconical part), to concentrate the smells in the nose. The glass is sometimes graduated, to make it easier to work the dilutions with water.

Tastings must be done in a special room, isolated from others, showing no smell due to wood or paint. Avoid smoking or chemical manipulation. The glasses, which should not be used for any other purpose, will be kept dust-free in an oak cabinet, held on a wooden support. Do not use the tree of any other fragrant wood, the glass easily absorbing their smell. Finally, the tasting room will be well lit, as much as possible by a wide bay window to the north, to better appreciate the color and clarity of the eaux-de-vie.

The best time to taste is in the morning, around 2 hours after breakfast. In the afternoon, the sensitivity of smell and taste is greatly reduced, especially among smokers and those who have consumed spicy foods. It is essential to avoid smoking before tasting.

The olfactory examination must precede that of tastes, otherwise the discrimination of odors is less clear. When, for any reason, the spirit is tasted beforehand, it is important to rinse the mouth thoroughly before performing the olfactory examination.

The odor of ethyl alcohol can mask other odors, when they are in small quantities, the perception of smell is often unclear. Several ways are used to detect perfumes more easily.

One of the simplest is to pour a few drops of liquid in the palm of your hand, then to rub the two palms together to cause the evaporation of alcohol. There remains a bouquet that is easier to appreciate. This is the most common process used by distillers. The “fat”, or foam that occurs by friction, also reflects the richness in higher alcohols and esential oils: it is generally all the more abundant as the eau-de-vie is more aromatic.

You can also use a bottle that is filled to one-tenth with eau-de-vie. After having covered the mouthed with your finger, you stir to hasten the evaporation: the empty space becomes saturated with vapors, that you smell to perceive the bouquet. It is preferable, however, to operate with a conical, thin-walled vessel, into which a few drops of spirits are poured for examination, which are evaporated by the heat of the hand, by impressing the vessel with a gyratory movement.

[Some forms of chromatography only look at the compounds that gather in such empty head space.]

Another method consists in pouring the brandy into a tasting glass, then emptying it and covering it with a sheet of paper laid flat. After 12-15 hours, when the alcohol has evaporated, we feel the contents of the glass.

[Arroyo used versions of this and used a watch class cover instead of paper. The spirit evaporates slowly under that cover. A greasy oil can often be detected with the finger at the bottom in full flavored spirits. This oil may be the “Bauer oil” described by Kervegant in a previous chapter.]

Taste examination may be carried out on the product as such, in the case of brandy or aged spirits with an alcoholic strength not exceeding 50 °. But if the spirit has more than 60 °, it is essential to dilute it beforehand with water.

For this purpose spring water, fresh or warm, is used so that the spirits are reduced to a strength of about 30° and a temperature of 25° -30° C. Distilled water is not suitable. The contents of the glass are mixed thoroughly and, while the liquid is still sparkling a little, we notice the fragrance, by advancing your nose as deep as you can in the glass. Then we notice the taste, putting in the mouth a small quantity of liquid which we then spit: we note the impression on the palate, the taste and the after-taste.

Even if the eau-de-vie is at the degree of consumption, it is good to enjoy it with a volume of warm water. Dilution facilitates the release of odors and sometimes allows realizing the wealth of higher alcohols and essential oils: heavily loaded with these products, an eau-de-vie is cloudy by the addition of water.

Rocques advises making the following four observations: the smell and taste of the eau-de-vie as it is, then the smell and taste of the eau-de-vie diluted by a volume of lukewarm water . “It’s usually”, he says, “this second part of the tasting that gives the most conclusive results.”

In the Swiss official method, taste testing is carried out firstly on the initial product at 15° C, then on the diluted spirits up to an alcohol content of 20% by volume, at the temperatures 15° and 25°C. The olfactory examination is done in the same way, but at a temperature of 50°.

For the appreciation of rum and arak, the “grog” test is also often used. The product is diluted with hot water, so that the alcohol content is reduced to 10% or 5% (sometimes 1-2% in the case of very aromatic rums), and the odor and the flavor of this dilution, with and without added sugar. This test makes it possible to detect, more easily than tasting of the product straight, the presence of fine and delicate aromas, masked, particularly in the case of grand arôme rums, by certain esters. The volatility of ethyl acetate is also reduced by the water and the somewhat pungent odor of this esters is attenuated.

[This simple test is a lot more profound than you think. I advise anyone to try it.]

Research of aromatic substances.

Different processes have been recommended to dissociate the elements of the bouquet and better highlight the aromatic substances.

Hager (1882) proposed adding to the spirit, previously diluted with an equal volume of water if it is more than 60°, 6% glycerine. Filter paper is soaked with the mixture, and let to evaporate in the open air. After departure of the alcohol, the smell of fusel oil, retained by the glycerin, remains impregnated in the paper and is easily perceived.

[I have never heard of this. Would a coffee filter work?]

Uffelmann and Betelli stir 200 cc of spirits with chloroform, which is then separated by addition of water and decantation. The chloroform is evaporated and the residue is felt. By treating the latter with sulfuric acid and sodium acetate, we detect amyl alcohol, by the smell of amyl acetate, up to a dilution of 1: 500,000.

[Amyl alcohol is convered to an ester to evaluate it.]

Sulfuric acid test — Wiederbold (1), to differentiate true rum from artificial rum, recommends treating 10 cc of the product with 3 cc of concentrated sulfuric acid. The initial aroma of rum disappears and a particular smell develops, reminiscent of petrol. This smell, which appears even when the eau-de-vie is split with neutral alcohol in the proportion of 1 to 10, persists for at least 24 hours. It never happens with artificial rums, whose aroma disappears quickly and completely. If the spirit contains a high proportion of ethyl acetate, to detect the smell, it is necessary first to get rid of this ester by distillation (Schaeffer (1)). German chemists frequently use the sulfuric acid test to differentiate authentic rums from imitation products.

[It is absolutely spectacular to find the first origins of this test and then a second reference to perhaps squeeze more information from it. I have not tried systematic dilutions with ethanol, but I have revived the aroma diluting with water after a few days. I have not removed ethyl acetate first, but the birectifier provides an easy means of doing it. Kervegant so far has not mentioned the brimstone aroma which can develop with the test. I am curious about performing the test with another type of concentrated acid which may avoid the brimstone. I suspect sulfuric acid was chosen for price and availability.]

(1) Chem. News XI, 84, 1865.
(1) Chem. Ztg. XLVI, 254, 1922. [These notes were split across two pages.]

Arroyo recommends leaving sulfuric acid treated rum (10 cc of rum placed in a 25 cc test tube and adding 3-5 cc of concentrated sulfuric acid) to rest over night and examining the product the next morning. The complete disappearance of the aroma indicates a spirits lacking rum oil; a slight persistence, a small proportion of rum oil; and an accentuated aroma, a good product. Sometimes the primitive aroma is transformed into an unpleasant odor; this can be caused by the presence of sulfur compounds in high proportions in the molasses used in the production of rum.

[Here, via Arroyo, we see mention of the sulfur compounds, but I really don’t believe it has anything to do with the molasses.]

Micko’s essay. — In order to separate from one another the different aromatic substances forming part of the bouquet, Micko (1908) recommends concentrating them in certain fractions. He added to 200 cc of rum, 30 cc of water, and subjected the mixture to fractional distillation, so as to obtain 8 fractions, the first 7 each formed by 25 cc and the eighth by the rest of the distillate. When the alcoholic strength of the eau-de-vie is greater than 70°, it is necessary to add 20 to 30 cc of river water and to continue the distillation. This must be pushed as far as possible: it stops only just before the residue starts to burn. Each fraction is then subjected to an olfactory examination, pouring the liquid into a tasting glass and allowing it to evaporate.

[Micko’s technique evolved quite a bit into the birectifier method. I don’t know where Kervegant got the eccentric details like using river water. Importantly it evolved to be based on a 100 ml of absolute alcohol system so that the fractions were repeatable and comparable.]

The first 2 fractions contain, besides ethyl alcohol, ethylaldehyde and the most volatile esters, such as those of formic and acetic acids. The third and the fourth do not present particular distinctive character. But in the following fractions, lower in alcohol, we find aromatic substances typical of the spirits examined. Rum contains, in the fifth and especially the sixth fraction, a very aromatic essential oil (rum oil) and a terpenic substance with a juniper odor. After the typical aromas appear, in the last fractions, low volatile materials, among other aromatic products of resinous nature which disturb the distillate; these are soluble in caustic soda and released again by acids.

Artificial rums often contain, in the sixth fraction, cinnamon oil, etc.; in the seventh and eighth, vanillin. The presence of the latter may be masked by other substances. To detect it, Micko advises shaking the last 3 fractions with 5 cc of chloroform. The chloroform is separated by addition of water and decantation, then evaporated by gentle heating in a water bath. After removing the chloroform and cooling, olfactory examination is carried out. If the perfume of vanillin, masked by that of other aromatic substances, does not appear, it is good to leave the residue, covered with a watch glass, for 2 or 3 days: at the end of this time, the foreign perfumes have evaporated or oxidized, while vanillin, less volatile, persists.

[Many of these ideas started with government scientists trying to identify adulteration but slowly the ideas were applied to improving authentic rum.]

The Micko method has given remarkable results in the appraisal of spirits and more particularly rums (Kappeler and Schulze, Luckow, etc.). It is now very much employed in Germany and Switzerland. In the latter country, where it has been classified as an official method, it is applied as follows:

“Distil slowly in a 300 cc flask, equipped with a 2 ball rectifying tube, 300 cc of eau-de-vie reduced to 40% by volume. Collect 6 fractions of 12.5 cc, operating in such a way that each of them distills in 12 to 15 minutes. Examine each of these fractions, as well as the residue of the distillation, from the point of view of aroma and flavor. For that, dilute the first 3 fractions with the double their volume and the following ones with their volume of ordinary water at 30° C, then examine the odor in 75 cc glasses, conical in shape narrowed upwards. The residue of the distillation will be used for the research of vanillin. If the typical aroma is only slightly recognizable in the fraction under examination and if it is masked by the presence of esters, add to this fraction the quantity of caustic soda 0.1 N exactly necessary for the saponification, and leave it all for 24 hours at room temperature, after which the typical aroma will be released much more clearly.”

[This protocol is a bit sloppy. It would be great to know when exactly it was published.]

Luckow (1), to obtain a more rigorous classification of aromatic substances in order of volatility, proposed the use of a small birectificator built at the glassworks of the Institute of Fermentations of Berlin. This apparatus consists of a 6-ball condenser tube equipped with a lateral condenser, which forces the less volatile vapors to be demoted into the balloon; it is connected to a Liebig condenser.

(1) Z. Unters. Lebensm. LXII, 585, 1931.


[The birectifier we sell ($1800) is a next generation 5 ball design. The fittings have also been optimized for the modern era. The thermometer ports are threaded and a ball joint is used on condenser to reduce the chance of breakage. We have already conducted extensive case studies as well as recovered and translated a lot of lost documentation.]

We introduce, in a 1 liter flask, 240 cc of spirits to be examined, previously reduced to about 40°, and we set up the birectifier, using only cork stoppers, rubber ones giving a bad taste to alcohol. Heat slowly and evenly, so that the distillation is done in 2 hours. The distillate is collected from 8 small 25 cc volumetric flasks each, without interrupting the distillation. The 40 cc of liquid remaining in the apparatus constitutes the residue, which is examined from the point of view of smell and flavor like the other fractions. The first fractions, which have a high alcohol content, must be diluted with water to perform the organoleptic examination.

[Arroyo evolved this protocol from using 96 ml of absolute alcohol as described here to using 100 ml which pushes high value congeners more neatly into fraction 5. It is interesting that Kervegant covers the birectifier in his organoleptic section. I have used it organoleptically as I suspect most other distillers well, but Arroyo performed detailed analysis on every fraction. The birectifier greatly enhances the value you can get from standard acid and ester titrations because of how it separates high value and low value esters so they can be measured separately. It also spares you other assays because of how easily it isolates congeners and increases the value of organoleptic assay. For example, with the birectifier there is no need to invest in furfurol assay. The birectifier is also a cheap way to add crude olfactometry to GCMS. The birectifier should be standard equipment in every distillery because it has a low learning curve and can answer the most questions relative to its cost.]

In Switzerland, they operate as follows:

“Distill with the birectifier 100 cc of eau-de-vie reduced to 40% by volume, to which you will have added some granules of pumice stone. Conduct the distillation in such a way that the liquid collected in the inner tube never reaches the first ball of the refrigerant. Collect in a small graduated cylinder 6 fractions of 12.5 cc each. Adjust the speed of the distillation, so that the first 3 fractions pass in time from 45 to 60 minutes. Dilute the first fractions with twice their volume and the following with their volume of drinking water, and operate the tasting in conical glasses of 75 cc.

[This is quite the unique protocol and is true micro-scale distillation. 100 cc may have been chosen because it corresponded to official government sample sizes. Pumice stone is absolutely requisite to prevent bumping. So they have 40 ml of absolute alcohol and are likely distilling the first fractions close to the azeotrope. They will have exhausted the ethanol by half way through the fourth fraction. That is an incredibly slow rate for their first fractions and likely over kill. If you distill too lowly liquid can pool in the first ball of the inner condenser. It is more of a theoretical problem than a practical one and can be expected during the 6th or 7th fraction with the protocol I favor.]

Arroyo reports that the birectifier has been of great help to him in his studies on the constitution and aging of rums. He made the following observations during his experiments:

1°) The first fraction contains most esters and aldehydes with low molecular weight. It has a penetrating odor reminiscent of a mixture of esters and very volatile aldehydes. This odor disappears after a few hours, if a small amount of liquid is exposed to the air in a watch glass.

The examination of this fraction makes it possible to be aware of the state of maturity of rums. If the product is young, the smell is pungent and the flavor irritating. As they age, the aroma and taste become less penetrating and less harsh: in a ripe spirit, the smell is delicate and the flavor is sweet.

2°) The second and third fractions consist essentially of ethyl alcohol, with small amounts of esters, aldehydes and higher alcohols. If the spirit is rich in esters and aldehydes, the aroma is delicate, but weak. If it is poor in these constituents, the odor is about that of neutral alcohol.

[The first fraction can be hard to evaluation because of how concentrated it is, but the second fraction is sort of like a jaw bone fragment to a paleontologist. It can tell you how massive the pre-historic crocodile was… I have always had extremely neutral 3rd fractions except in the case of fine tequila and a 20 year old Hampden rum.]

3°) The fourth fraction contains 65 to 70% of the higher alcohols present in the sample. It has the characteristic smell of fusel-oil, unless the spirits are rich in rum oil. In the latter case, the smell of the fusel is partially masked by the scent of rum. It is a transitional portion, which contains the last bodies of high volatility and the first bodies of lower volatility.

[I don’t know where the very last statement comes from which makes me think there are Arroyo documents I haven’t seen or Kervegant corresponded with Arroyo directly. The ability of rum oil to mask fusel oil shows how powerful it is to the sensory matrix and why it can allow you to distiller lower if it is present.]

4 °) In the fifth fraction pass most of the esters and aldehydes with high molecular weight and boiling point, at the same time as most of the rum oil. The volatile acidity undergoes a sudden increase. The liquid is cloudy and has, after rest, oily supernatant droplets.

[What we learned in another chapter from Kervegant is that these droplets may not be rose ketones themselves but rather what was called Bauer oil and is likely highly correlated. The reduce the Bauer oil in the hunt for rose ketones, the next experiment may be to saponify the esters before conducting birectifier distillation.]

It is the most important fraction from the aromatic point of view, which contains the characteristic substances of the bouquet of the spirits examined. It has the pronounced and persistent scent of rum oil. This perfume persists in some cases up to 15 days, after the liquid, placed in a glass, has apparently been evaporated.

[I have observed this at roughly 15 days with the rums from Hampden.]

5°) Fractions 6, 7 and 8 are very low in ethyl alcohol and have a high acidity. The smell, especially that of fraction 6, is reminiscent of the 5th fraction. Quite often, these 3 fractions, mainly the 7th and the 8th, contain substances with an unpleasant odor, more or less masked by the essence of rum as well as esters and aldehydes with a high boiling point, which one also meets in these fractions in higher or lower proportions.

We give below some of the results obtained by Arroyo, in the fractional distillation of various rums:

The rum samples above, aged for 2 years in oak quarts, had the following chemical composition: [assuming a quart is a quarter cask]

The same author obtained the following aromatic persistence indices (average of 6 trials) for the different fractions of Puerto Rico rums:

[The persistence index is quite a powerful organoleptic test for quality.]

[Keep in mind, these aren’t the dilutions numbers for parts of rum, but of absolute alcohol. This allows the numbers to be standard no matter what the starting alcohol content of the sample was. I discuss that further here.]

Quantitative tasting.

Wüstenfeld and Walter (1) have described, under the name of quantitative tasting, a method of estimating the intensity of the aroma, based on the determination of the greatest dilution of the spirit for which the aroma is still perceptible. The force, or vinosity, of the eau-de-vie is the proportion of water that must be added to 1 cc of the original sample, to reach the “taste threshold”.

(1) Korr. der. A. T. L. XVII, 29, 1926. [We need this paper!]

[This is an extremely powerful idea and may stand in for some overly complicated and expensive titrations such as fusel oil if you isolate it with the birectifier.]

In the case of rum and arrack, the force test is performed as follows:

[Elsewhere this has been referred to as the exhaustive test which is the name I generally acknowledge.]

We dilute, with regular water and at room temperature, 0.1 cc of the spirits up to 50 cc. We take successively this solution 0.25, 0.5, 1, 2, 2.5 cc, which is brought to 50 cc, which corresponds to dilution ratios ranging from 1:100,000 to 1:10,000. The solutions thus prepared are subjected to tasting, starting with the most diluted sample and progressively remounting the series. We stop at the sample which presents, for the first time, in a clear way, the smell and the characteristic flavor of the rum. The corresponding dilution ratio is the numerical expression of the force of the eau-de-vie.

[I’ll have to revisit this and explore the numbers to see if they are likely in terms of absolute alcohol. I suspect this was designed for grand arôme rums sought out by German buyers. A stock amount is first diluted to 50 cc to make it easier to split further then it is split again. This is much easier in the era of the automatic pipette. Notice that you also start from most dilute and imperceptible until the aroma turns on. I prepare mine double sized in 100 ml volumetric flasks which are suitable for a tasting panel of roughly four people. I also keep a tasting glass of plain water to alternate from between every taste, that way I am refreshed to a baseline of neutrality. You are almost better at detecting it passively than actively. Olfaction is more subject to illusion when active rather than passive. Drinking a glass of wine is active, while noticing aromas from a bakery as you walk down a street is passive. We actually learn aromas best passively. This test may be even more powerful than GCMS for understanding the quality of extremely small amounts of historic samples. It should be carefully conducted anytime a historic sample is opened. Keep in mind, the most stretchable odor active molecules in a spirits are rose ketones and rum can have more than any other spirit.]

In practice, the series of dilutions to be prepared will depend on the intensity of the aroma of the spirits being examined. For grape eau-de-vie, much less aromatic than rum, dilution rates will be less. What matters is that at maximum dilution the presence of the spirit is no longer perceptible.

The test can be carried out not only on the original spirits, but also on the products obtained in the fractionation by the Micko method. Although the first very volatile parts of the distillation, which are not very characteristic, are not easily diluted, interesting indications can be obtained with fractions 4, 5 and 6. However, in the case of rums and arak, best results are achieved by the treatment of the product as is.

While the dilution ratio corresponding to the “taste threshold” is generally understood for grape eau-de-vie, between 1:200 and 1:400 (sometimes 1:100), it rises in grand arôme up to 1:100,000. Its normal value is 1:25,000 for Jamaica rum, and 1: 16,700 for araks.

[This is why rum can be the greatest of all spirits.]

Wüstenfeld and Luckow proposed the following scale for rum appraisal:

It should be noted that the vinosity thus determined is much greater than the possiblities of splitting the spirit with neutral alcohol, because of the numbing effect of alcohol on the taste nerves. Previous authors noted, for example, for a sample of rum, that the force of 1:100,000 in water, fell to 1:1,650 in alcohol at 40°, a decrease of 60 times. The same phenomenon is observed for the different aromatic substances. Thus, the perfume of vanillin, barely perceptible at a dilution of 1,250,000 in 40% alcohol, is still detectable at a dilution of 1: 4,000,000 in water.

Vinosity, which is related to the level of heavy esters contained in spirits, does not necessarily reflect the quality of the eau-de-vie. In fact, rums of great force are rarely classified as high quality products, the fine and delicate aromas are masked by the violent scent of esters.

[grand arôme]

Arroyo has somewhat modified the technique of Wüstenfeld and Luckow, replacing the distilled water that gives a flat taste to the rum solution, with 40% neutral alcohol. He uses, for the test, graduated tasting glasses of about 150 cc. of capacity.

[What Arroyo did was use ethanol for the the first pre-dilution stage that way the product would be shelf stable and could be stored and recalled again in the future. For the other more significant dilutions he used water.]

The basic solution is prepared by introducing into the glass, using a micro-pipette, 1/10 cc of the rum sample, and filling at mark 50 with a solution of neutral alcohol in ordinary water. Aliquots of this basic solution are then used to determine the “taste threshold”.

Arroyo calls the “persistence index” the dilution ratio needed to reach this threshold, and proposes the following classification scale for raw rums:

Vegezzi and Haller (1) proposed using the absorbent charcoal property for aromatic materials to determine the vinosity of eaux-de-vie. As this absorption is a function of the nature of the coal, reaction time, procedure, etc…, it is important to operate under strictly controlled conditions. The Vegezzi and Haller method is applied as follows in Switzerland:

(1) Mitt. Lebensm. Hyk. XXIV, 21, 1933.

“Shake for one minute three portions of 10 cc of eau-de-vie, reduced to 40% by volume, with 0.1, 0.3 and 0.5 gr of animal bone black (Carbo animalis purissimus Merck), and filter immediately. Perform a quantitative tasting, diluting 1 cc of each of the filtered portions with 25, 50, 100 and 200 cc of 30° drinking water, and examine the odor. Perform this test in 75cc tasting glasses after allowing the product to sit for one minute. Note the dilution at which the smell is still noticeable and the one where it is no longer.”

[Kervegant really leaves us hanging on what this method achieves. Before I finished reading it, I thought you would absorb something then de-sorb which I have heard can be used to make fruit essences from juice. This method could just remove a layer of distraction from the sensory matrix and it is easy enough to try. It may be aimed at new make spirits that have “hog tracks” obscuring their quality.]

Comparative value of chemical analysis and tasting.

Much has been discussed about the respective value of chemical and organoleptic methods for the classification of spirits and the search for forgery.

Tasting was, until about 1880, the only process used to estimate the value of spirits, and it has remained to this day almost the only one employed by traders and distillers. The indications it provides are unfortunately not very rigorous. The taster draws their conclusions on personal and fleeting impressions. Two tasters may not find the same analytical results. A given operator sometimes even reaches somewhat different conclusions, in the assessment of an eau-de-vie made several days apart, their mucous membranes not always having the same sensitivity or being able, for a reason or for another unfavorably impressed.

Chemical analysis is often considered to provide more precise indications which constitute, from a legal point of view, a basis of assessment which does not support discussion. However, its relatively coarse processes do not allow accurately differentiating the complex constituents of the aroma, and therefore to decide on the intrinsic value of the product. On the other hand, the variability in the composition of spirits, particularly accentuated in the case of rums, makes it very difficult, if not impossible, to fix minimum and maximum figures enabling the chemist to conclude that the spirits examined are authentic or falsified. Finally, the figures obtained by various chemists, even when they use similar methods of analysis, often show only a very relative concordance.

[This speaks of the wet chemistry era before the advent of chromatography. What is interesting is that GCMS outside of single malt scotch, did not improve spirits. We know very little about spirits quality even though we are able to identify and quantify nearly all compounds in the sensory matrix. What then is limiting us? (I do have ideas.)]

The inadequacies of chemical analysis have been emphasized on many occasions. It should be noted, in particular, the examples cited by Gardrat and Varenne, in the “Revue Vinicole” of May 3, 1906 and March 12, 1908; by Taquet, in the “General Report made on behalf of the Extra-Parliamentary Committee on Alcohol” (Paris, 1906).

Gardrat gives, among other things, the analyzes of the same eau-de-vie made by four chemists of recognized fame: Girard, director of the municipal laboratory of Paris; Rocques, expert at the courts; Blarez, professor of chemistry at the Faculty of Medicine of Bordeaux; and Baudoin, director of the Cognac Municipal Laboratory:

[America also used a referee system where multiple chemists were asked to evaluate a sample to test a new methodology.]

It is pleasant to recall the letter which, on April 6, 1906, the President of the Syndical Central des distillateurs de France wrote to Mr. Bordas, Vice-President of the Commission of Methods of Analysis for the Application of the Law of Fraud, to report a good rum recognized by the Municipal Laboratory, with 637.8 non-alcohol coefficient, and which was nothing more than a mixture made before a bailiff, with a legal statement, of 34% of natural rum, water, industrial alcohol and dummy impurities of German origin (L. Jacquet) (1).

(1) L’alcool, p. 277, Paris, 1913.

In fact, “tasting and chemical analysis are two means of investigation, which have clearly different fields of action, although in contact with certain points; if they complement one another very happily, they can not replace each other and must be used simultaneously “(Mathieu).

[Advice we should no doubt heed today.]

Rum appraisal

Non-alcohol coefficient.

This coefficient was, at one time, considered as giving the measure of the quality of the rum.

Simon, for example, reported in 1909 that, according to information received from France, Martinique rums were classified into three types as follows:

The author, having carried out the analysis of 40 authentic samples from Martinique, maintained the above classification for molasses rums destined for export, but indicated quite considerable margins of variation in the rate of impurities:

As for rums of syrup, cooked vesou and raw vesou, the average non-alcohol content was respectively 332, 348 and 295.

Simon pointed out, moreover, that this method of grading had the serious disadvantage of giving too much importance to impurities which play a questionable role in the aroma. “This is how,” he writes, “it results from often repeated experiments that at the doses at which it can be found in rum, the influence of furfurol is quite negligible. The role of aldehydes is also very small when dealing with samples rich in ethers and higher alcohols.”

“Higher alcohols which can be found in large quantities in rums have an influence on the value of the impurity coefficient which is far from being in proportion to their utility. As far as harmfulness is concerned, it is to be hoped that rums contain as few as possible of higher alcohols. Moreover, their predominance gives an unpleasant flavor known as the “boiler taste”. Regarding the acidity, it would be better to assign a more important role to volatile acidity, the only one that counts in the immediate aroma… In our opinion, the most important factor of the aroma is represented by ethers. It would be desirable to take as a basis for the chemical appreciation of the aroma, a sum into which would enter, not as now the gross weights of the different groups of impurities, but these weights multiplied by coefficients in relation to the importance of the role played by the group”.

[There are lots of papers on this topic trying to arrive at these coefficients, but they are vary tedious to read and overlook a lot. Arroyo advanced the discussion creating a ratio between ethyl acetate and the other higher value esters. I often denote noble volatile acidity which does not include acetic acid.]

Jonsher (1914), who also attaches great importance to the non-alcohol coefficient in rum evaluation, proposed for establishment of this coefficient, to include aldehydes, furfurol and esters with their weights found in analysis, but to carry respectively the acids (1) and the higher alcohols, whose predominance can give the spirits an unpleasant taste for the value of only 75. The differences, in plus or minus, noted for each of these two groups, would intervene as a complement of appraisal. Under these conditions, the author considers as belonging to the superior type the rums measuring more than 550 impurities and to the inferior type those having a non-alcohol content below this figure.

(1) A high dose of acetic acid especially corresponds to an alteration of musts by acetification and can make non-merchantable eau-de-vie.

It is now admitted that the non-alcohol coefficient can only constitute an element of appraisal of very limited interest. The aroma of rum is formed by the association of many constituents of very unequal importance, of which some of the most important rum oils are not even detectable by the methods of ordinary chemical analysis. At most, it can be said that aromatic intensity is related, although there is no absolute correlation, with the non-alcohol content and the latter must not fall below a certain limit. Nor does this coefficient make it possible to effectively prove the authenticity of rums, or to detect falsifications or cuts with neutral alcohol. In France, where the repression of frauds on spirits was the subject of the legislator’s concerns, more probably than in any other country, a Circular of the Minister of Agriculture dated August 30, 1908 fixed as follows the bases of chemical appraisal:

But it soon became clear that the minimums above (350 and 450) were too high. A thorough survey of the composition of rums from the French colonies in 1913 led Bonis to conclude that the “minimum of 250 gr of impurities per hl of alcohol at 100° should be considered as the lowest that can be reached for merchantable rums, both of molasses and vesou”. The variations of the impurity coefficient also had a large amplitude:

In the Circular of March 20th, 1913, the minimum coefficients were lowered to 300 for molasses rums and to 200 for those of vesou. These figures, already very low, were subsequently reduced to 150 (Circular of February 15, 1925), under the condition that the product present at the tasting the organoleptic character of rum. It is obvious that such a minimum, motivated by the low non-alcohol of certain rums obtained by pure fermentation in the presence of antiseptics (Guadeloupe), deprives the chemist of any means of serious control. The fraudster has great latitude to cut rums containing a high proportion of impurities with neutral alcohol and to present the products of the dilution as rums with a low non-alcohol coefficient.

[I’m less shocked about the fraud and more shocked that antiseptics were a trend in Guadalupe.]

Variations of the same order of magnitude as above are found elsewhere in the rums of the English colonies. The report of the Royal Commission on Whiskey and Other Drinking Spirits (1908) indicates for rums from Jamaica, for example:

Balance of impurities.

The equilibrium existing between various elements of non-alcohol plays an incontestable role in the constitution of the aroma. For the appraisal of quality and control of rum authenticity, the Esters : Acides ratio and Esters: Higher Alcohols ratio were chosen.

Bonis, after having analyzed nine rums of molasses from Martinique, submitted them to the analysis of expert tasters, who adopted the following classification:

With exception of sample No. 6, whose anomaly can be explained by several reasons (low level of esters, higher alcohol content), the Esters : Volatile acids ratio is even lower as the rum is of better quality. “Neither the non-alcohol coefficient, nor the various constituents, taken alone”, writes Bonis, “can serve as a basis for a classification in order of marketability. It does not seem to be the same with regard to the Esters: Volatile acids report.”

[I need a reminder to revisit this data. This supports my theory that noble volatile acidity is important to the quality of rum. A rum should not have far more esters than it does noble acids.]

The various studies carried out on the molasses rums of Martinique by Simon, Bonis and Rocques tended to show that the ratio Esters: Acides rose as the non-alcohol coefficient increased. Less than 1 below 600 gr of impurities, it was greater than unity for a non-alcohol coefficient exceeding 600 (Rocques, 1913). Later analyzes, however, did not confirm this conclusion. “For molasses rums we studied,” says Zizine, “it varies from 2.5 to 0.3 (as 8 is to 1), and for rums of vesou from 4.02 to 0.3 (as 12.5 is to 1). There is, moreover, no correlation between the variations of this ratio and that of the non-alcohol coefficient. It is also important to remember that the Esters : Acids ratio undergoes significant variations during the aging of spirits, with a tendency to diminish gradually.

[If the ratio diminishes gradually that means either the spirit picks up acidity from the barrel or esters break apart and releasing acids. This supports my theory that we may use temporary “place-holder” esters to increase the volatility of the acids and move them into the spirits where they will be released from esters later.]

As for the ratio of Esters : Higher alcohols, it was also considered formerly as increasing with the coefficient of impurities. “Below 40°, “Rocques wrote in 1913, “this ratio is less than unity; from the coefficient 500, it rises much above unity.” At the same time, however, Zizine reached quite different conclusions. “For the rums of vesou”, he said, “the ratio Ethers : Higher Homologues is always less than unity. But for molasses rum, this ratio is sometimes higher, sometimes lower than 1, with a tendency to be less than 1 for molasses rums of low non-alcohol coefficient. It varies by the way, for these last rums, within such wide limits, 35.2 to 0.16, that is, 200 is 1, that it cannot represent anything very constant. No more for the rums of vesou than for molasses rum, is there is a correlation between variations of the non-alcohol content and that of the ratio Ethers: higher homologs”. And the author quotes, among others, the following examples (molasses rums):

[Here Kervegant quotes Zizine using the term higher homologue, but I think he simply means higher alcohol.]

It must be remembered, however, that in general, rums of molasses with a high degree of impurity almost always have an Esters : Higher Alc. ratio greater than unity. This is particularly the case for Jamaican and Martinique grand arôme rums. When it is in the presence of a low level of non-alcohol and a ratio Esters: Higher Alc. greater than> 1, the chemist will be able to almost conclusively conclude a full-bodied molasses rum blend cut with neutral alcohol.

[This is the current style of many of the lamer Jamaican bottlings.]

As Bonis pointed out, the ratio of Esters : Higher Alc. seems to be closely related to the nature of fermentation. “If vesou rums have a predominance of higher alcohols over ethers, it is that the fermentation of the vesou is almost always practiced normal and rapid, due to the cane yeast itself of the genus Saccharomyces. Molasses, on the contrary, will sometimes give a predominance of the higher alcohols over ethers, if the fermentation has been conducted scientifically, that is, if the previously sterilized must were seeded with a fairly pure starter, and then sometimes a predominance of ethers, which may be accentuated, if the fermentation was spontaneous and slow and if the yeasts of the genus Schizosaccharomyces played the main role.

[Bonis is acknowledging that a Pombe yeast can give a much higher ratio of Esters to higher alcohols than pure yeast molasses fermentation. There may be a two fold reason. Fission yeasts on average are known to be low producers of higher alcohols and their ferments are also known to be conducted in ways that support ester formation.]

Lusson (1) thought that one could rely on the sum of Ester’s + higher alcohols, to appraise the purity of an eau-de-vie, and on the coefficient of oxidation (proportion of acids and aldehydes contained in 100 parts of non-alcohol), to judge its maturation.

(1) Mon. Sc. Quesneville XLVII, 785, 1888.

It has indeed been observed that if the esters and higher alcohols, taken separately, undergo from one brandy to another, large variations, these are much lessened if we consider the sum of these two elements. Samples with a low ester content usually have many higher alcohols. Also, the sum of Esters + higher alcohols is an interesting element of appraisal, which the analyst can take advantage of in some cases (Rocques).

[This is fascinating advance. Kervegant is kind of saying the metabolism of the yeasts are kind of going in one direction or the other likely because of some variable that is not constant.]

As for the oxidation coefficient, it gradually increases during aging, albeit in an increasingly slow manner, and consequently provides useful indications on the age of the eaux-de-vie. However, it is hardly possible to compare products of the same origin, the acid content of young eaux-de-vie being very variable according to fermentation and distillation methods.

[So you could likely use the data to predict the age of your own spirits (which you already known because you documented it), but not another rando from someone else.]

Ester level.

Esters are generally given a preponderant share in the constitution of the aroma of rums, and in commercial transactions relating to grand arôme rum products, the rate of esters is often used to estimate the value of the product.

Allan (1906) writes about rums from Jamaica: “If we consider in a general way the rums produced in the island, grouped by parish, we can observe that parishes renowned for the high prices of their rums are easily classified according to the quantity of esters of the products. Trelawny comes first and Westmoreland second. High ester rums are not confined to a particular parish, but, without exception, when a rum contains more than 1000 esters it invariably has a high price on the market. The obvious conclusion is that a high level of esters is an essential feature of rum prices. It does not follow that the quantity of esters alone determines the value of the product: the equilibrium existing between the various esters is also a very important factor.

[You cannot cheat by having nothing more than ordinary ethyl acetate…]

“Higher alcohols, furfurol, and aldehydes, though present, are so small that they can not greatly influence the aroma. However, they can intervene, for a small part in what is called in a vague way the “body”. There is no doubt that the quality of Jamaican rum is largely due to a high level of esters if these are well balanced, the higher the amount of esters, the more valuable the rum. The experiment done on a property, whose rum was raised by 3 s. 6 d., to 7 s. 6 d. per gallon by simply increasing the rate of esters (from 344.9 to 510.4) provides conclusive evidence to support this view.

[Keep in mind, esters under the Jamaican process may be highly correlated to rum oil formation. Esters may also rely on rum oil to be valorized by the radiance concept accepted in perfumology.]

Ashby and Cousins attribute a high importance to high molecular weight esters, although the proportion is small (0.5 to 0.75% of total esters). “It has been found,” writes Ashby, “that the acetic ester forms about 98% of rum esters, but that it does not intervene much in the bouquet, and because of its volatility it is very fleeting. Butyric ester plays a more important role, but it is considered that it is to the esters of higher acids (caprylic, capric and lauric) that we must attribute a very special importance, with regard to both the body and characteristic bouquet”.

According to Cousins, ethyl acetate and butyrate only act as “vehicles” to transport high molecular weight esters in contact with the nasal mucosa, whose aromatic intensity is so extensive that they completely dominate all other constituents. “It is,” he says, “those heavy esters that exist only in trace amounts, that depend on the specific quality and practically the commercial value of the high-flavored rum.”

[“Vehicles” may still be an apt metaphor but it may work at a perceptual rather than physical level.]

Arroyo also drew attention to high molecular weight and high boiling esters passing through the 5°, 6°, 7° and 8° fractions of fractional distillation with the birectifier. The author considers that rum quality improves when the quotient of high-boiling esters and aldehydes relative to low-boiling esters and aldehydes (in the first 4 fractions) approaches unity.

Wüstenfeld and Luckow found that the force, or vinosity, of rums, determined by the dilution method, was in general proportional to their ester content. They obtained the following results in the examination of 85 rums, of which 79 were from the Jamaica:

There are, however, some fairly frequent exceptions. Thus, a rum with 1399 esters was classified in category 2, and samples with 848, 795, 709 and even 611 esters in category 5. The authors explain these anomalies by the predominance, in some rums, of esters, such as ethyl acetate, which, because of their low aroma, do not contribute much to the increase in vinosity.

Wüstnfeld and Luckow also noted that rums with a high ester content are not normally graded for tasting as top quality products, because they have an aroma that is too violent, which masks smells and flavors more fine and more pleasant. To detect these, they advise to carry out the grog test.

What has previously been said shows all the interest in the appraisal of rums by chemical analysis methods allowing differentiation of esters. It is necessary to remember especially, with that of the fractional distillation, Lebbin’s method for the determination of phenylacetic esters, and especially the methods of Grossfeld and Miermeister, for the determination of lauric acid and caprylic acid.

[Something here is a little sloppy in translation. I think Kervegant is reminding us of methods and discussion from previous chapters. Search for those authors and you will find…]

The ratio of free formic acid: esterified formic acid, proposed by Fincke, can also give useful indications as to the purity of the product. Fincke obtained with authentic Jamaican rums, rums diluted with neutral alcohol and imitation rums, the following results (that of soda 0.1 N per 100 gr of alcohol):

All authors do not give priority to esters, in the constitution of the bouquet of rums. Some (Greg, Micko, Arroyo) give more importance to the presence of an aromatic substance of the terpenes group, the essential oil of rum. Unfortunately, we do not currently have an analytical method for the determination of this substance, the chemical nature of which is poorly known. By the method of fractional distillation, however, it is possible to get an idea of the greater or lesser proportion of this aromatic component.

It also appears that high molecular weight esters play a much less important role in light, low-impurity rums than in grand arôme products. The base of the bouquet of Jamaican rum for local consumption, for example, would consist, according to Cousins, of ethyl acetate.

Higher alcohols, dry extract.

The role of higher alcohols in the constitution of bouquets is poorly known. It has been found, however, that if they fall below a certain number, the quality of various eaux-de-vie (whiskey, kirsch) is diminished.

Some authors admit that the content of higher alcohols, which depends greatly on the richness of amino acids and hardly changes during the aging of spirits, is one of the surest elements for judging the authenticity of eau-de-vie (Buttner). This is so at least in the case of grape and fruit eau-de-vie, obtained from musts having a relatively constant composition. For rums, made by extremely variable methods, from more or less rich in amino acids, with or without the addition of sulphate of ammonia, the higher alcohol content varies within a wide range. The origin and method of preparation of the product being known, the figure can however provide interesting indications.

Arroyo, on the other hand, considers that in the case of rum, a high level of higher alcohols is unfavorable and that the fineness of the product increases when the proportion of the fusel-oil with respect to the non-alcohol coefficient is low.

The determination of the nature of higher alcohols, using for example the method advocated by Penniman, Smith and Lawshé, with different aldehyde reagents, also makes it possible to be aware, in certain cases, of the type of rum and to distinguish in particular the  grand arôme rum products where normal butyl alcohol predominates, ordinary rums, being dominated by amyl and isobutyl alcohols.

Finally, the analysis of the dry extract provides information on the treatment that rums have undergone after production: aging in barrels, addition of sauces, etc. It often gives much greater precision than the determination of volatile products relative to the origin of the products (Quantin, Valaer).


Actual tasting, gives interesting results especially when it is practiced by trained people having experience types for comparison, usually distinguishes, much better than chemical analysis, real rum from artificial rum, old rum from the young product or artificially aged, rums of molasses from those of vesou and finally the rums of different origins (Martinique, Jamaica, Demerara, Cuba, etc).

Natural rum, even of mediocre quality, has a developed bouquet, frank and persistent, a soft and not burning flavor. It is usually easy to differentiate from artificial rum. The industrial alcohol used in the composition of the latter, has a burning flavor, which dries the palate and leaves an unpleasant impression. At the same time, the bouquet is generally accentuated, coarse and always fleeting, when obtained by the addition of essences and sauces, never has the properties of a natural rum aroma which has not yet been artificially reproduced so far. With a little habit, we can also detect mixtures of natural rum and neutral alcohol, where we find the weakened aroma of rum and the burning flavor of industrial alcohol.

Young rums, especially those of molasses, are distinguished by their more or less coarse bouquet, lacking mellowness and integration. Old rum has a finer aroma, though powerful and persistent, it leaves a sweet impression on the palate, devoid of drought, warm and agreeable. Artificially aged products are usually recognized by their lack of body, due to the fact that the alcoholic degree has to be lowered by the addition of water. The presence of caramel is easy to detect, for an informed taster, by the special sweet taste that it communicates with the eau-de-vie.

The bouquet of molasses rum is very different from that of vesou rum and no taster can be wrong in this respect (unless it is a strongly rectified product). The characteristic aromas are still apparent in the mixtures of these two types of spirits, even in rums obtained from musts consisting of a mixture of undefected cane juice and molasses. Finally, despite the diversity of brands, rums from the different producing countries generally have sufficiently distinct characteristics so that one can, by organoleptic examination, specify their origin and even sometimes indicate their presence in significant proportions in blends.

[I feel like this last point is less and less true as consultants have created fads homogenizing technique and internationally available yeasts have homogenized production. For molasses rums, a renaissance of pombe yeasts would create a return to distinctive styles of rum.]

With regard to the quality ranking and the determination of the commercial value, tasting obviously provides much clearer and more precise indications than chemical analysis. Some abnormal tastes (boiler taste, pungent taste, etc.), which the chemist is often powerless to detect, will be easily perceived at the tasting.

Organoleptic examination of the different fractions of fractional distillation (Micko’s method) will make it possible to differentiate in a much clearer way the different aromatic substances entering into the constitution of the bouquet, and consequently to obtain more precise conclusions with regard to the origin, purity and quality of the product. Finally, by the determination of vinosity using the method of successive dilutions, it will be possible to translate aromatic stewardship into figures and to reduce appreciably the subjective character of the assessment, which constitutes the essential defect of organoleptic analysis.

[I think he means stewardship sort of like wine stewardship.]

Repression of frauds.

From what has just been said, it follows that chemical analysis makes it difficult, as a result of the variability of rum, to conclude that any spirits are diluted or falsified. It has been proposed, on a number of occasions, to fix minimum non-alcohol coefficients.

Thus Sanarens, in 1925, suggested the following standards for the rums of the French colonies:

In Jamaica, in 1905, it was proposed to prohibit the export of products with an ester content of less than 200, but this proposal had no follow-up. On the other hand, in 1934, the maximum number of esters that could be contained in the rums of this colony was fixed at 1,600.

In Venezuela, cane eau-de-vie, as well as other alcohols, must not have a non-alcohol coefficient greater than 350.5, with the following maximum for each group of impurities (in mgr. p. 100 cc of pure alcohol):

The application of such standards leads to the elimination of extreme types, which can only be done to the detriment of certain producers; or the standardization of types by the blending of rums between them starting from the colony, which also presents difficulties of realization.

[My theory of some of the beloved Ron Zacapas was that they had stocks that were very old but had to aged character, so to make them taste like expectations of their age, they bought grand arôme stocks from elsewhere. They were extremely successful selling these but do to making factors and attention, they were unable to keep supplying the same blend. Similarly, the pot still part that makes Ron de Barrilito so beloved comes from an unnamed distillery in the Dominican Republic. I also do not believe there is any fraud in any of the two blends I just mentioned. Eventually to handle these complex story lines we will move to the language of “hosting” and “access” to heavy pot still grand arôme rums.]

Organoleptic examination gives safer indications as to the differentiation between real rums and imitation products. But the conclusions which it provides, of a largely subjective nature and which can not be translated into indisputable figures, do not generally constitute a sufficient legal basis for the conviction of the fraudsters by the courts.

Practically, the agents of the Fraud Control have been able, in France, to obtain convictions with regard to the fraudsters only in very rare cases. So we have arrived at the conception of an accounting control.

Rum circulating under the control of the Régie, the accounting basis existed in principle: it was sufficient to examine the accounts of a wholesaler on the filings of the régie, to be aware of the inputs and outputs. If the latter proved more important than the entries, it was obvious that the merchant had defrauded. Unfortunately, the Régie accepted that the movement titles accompanying the rums indistinctly bear the mention of rum or various spirits. This did not damage the rights of the tax authorities, for whom only the entire amount of pure alcohol circulating was imported, but it made the task of the Fraud inspectors very difficult, obliged to count the debits and credits called various spirits and to look for those who, in reality, accompanied the goods sold under the name of rum.

[They they are paying all their taxes, but they are defrauding the name rum which must be protected to defend the industry which relies on positive consumer sentiment and trust.]

To simplify the work of control, it was necessary to establish a rum account, similar to that of the appellation of origin instituted by the law of May 8th, 1919, to protect crû wines. This account was created by the Finance Act of April 16, 1930. It states in Article 43 that “the entries and exits of rum (quantities and degrees) will be mentioned in a special column, distinct from other spirits, whose control will be subject to all requisitions to agents of indirect contributions and the repression of fraud, which check the accuracy of this account and those existing in stores.”

Thanks to this legislation, the suppression of fraud is considerably facilitated. It can be done by simply collecting invoices and reconciling the accounts of merchants senders and receivers.

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