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PREPARATION OF RHUMS FOR SALE
The eaux-de-vie, before being delivered for consumption, are generally subjected to a series of operations intended to lower their alcoholic strength to around 45 – 50° (reduction), to mix them together in order to have a product of regular quality (cutting), to give them the desired color, to improve the taste and the bouquet (bouquetage, sugaring) and to clarify them (filtration, collage).
The rum is sometimes delivered for colorless consumption (grappe blanche of the French West Indies, clairin of Haiti, ron carta blanca of Cuba and Puerto Rico) or slightly tinted (carta de oro of Cuba, etc). As a rule, however, this spirit is strongly colored. The intensity of the color varies, moreover, within wide limits; from less than 10 to more than 40 degrees Lovibond brewing scale, brown series, using for the examination a half-inch cell. Some rums from Jamaica and Demerara mark up to 70° Lovibond.
The color can come only from the extractive materials ceded by the wood of the barrels (tannin) or “sauces” made of prunes, tar, etc., added to the rum. Most often, however, it is due, at least in part, to the addition of caramel.
Coloring by wood and caramel has been used for a long time in rhummeries. Ducæurjoly wrote in the early nineteenth century.
“The following ingredients can be used for the same purpose: Take the raw sugar found in the bottom of a barrel, which is usually not purged to dryness, boiled in a container, at the consistency of a large thick syrup: it is allowed to cool; this matter becomes very brittle, it is dissolved in a certain quantity of rum, and the result is a liquor of which one glass is sufficient to color 100 gallons of rum.”
“There are still many other methods of coloring the rum, but the simplest, and the least inconvenient, is to have the cooper burn the internal walls of the staves intended for barrels that must contain this liquor, in a few days it takes a beautiful amber color that appeals to buyers.”
Caramel is obtained by heating sucrose or glucose at about 170 – 190°, for 3 – 4 hours. Gelis (1), as a result of his work on the substances which originated by subjecting sugars to the action of heat, had been led to admit that the caramel consisted of a mixture of three products: caramélane, caramélène and caraméline.
(1) Ann. Chim. Phys. (3), LII, 352, 1858 : LXV, 496, 1862.
The caramélane is separated from the crude caramel by treatment with 84% alcohol, caramélène by treating the residue of the previous extraction with water. The remaining product, of a colloidal nature, is caraméline. These substances correspond to different degrees of dehydration of sucrose: when the loss of weight is 10%, we obtain mainly caramélane; when it is 14 – 15% of the caramélène and when it reaches 20 – 25% of the caraméline.
The caramel also contains a bitter substance, which is found in all the products of heat decomposition of carbohydrates and which Reichenbach (1) designated as assamar. Finally, when the caramelization takes place in the presence of soda, potash or lime, it forms a brown matter, slightly soluble in alcohol, almost insoluble in water, insoluble in ether, carbon sulphide and other organic solvents, but easily soluble in alkalis, to which Schweizer (2) given the name of alcaramel.
(1) Liebig’s Ann. Chem. XLIX, 3.
(2) Z. Deut. Ges. Brauw. (4), XXIII. 46. 1900.
Recent work by A. Schweitzer (3) has shown that caramélane, caramélène and caraméline, the existence of which as definite chemical compounds have been accepted for a long time, are actually constituted by mixtures, in variable proportions, isosaccharosane and humin.
(3) Ree. Trav. Chim. Pays-Bas LVII, 345, 1938.
Isosaccharosane, isolated by Pictet in 1924, is the first product of sucrose dehydration. It has the formula C12H20O10. It is a colorless, amorphous substance, melting at 94°, soluble in water and methyl alcohol, insoluble in ether and acetone. Humin, which has been assigned the formula (C24H20O9)n, is a highly dehydrated and highly polymerizable carbohydrate of a colloidal nature and dark brown in color. Insoluble in water and ordinary solvents, it goes into colloidal suspension in the presence of isosaccharosane, which prevents its flocculation.
The greater the dehydration of sugar, the higher the proportion of humin and the lower the solubility of the caramel obtained. The coloring power of the caramel increases with dehydration. When the caramel is prepared from glucose or levulose, instead of isosaccharosane, glucosane or levulosan, colorless and amorphous materials form, of formula C6H10O5-, which play the same role as isosaccharosane in the dispersion of humina.
Von Elbe (4) has arrived at similar conclusions. According to this author, the caramel is constituted by the mixture of two amorphous and colorless compounds, very close to sucrose, and a dark brown humic material, presenting the properties of a lyophilic colloid. The latter is maintained in the state of suspension by the former; separated from them, it coalesces and loses the property it previously had to give suspensions. One of the colorless substances is bitter and slightly burning, very hygroscopic, soluble in pyridine, acetic acid, methyl alcohol, poorly soluble in absolute ethyl alcohol and acetone; It reduces Fehling’s liquor and decomposes at 95° with release of odorous products. The other has a sweetish flavor; it is less soluble than the preceding one, reduces Fehling’s liquor and decomposes above 140°.
(4) J. Am. Chem. Soc, LVIII, 600, 1936.
In the presence of humic matter, the physical properties of the other two substances are modified: the thermal stability and the resistance to solubilization are sharp. As the caramelization progresses, the molecular weight increases, the solubility of the mixture decreases. If the heating is prolonged until a hard and brittle mass is obtained which does not release more gas, the product formed is insoluble in cold water and organic solvents. It contains approximately 25% humic matter, 43% bitter colorless matter and 23% colorless sweetened matter. The curing stage is reached when the saccharose weight loss is about 20%.
The caramel of trade is generally in the form of a thick liquid, viscous, blackish brown, sometimes with a slightly bitter flavor. Prepared in the presence of alkalis, it has a special flavor and smell. Its density is between 1.030 and 1.040. Its staining power is very variable: evaluated using the Lovibond colorimeter, by examining an aqueous solution of caramel at 0.1% in a 1 inch cell and with the series of glasses No. 52, it usually varies between 15° and 30°, but it can reach up to 60°.
A well-prepared caramel must not ferment and therefore not contain undecomposed sugar. This can be seen by subjecting it to a fermentation test with yeast or by determining the reducing power with respect to the Fehling liquor. This reducing power also varies within wide limits with the caramel composition: it can be between 0.3 and 1.6 of that of glucose taken as a unit (N. Deerr).
According to Fetzer (1), the pH of a caramel is a good indicator of the quality of it. When it is less than 6.0, the product may rot. High pH also indicates incomplete sugar processing or the presence of excessive alkali. When, on the contrary, the pH is less than 2.5, the caramel resinifies.
(1) Ind. Eng. Chem X, 349, 1938.
The viscosity has a certain importance. If it is excessive, it indicates that the sugar has been cooked too much. Normally ashes are not related to quality. However, when their level exceeds 3%, they can influence the flavor of the treated liquid. The iron content sometimes reaches a high percentage, as a result of the use of mild steel pans for the preparation.
Depending on the intended use, the caramel must have different properties. Thus, when destined for the coloring of vinegar or beer, it is important that it can resist the action of weak acids, without losing its coloring intensity and especially without forming a deposit. When used for the coloring of spirits, it must not create a louche if the alcoholic strength reaches 70 and even 80°. At the same time, it is important that the apparent degree (obscuration) be kept as low as possible, since commercial transactions are always made according to the latter. Finally, it must give the product, especially when it comes to rum, a slightly sweet flavor. These last two properties are antagonistic: to have a sweet flavor, the caramel should not be overly cooked, but then the coloring power is low and darkening more important.
Caramel prepared with pure sucrose is only weakly retained by the carbon. The bleaching action of it is negligible compared to that of certain metal compounds (lead and aluminum salts in particular). The caramel is precipitated from its solution in ethyl alcohol by amyl alcohol, as well as by the acetate of ammoniacal lead. [This information is important for government agencies like the TTB who determine if a spirit is beyond the permissible level of caramel.]
The caramels are made from cane sugar, glucose or molasses. The properties of the products obtained are about the same, regardless of the raw material used. However sucrose caramel is always more bitter than that of glucose (Salamon and Goldie). It is generally prepared as follows in the West Indies:
In a large basin of iron placed on a masonry hearth, sugar is introduced with about half of its weight of water, so as to have, after dissolution, a density of 1.25. Heat, first gently and more strongly afterwards, skimming carefully at the beginning and stirring the mixture constantly, with a wooden spatula or better a mechanical stirrer, to prevent the sugar from sticking to the bottom of the container and burning. The sugar melts at first, then becomes more and more colored, spreading abundant ecstatic and irritating vapors. When the cooking is complete, the fire is stopped and warm water is gradually added, stirring vigorously to dissolve the caramel and bring it to the desired consistency. The product is deposited for a few weeks in wooden vats. It is then withdrawn and a little alcohol (10% for example) is added, before sending it to special barrels, where it is allowed to rest for a while. The product improves with storage. Sugar gives approximately its weight in caramel.
It takes experience to know exactly when to stop cooking. One can, to test it, plunge a stick in the mass and after cooling crush with the fingers the caramel: it must be very brittle. You can also drop a drop of caramel in water: if the drop floats, cooking is sufficiently advanced. These tests are applied in English Guiana in the preparation of the caramel used for the coloring of rum if one wants to obtain a product with higher coloring power, giving a low obscuration, one pursues the cooking a little beyond, until the point where a stick, if immersed in the mass and strongly withdrawn, the adhering caramel solidifies without flowing (N. Deerr).
[It appears its an art to have caramel for coloring that is dark, while not effecting obscuration and increasing sweetness. Possibly some countries bottling rums with too much sugar were somewhat bad at preparing caramel and ended up finding consumer acceptance.]
Treating the caramel with strong alcohol increases the coloring power and decreases the obscuration. N Deerr advises mixing it with its volume of alcohol at 90-95° and let it drop. The clear decanted part makes it possible to obtain a very dark coloration of the rum, with a slight loss of apparent degree. [I’m not sure which part you keep, but I bet that becomes apparent when you perform it.]
The caramel obtained by the process of manufacture described above is suitable for rums grading 60-65°, which are produced in French colonies. But for rums with higher degrees (80-85 °), it gives an abundant precipitate, which is redissolved easily if one reduces the alcoholic degree. The cooking of the sugar in the presence of an alkali makes it possible to avoid this disorder.
In the Asrymusry process, used frequently in the West Indies and French Guiana according to N. Deerr, 60 kilograms of sugar are added and before starting the heating, 2 kilograms of Na or K carbonate or 1.5 kilograms soda or caustic potash, previously dissolved in a double weight of water. When the caramel is intended for the coloring of vinegar and beer, the soda is replaced by carbonate of Am, with the dose of 3 kgs for 60 kgs of sugar. This last product does not dissolve in alcohol without disturbing it, just as rum caramel determines a disorder in vinegar.
Pairault was able to produce a product giving satisfactory results for the coloration of high-proof rum, by heating by the usual process a mixture of 125 kilograms of sugar, 23 liters of limestone water and 35 liters of ordinary water.
In the Mc Cowan process (1898), glucose, mixed with 5 to 10% ammonia liquor (density 0.880), is heated in a closed container at 100° for 24 hours. The mixture is then brought to the proper concentration.
Wheeler (1910) proposed to operate as follows: add 7.5% ammonia solution to glucose (0.880 density) and bring the temperature to about 119° C for 30 minutes; then cool to 107°, add 4% ammonia again; finally heat to 119° for 10 minutes.
Salamon and Goldie (1) found that the addition of salts of soda and potash, of ammoniacal salts, of mineral or organic acids, to the sugar, greatly increased the coloring power of the caramel, but it also often had disadvantages. Mineral acids, even in small quantities, have a brutal action and can cause the carbonization of sugar. The effect of acetic acid on the coloring power is rather uncertain; on the other hand, the caramel obtained has a pleasant taste and remains brilliant in the beer.
(1) J. Soc. Chem. Ind. XIX, 301, 1900.
With tartaric acid, the coloring is good, but the flavor is harsh and hard.
The salts of potash and soda increase the coloring power; but, if they are used in large quantities, the caramel takes a very unpleasant soapy taste and secondly, it causes a disorder in the beer. These disadvantages, however, would be reduced by adding alkaline lye only when the caramelization is substantially complete.
The ammoniacal salts give better results than those of potash and soda, at least as regards the coloring of beer and vinegar. If the carbonate has an uncertain action, the acetate of Am makes it possible to obtain a caramel of beautiful coloring, pleasant flavor, not disturbing the beer. The product prepared with Am sulfate gives the beer a nice color and shine, but the flavor is very harsh. Am chloride has a similar action; however, the coloring power is lower and the flavor less harsh. The doses giving the best results would be per 100 kilograms of glucose: for Am carbonate 1 kg; for chloride, sulphate and acetate of Am 15 kg: for tartrate of Am 2.5 kg; for Na carbonate 1 kg (Salamon and Goldie).
According to Herzfeld (1), if one wants to obtain from sucrose a good caramel, with a high coloring potential, which does not cause a haze in alcohol at 80%, or in beer, it is first necessary to carry out the inversion of the sugar, and then eliminate the acids which are born during the caramelization, either by raising the temperature to 180-190°, or better by neutralizing them by means of ammonia. The author, by slowly heating an invert sugar syrup at 80% in a glass boiling flask placed in an oil bath, and once the boiling is obtained, by letting drops of ammonia drop by drop as the water evaporates gradually, and finally raising the temperature to 170-180°, was able to obtain an almost tasteless caramel, with a coloring double that of the best commercial caramel, dissolving without disturbing both 80° alcohol and beer and vinegar. The solution did not cloud at low temperature (-8° C), did not lose its intensity by treatment with acetic acid and did not give a precipitate with lead acetate.
(1) Deut. Zuckerind. XXXV, 617, 1910.
[I think the caramel’s used today can achieve these targets.]
Molasses is often used for the preparation of caramel. This is particularly the case in English Guiana, where one operates according to the process indicated above for the manufacture of caramel in the West Indies, after having simply diluted the molasses with water, so as to have a density of 1.25. As the mass tends to foam during heating, it is advantageous to add a few drops of a fatty substance or wax pellets.
For the coloring of rum in the countries of origin, sugar caramel or cane molasses are used. In Europe, for spirits, it is preferable to use caramel pure sucrose, and for the common brandies caramel of glucose or molasses.
Coloring must be done before reduction. In the rum producing countries, it is usually carried out right out of the still. The rum is usually left for 3-4 days, after which it is put in barrels. If the alcohol is dirty, it is advisable to carry out a filtration or a racking. Alum, at the dose of 25 gr per 100 liters of brandy, gives good results.
[The racking would involve the fining with alum and then pouring off the clear distillate.]
The amount of caramel to be added obviously varies with the final color to be acquired, which depends on the nature of the brandy and the requirements of the consumer market. Generally rums are much more strongly colored than other spirits. Those of Demerara have a particularly dark hue. An average dose is 4-5 liters of caramel per 1,000 liters of rum, but sometimes up to 10 liters are used. The reduction in the apparent density resulting from the addition of caramel can vary from 0°5 to 1°5 G. L.
[That reduction is obscuration of the true ABV by the caramel.]
Various dyes of mineral origin are commercially available. Their employment, condemned elsewhere in most countries by the laws on the repression of frauds, is never advisable. If they make it possible to obtain a very weak obscuration, they spoil the flavor and the bouquet of the eaux-de-vie, and the coloration which they determine is not stable.
Consumption eaux-de-vies generally measure 40 to 50°. The alcoholic richness of rums delivered for sale varies most often in France from 40 to 45°, but it sometimes goes down to 35°. In the United States, it is a little higher: 42 to 50°. In the French West Indies, the measure reaches 55° (rum called reduced) and sometimes 65° (rum not reduced). As the alcoholic degree at the exit of the distillation apparatus varies, according to the countries, between 65° (French colonies) and 85° (English colonies, Cuba), it is therefore generally necessary to cut the rum with water.
This addition of water has serious drawbacks. Not only is there a decrease in the rate of secondary products which constitute the aroma of the eau-de-vie, but also the saponification of some of the esters and the precipitation of essential oils (in particular of the essence of rum) less soluble in diluted alcohol. The bouquet of the processed spirit is both weakened and unbalanced.
[I don’t know why he says “essence of rum” instead of “rum oil”. Kervegant does however note aroma breakage right off.]
The adverse influence of the dilution is more or less pronounced, according to the composition of the original eau-de-vie, the quantity and quality of the water used, the temperature and the manner in which the operation was conducted. Arroyo has observed losses ranging from 20 to 60% of the total amount of esters originally existing in rum. The saponification of the esters continues during the first months after dilution: at least for 3 months and sometimes up to 6 months. It is all the more accentuated, when the rate of the esters is higher. It is also evident that the higher the dilution ratio, the greater the changes to the eau-de-vie.
The water used for the reduction must be as pure as possible. It is generally accepted that distilled water is the best. According to Schidrowitz and Kaye (1), this would decrease much less the content of esters and acids than river water, which would cause the hydrolysis of at least 15% of the esters. Luckow (2) found, however, that distilled water did not offer any appreciable advantages over ordinary water, when the latter is pure.
(1) Analyst XXX, 149, 1905.
(2) Pharm. Zentralhalle LXXXIII, 361, 1932.
Above all, it is important that the water be free from bad taste and calcium salts, which produces a precipitate and, consequently, a louche in the presence of alcohol.
Distilled water is not always odorless, because of overheating of organic material in the boiler; but when carefully prepared, it is strictly neutral to taste. In large installations, special stills are used to obtain it. These consist mainly of a fine tin-plated copper boiler provided with a steam circulation coil. The boiler, wide and of low height, is surmounted by a very high purifying column, forming a foam breaker, which retains entrained particles in the vaporized water that can contaminate the distillate. It is continuously fed by hot water coming from the receiver, thanks to an automatic device allowing to maintain in the boiler a constant level.
Rainwater, which has been able to absorb a lot of oxygen, is very good for the cutting of eaux-de-vie, to which it communicates a certain mellowness. However, it is likely to acquire, during storage, bad odors and, if it comes from metal tanks, an unpleasant and very persistent taste. River and spring waters can also be used, provided that they are very low in mineral matter. As for the stagnant waters, whose purity generally leaves something to be desired, it is better to eliminate them systematically, if they present the slightest defect in taste.
Bad tasting waters, if there are no others options at our disposal, may be used after filtration on charcoal, and those rich in lime salts after prolonged boiling or after stirring in the presence of a milk of lime (250-300 grs per cubic meter of water), followed by filtration.
In order to minimize the saponification of the esters and the precipitation of essential oils, it is advisable to use alcoholic water (15-20% alcohol), which has been subjected to aging beforehand with oak chips, in order to carry out the dilution (see chapter X). But it is still preferable to abolish the operation of the reduction, by distilling the eau-de-vie to such a degree that after normal aging in barrels, it is reduced to the measure of consumption.
The incorporation of water should be done slowly, in small portions, and stirring the mixture after each addition. One generally operates in a barrel, when it comes to small quantities of eaux-de-vie to be treated. In large installations, a special vat, called cutting vat or mixing tank, made of oak wood is used. The tank is closed, to prevent the loss of alcohol, and equipped with a mechanical stirrer, generally consisting of two vertical shafts, whose paddles interlock and rotate in opposite directions to each other.
Arroyo advises to heat the dilution water at about 5° above the temperature of the rum to be reduced, and then to bring it into the alcohol slowly and continuously through a tube of tin or tinned copper plunging to the bottom of the tank and finished with a finely perforated watering can. Throughout the duration of the operation, the liquid is kept in slow motion, using a mechanical stirrer. The more slowly the water is incorporated into the spirits and the thinner the holes in the feed tube, the better the results.
The amount of water to be added can be determined by means of the general formula:
where a is the degree and d the density of the spirit to be diluted, A the degree and D the density of the mixture to be obtained.
The volume obtained, as a result of the contraction of the added liquid, is given by the formula:
To avoid calculations, dilution tables were established, giving in liters the amount of water to be added per hectoliter of alcohol to lower it to the desired degree.
The reduction of eaux-de-vie can be achieved either after aging, as is usually done in Europe, or before aging, following the method most often applied in the United States. This last way of doing it makes it possible to reduce the losses in alcohol during storage and avoids unbalancing the spirits at the time of release for consumption. It has the disadvantage of requiring a larger capacity of barrels, as well as delaying aging and stabilization of eaux-de-vie. In any case, if the operation is done after aging, it is important before putting the product on sale, to wait a few months where a new equilibrium is established.
It is rare for alcohol to be delivered for consumption without being blended. The different eaux-de-vie have, in fact, particular qualities recalling their origin. Some, obtained with distillatory apparatus equipped with rectifiers, are almost neutral; the others have an accented bouquet varying with the terroir; some are light, others have body, etc. It is advantageous, therefore, to correct and improve their bouquet, blending them together, so as to obtain the qualities sought by the consumer.
[I think the use of terroir here is the negative version akin to tufo.]
On the other hand, to lower the selling price of common spirits, natural eaux-de-vie are mixed with good-quality industrial alcohols (grain, beet, potato alcohols, etc.), which are cheaper.
Some rums with very pronounced aroma are particularly suitable for stretching with neutral alcohol. This is the case of the German rums of Jamaica, undrinkable as they are and which communicate with mixtures containing up to 10 times their volume of neutral alcohol the flavor and fragrance characteristics of real rum. It is also thanks to this property that these spirits could continue to enter Germany, despite the very high tariffs on imported spirits. Rums, even if they have only a moderate level of impurities, are normally very aromatic, which explains why they are the object, much more than other eaux-de-vie, of blending with neutral alcohol.
[This very last point fits the rum oil pattern. Rum a category likely has more odorants like the rose ketones related to remarkable persistence.]
Finally, blends are motivated by the need for traders to deliver for consumption a consistent product.
Bachellier writes about the rums of the French colonies: “The role of trade is not confined to a simple breakdown of the quantities purchased wholesale in production. Colonial rums are not of a uniform type. Martinique has richness in aroma, Guadeloupe brings its mellowness, Réunion is piquant. Just as a wine rich in degree is improved by a growth of lower density, but of more penetrating acidity, the same rum, perfumed and full of flavor, would lack length without the help of another type, less rich in essence but more solid, if we can say, in alcohol. And then the French clientele has its preferences or habits. What she requires above all, it is a type pleasant to the taste and especially regular… It is precisely the dealer of the metropolitan merchant that knows how to practice these assays and adapt the types to the taste of the customers”.
“Blending is a delicate operation, which can only be done properly by a trained practitioner. “The mixture of eaux-de-vie of different ages and crûs,” Baudoin writes, “is an art. One has body, another has aroma of terroir, that one has rancio, etc., and as each merchant has his favorite mixture, it follows that the formulas are kept secret.”
[I can’t quite tell if this quite is from a rum blender or a Cognac blender, but its very general anyway.]
The mixture can be made in barrels, where a suitable and predetermined proportion of each of the spirits is introduced. The addition of these must be done slowly, to avoid the saponification of the esters. The mixture is then stirred, or the drum is rolled.
In large plants, blending is carried out in glass or vitreous vats, or in wooden casks, which can be closed during the operation to avoid the loss of alcohol. A mechanical stirrer is arranged inside. Pumps and piping used for the handling of spirits must be kept in a clean state. We often use crystal cylinder pumps, to facilitate cleaning.
[Vitreous likely implies glazed ceramic. I’m not sure about a crystal cylinder pump. I may literally be made of extremely uniform glass crystal. This was pre-stainless steal and HDPE so you had to be clever to make everything inert.]
Blending can be done either before or after aging. The first method has the advantage of giving more homogeneous eaux-de-vie, mellower and more integrated.
When blending spirits of substantially different qualities, the mixture has, indeed, little uniformity in the early stages following this operation. There is a dislocation of original eaux-de-vie. The content of acids (total and volatile) and esters is generally very different (in plus or minus) from the average content calculated from the chemical composition of the constituents (Schidrowitz and Kaye). It is only with time that the “asperities” of the mixture disappear, and that it happens to form a homogeneous whole, presenting a character of its own. It is important, therefore, that the spirits be delivered for consumption only a certain time after blending.
[A synonym of asperity is ruggedness. When freshly mixed you can often tell where one thing ends and another begins. This may be a feature of cocktails that are mixed a la minute, but undesirable in a spirit.]
To hasten the standardization of the eau-de-vie, it is subjected to the tranchage operation, which we have already mentioned. The mixture is made in the conge à trancher, which has on its side side an site glass with a graduated scale, to be aware of the proportion of each product added. The different eaux-de-vie and possibly water, reduction is made at the same time, are each fed by a pipe terminating at a central distribution box, from where a single pipe exits. The apparatus being loaded, the mixture is agitated by means of a mechanical stirrer placed in the box, and the temperature is brought to 60-80° C. After the slowly cooling, the alcohol is expelled by air pressure in casks or barrels, where it is left to be filtered later.
[tranchange or trancher may best be called a diffuser where the liquid is diffused into small increments to be absorbed with less shock.]
Sometimes also, the mixture is placed in the boiler of a batch still and subjected to distillation. This is done especially when blend eau-de-vie with neutral alcohol. The latter is previously reduced to the desired degree with water.
The bouquets or sauces, are mainly used to flavor the high-proof neutral alcohols sold, after reduction to the commercial degree, under the names of artificial eaux-de-vie, imitation eau-de-vie, fantasie eau-de-vie, etc. But they are also used to increase or modify the aroma of certain natural spirits whose bouquet is not very accentuated or has a defect.
The practice of bouquetage is widely used in various rum producing areas. This is particularly so in Cuba, where rums, distilled at a high degree (80° and above), are subsequently filtered on sand or charcoal so as to eliminate the characteristic taste and odor of the natural product. A new bouquet is made by adding various ingredients to the distillate: fruit juices, wines, bay leaves, etc.
In Barbados, the spirits of cane molasses are also stripped of their “sui generis” character, by high-degree distillation (85-90°) in the presence of lime and soda or of various materials (vegetable roots, coconut husks, etc.), then flavored by the addition of foreign products (sherry, Madeira wine, bitter almonds, raisins, etc.).
In English Guiana, export rums are usually shipped as is. But those destined for local consumption is often added with aromatic products (prunes, Valencia raisins, spices, etc.). The mixture is allowed to stand for 24 hours, after which the water necessary to reduce the degree to 45°-47° is added, as well as the coloring matter. After 3 or 4 days of rest, it is usually completed with isinglass and milk, then left to age in barrels.
On the other hand, in the French Antilles and Sainte-Croix, rums are in principle never added with foreign ingredients, with the exception of caramel. It is the same in Jamaica and the regions of the United States producing rum. On their arrival on the consumer markets, they may however be the object, on behalf of importing traders, of various treatments (blending, reduction, bouquetage, etc.), with the aim either of adapting them to the taste of the customers, or more often allow their stretching with neutral alcohol.
In France, bouquetage is no longer practiced but only in a legally restricted way. It is generally limited to mixing rums of various origins between them, to reduce the alcoholic strength by addition of water and to add a little sugar syrup. Some traders use small quantities of sauces, which include tea, prunes, cinnamon, etc.
This is not the case in the United States. “Although some genuine rums,” writes Valaer, “are bottled unmodified by rectifiers, most of the products they make are blends and imitations. Manufacturers of imitation rum in the United States typically add real rum to ingredients such as: neutral alcohol, fruit juice, sugar, artificial materials and artificial colors. Rums that are distilled to a low degree and are rich in impurities are sometimes used as bases for neutral spirits and coloring matter. Other types of imitation rum are obtained, adding commercial essences to neutral alcohols and water”.
The bouquetage should be done with great care and by a skilled practitioner, so as not to spoil the quality of the eau-de-vie. The formulas of “sauces” or “bouquets” are numerous and kept secret in general by the merchants who employ them. The most varied products can be included in their composition:
(a) dried fruit (prunes, raisins, almonds, hazelnuts, juniper), fruit juices (pineapple, orange, lime, lemon) and liqueur wines (Madeira, Malaga, muscatel, muscat, sherry, etc.);
(b) tinctures or essences of spice plants: cinnamon (Cinnamomum zeylanicum Nees), vanilla (Vanilla planifolia Andrews), clove (Eugenia aromatica Baill.), wood of India (Pimenta acris Kostel), four-spice (Pimenta officinalis Berg.), nutmeg (Myristica fragrans Houtt), laurel (Laurus nobilis) Tonka beans (Dipteryx odorata Willd.);
c) infusions, tinctures or essences of various aromatic plants: sassafras (Sassafras variifolium Kuntze), sandalwood (Santalum album L.), iris of Florence (Irisi florentina L.), balm of Tolu (Myroxylon toluiferum HB.K.), balm of Peru (Myroxylon peruiferum L), areca nut (Areca Catehu L.). bitter almonds (Amygdalus communis L.), anise (Pimpinella anisum L.);
d) infusions of stimulating plants: tea, coffee.
e) tannins: oak tannin, walnut husk (Juglans regia L.), cachou (Acacia catechu Willd.);
(f) powder or extracts of pepper (Capsicum spp.), pepper (Piper nigrum L.), ginger (Zingiber officinale Roscoe), commercial alum, etc., acrid substances intended to give the eau-de-vie more “nerve” stimulating and “biting”;
g) wood tar, tanned leather, etc.
Wood tar and tanned leather seem to have been used frequently in the past. We read in the “Technological Dictionary” (Paris, 1831), in the article Rum: “To give it the amber yellow color that is known in commerce, and to communicate the particular taste that we are accustomed to find in rum, it is infused in a part of the liquid variable proportions of prunes, scraps of tanned leather, cloves, tar, etc.; the desired coloring is usually completed by adding the necessary quantity of caramel. The proportions of the ingredients which we have just named constitute what is commonly referred to as “sauces”; they vary a great deal in the different factories, and from this result the varieties of rum that connoisseurs esteem more or less because of their particular taste.”
The following sauce formulas are indicated by Basset (1):
(1) Guide théorique et pratique du fabricant d’alcools et du distillateur. Paris, 1873.
a) Take 2 kgs of grated beef leather, 300 gr. crushed oak bark, 15 gr. of cloves that are introduced into 100 l. eau-de-vie. Add the alcoholic solution of 15 – 20 gr. of softwood tar and let it macerate for a fortnight. We then filter and color with caramel.
[Remember, fortnight is the tell that Kervegant has disdain for the idea.]
(b) To macerate for one month in 10 liters of 85° brandy: 4 kgs of fresh tanned leather, 1 kg of black truffles and 25 g. of orange zest. This sauce is introduced with rum in a cask, which was previously impregnated with tar smoke.
Villon, in his “Dictionary of Industrial Chemistry”, gives the following recipes, among the most used for the improvement of eaux-de-vie:
a) Addition of an infusion of 50 gr. of green tea and 50 gr. black tea in 1 l. boiling water, per 100 l. eau-de-vie.
b) To macerate for 1 month in 1 l. of rum: 2 gr. of iris powder, 5 gr. crushed vanilla, 50 gr. sugar and zest of 2 lemons; filter. Make an infusion of 15 gr of green tea and 15 gr. of linden flowers in 1 l. of boiling water. Mix the two liquids and add them to 100 l. of brandy, with 25 gr. ammonia;
c) Mix: 2 l. old rum, 2 l. old kirch, 1 l. of sugar syrup, 500 gr of alcoholic infusion of walnut husks and pour into 100 l. eau-de-vie. Then add 25 gr. ammonia.
d) Infuse in 2 l. boiling water: 40 gr. of cachou, 60 gr, of a mixture with equal parts of black tea and green tea, 1 gr. of rhubarb, 1 gr. of alcès, 50 gr. nutmeg (or 5 grams of vanilla), 100 gr. of linden flowers. Add 1 l. of sugar syrup and pour in 100 l. brandy;
e) Add to 100 l. of the brandy the following mixture: 2 l. old rum, 2 l. of alcoholic infusion of walnut husk, 2 l. infusion of bitter almonds, 1 l. alcoholic infusion of 15 gr. of cachou and 8 gr. of Tolu balm. 3 l is then added of grape syrup and 25 gr. ammonia.
f) Add to 100 l. of the brandy the following mixture: A) 2 l. old rum, 2 l. of kirsch, 50 gr. of sugar, 10 gr. vanilla, after infusion of 2 days; B) decoction, in 2 l. of water, 500 gr. of licorice roots crushed and 120 gr. chamomile with 250 gr of brown sugar.
g) The rancio extract is composed of: 1 l. ‘eau-de-vie, 60 gr. of cachou, 10 gr. of Tolu balm. After 2 weeks of infusion, add 25 gr. of ammonia and introduce in 100 l. eau-de-vie.
After these various additions, the eau-de-vie must be strongly mixed, filtered and kept for a few months in barrels.
Instead of adding sauces to the eau-de-vie, we can, to aromatize it, pass the alcohol vapors out of the still through an aniser, cylindrical container containing a perforated basket in which one introduces aromatic substances (anise, juniper berries, raisin, etc.). A lid, fixed by simple means and easy to remove, makes it possible to quickly replace the basket. Alcoholic vapors enter the bottom of the appliance and exit through the upper part. By employing two anisers, the baskets can be reintroduced during operation, by isolating, in turn, by a system of valves, each of the appliances.
[Very much like a gin basket.]
This method is applied in Spain and South America for the preparation of aniseed spirits, as well as in the North of France for the manufacture of gins. Some rum distilleries from Cuba would also use it. Labat reports its application to the French West Indies in the early days of colonization. “When you want,” he writes, about the making of rum, “to make this eau-de-vie better and to remove the too strong odor and the acuteness that it has, one must be careful to wash the boiler and the condenser and suspend in the capital a bunch of anise or fennel and renew it every time the boiler is loaded.”
Artificial rum, consisting of good tasting industrial alcohol, flavored with chemical essences or vegetable extracts, was at one time the object of great consumption. Although it has almost disappeared in certain markets, particularly in France, because of strict laws relating to fraud repression, it is still found in Germany, the United States, and so on.
The easiest way to prepare artificial rum is to add rum essence to neutral alcohol. This is usually a mixture of formate and ethyl acetate, and sometimes ethyl butyrate is added. Ethyl nitrate has also been used.
Villon gives the following method of preparation of an essence of rum, which would have been used formerly in Austria. Mix 12 parts of manganese dioxide, 12 of sulfuric acid, 12 liters of alcohol and 4 kgs of 500 strong acetic acid. Seven liters of “essence” are distilled and collected, consisting mainly of formate and ethyl acetate.
According to another more complicated formula, 32 kgs of alcohol, 4 kgs of sulfuric acid, 2 kgs of manganese dioxide and 4 kgs of pyroligneous acid are mixed together. 32 kgs of saffron extract and 1/2 kg of birch oil are distilled and 32 kgs of the distillate are added (Fleischmann).
Gaber reports the following process for preparing artificial rum with commercial esters. Add to 100 liters of good tasting alcohol: 10 liters of water, 80 gr. of ethyl acetate and 100 gr. ethyl butyrate. Distill over low heat, so that it boils continuously and evenly, until the still contains only 10 liters of liquid.
According to the same author, one would obtain a more aromatic product, by distilling the following mixture: alcohol at 70° 100 liters, water 10 liters, ethyl acetate 80 gr, amyl valerianate 10 gr.
Esters are often replaced by infusions of various aromatic products.
Ratier (1) indicates the following processes:
(1) Manuel du négociant en apiritueux Paris 1863.
To mimic Jamaican rum, take 50 kg of cane molasses, 50 l. water, 1.5 kg of yeast, 1.5 kg of prunes, 250 gr. orange peel. Boil all, except yeast, for 5 to 6 minutes, and let infuse for 15 days. Then add 250 gr. of tanned beef leather, cut into small pieces, let infuse for another 15 days, then add 100 l. of alcohol at 90° and filter.
In another formula, it is added to 100 l. split alcohol: 125 gr. distilled tar, 100 gr. of poppy flowers, 100 gr. hazelnuts (roasted like coffee beans), 20 gr. crushed ambrette. It is allowed to infuse for 3 or 4 days and filtered.
To imitate the rum of the West Indies, take 300 gr. crushed oak bark, 20 gr. of cayenne pepper, 10 gr. of crushed cachou, 5 gr. of cloves and 15 gr. light tar and distill. Let stand for 15 days in 5 liters of alcohol, and then pour into 100 l. of reduced alcohol at 50°.
Basset gives analogous formulas. Macerate 4.5 to 5 kgs of new tanned beef leather and 600 – 700 gr. of ground new oak in 1 hl. of alcohol at 60°. After one month, during which the material is frequently stirred, water is added and the whole is distilled to remove a product of 1 hl. at 60°. The distilled liquor is lowered to the merchantable level by ordinary water or small waters, and colored with caramel. We can replace the beef leather with 1 kg of cachou and bring the dose to 1 kg.
[Small waters is an interesting addition here. That would add volatile acids and long chain esters to the spirit, it would likely even add a degree of tufo that would be laissez faire.]
The formulas above give products reminiscent of real rum. They can not deceive the somewhat sophisticated buyer, even at a simple tasting. The specific aroma of rum has so far not been artificially reproduced. These imitations, however, find, because of their cheapness, a rather large clientele in the working classes, unfamiliar with the taste of real rum.
To give more mellowness to eaux-de-vie, they are frequently added before they are delivered for consumption, with sugar syrup. The amount of added sugar usually does not exceed 5 p. 1000, and it is most often lower in the case of fine spirits.
The syrups used must be prepared with very well refined cane sugars and free of any after taste, or better with candy sugar, as used for great wines of Champagne. Sometimes, however, the sweetening of common eaux-de-vie is carried out with grape must or even previously clarified molasses (1 – 2 l per hl of brandy).
Syrups are usually obtained cold, by dissolving the sugar in brandy to a low degree. For example, it is possible to introduce sugar into a barrel with the quantity of spirits required, for the syrup to contain a fixed quantity of sugar per liter; the drum is rolled to complete the dissolution of the sugar. The latter dissolving slowly in alcohol, the syrups are sometimes prepared by mixing equal parts of water and sugar, and adding the product obtained from brandy. In all cases, it is important to clarify with an egg white paste, followed by filtration.
Sometimes the syrups are prepared hot, but we must be careful to heat them with steam and in moderation, to prevent caramelization of the sugar and too much loss of alcohol.
The eau-de-vie, if carefully distilled, is clear when leaving the still. It happens however quite often that following the manipulations to which it is subjected later (caramelization, blending, reduction, etc), or as a result of aging in barrels, it becomes cloudy: the brandy is then said to louche or bleue.
[bleue refers to blue distillates tainted with verdigris.]
This louche may be due to various causes. The most common offense is: (a) the use of a burnt caramel for coloring; (b) the use of insufficiently pure water containing calcareous salts for reduction, which give rise to the formation of an insoluble precipitate that is very slow to settle; c) an excessive dissolution of the resinous principles, yielded by the wood of barrels during aging; d) the presence of an excess of essential oils, belonging mainly to the group of higher alcohols.
[It is interesting that Kervegant does not mention an excess of very long chain fatty acids. This is mainly what chill filtration of whisky is attributed to.]
As regards the latter cause, it should be pointed out that certain spirits, in particular marc spirits, which are very laden with essential oils, possess an opalescent hue, even at the exit of the still. An excessive exhaustion of the fermented must and a faulty fractionation of the tail products, are also likely to cause the louching of the eaux-de-vie normally not rich in essential oils. Blending as well as reduction, by causing the saponification of esters and reduction by the lowering of the alcoholic degree, decrease the solubility of essential oils and can cause louching, especially if these operations were brutally conducted.
It should be noted, again, that when put into service, a new still generally gives a more or less louched eaux-de-vie, as a result of the attack on copper by the acids of the hot wine. The device “is done” by the way quite quickly, the copper forming with organic matters and the salts of the must a protective coating which prevents it from being attacked further.
The “blue” hue of certain eaux-de-vie comes from the use of poorly cleaned stills in which it formed, during a work stoppage, a greyish green patina. It can also result from the action on copper of the ammoniacal vapors released during the distillation of musts abandoned too long for spontaneous fermentation. In general, the color disappears with time, leaving a deposit that can be separated by decantation.
Finally, V.-H. Veley and L.-Y. Veley (1) reported the presence, in 75° rum samples received in England, of a fungus which they called Coleothrix methystes and which would be the cause of the disorder of the liquid. This organism, however, would only intervene, according to N. Deerr, in very exceptional cases. It appears in the form of filaments or mucilaginous masses, remaining suspended in the rum, when the alcoholic degree is lowered.
(1) The microorganisms of faulty rum, London 1898.
[My theory is that they simply found the remnants of meat in Guyana rum. My understanding is that all N. Deerr confirmed is that these was cellular material and not that it was from a fungus.]
There are two methods to obtain the clarification of eaux-de-vie: filtration and fining.
Fining. [Translated from collage]
Finining consists of, adding to a liquid, substances which fix on their surface, either by molecular attraction or by simple entrainment, the tenuous particles incapable of precipitating themselves.
In the treatment of eaux-de-vie, fish glue, or isinglass, is mainly used at a rate of 2-3 gr per hl; gelatin, less fine, at the rate of 20-30 gr per hl; egg whites, at a dose of 2 to 2 1/2 per hl; and among mechanical clarifiers, pulverized wood charcoal (400-500 gr / hl) and diatomaceous earth (200 gr / hl). The latter has given very interesting results to Pacottet and Guittonneau, in the treatment of marc spirits, usually very difficult to clarify because of their high content of essential oils. It is important to use only earth neutral to taste and smell, purified beforehand by washing with ordinary water, then with distilled water and finally with alcohol.
Clarifying matter, after being disgorged, if necessary, is rinsed in a little water to eliminate odors, is dissolved in warm water, then diluted with brandy. It is then introduced in small quantities into the liquid to be treated, vigorously stirring the mass after each addition, by means of wooden stirrers. The time required to obtain the complete precipitation of the deposit depends on the dimensions of the containers in which the fining is carried out and the fining aid used. It takes an average of 10 to 20 days, and up to 30 days with isinglass, to get a complete clarification. We then proceed to racking. The operation is sometimes aided by subjecting the liquid to filtration.
Fining makes it possible to obtain very shiny eaux-de-vie, having lost none of their bouquet; it is remarkably suitable for the treatment of spirits. It unfortunately has the disadvantage of being slow and causing a decrease in color and alcoholic degree (0.5-1°). In practice, it is hardly used unless sufficient clarification can be obtained by simple filtration.
Filtration allows having spirits that can be delivered immediately for consumption.
Very simple filters, working without pressure or contact with air, are generally used.
Conical filters are formed by cone-shaped metal containers, whose large base is turned upwards and whose opposite end is pierced with an orifice provided with a tap. Inside a flannel shoe is suspended.
A discharge filter is a cylindrical device, divided into two parts by a false bottom pierced with several holes, each receiving a socket on which is attached a pendent shoe. The alcohol is poured into the upper reservoir and, under the influence of its own weight, filters through the breeches and accumulates in the lower reservoir, from which it is withdrawn.
The charentais filter is also constituted by a cylindrical container made of wood or tinned copper, of low height, divided into two parts by a flannel disk or a leather chamois. The lower part is usually filled with paper pulp. The alcohol arrives at the bottom and, after having passed through the paper pulp and the disc, accumulates in the upper part, from where it leaves by an overflow orifice or a siphon. The flow of the liquid is obtained by slightly lifting the feed tray or immersing the filter at the top of the tank containing the brandy. In the big cellars of Cognac, the brandy undergoes 7 to 8 successive filtrations.
[This technique must be very 19th century.]
The filters above can be bonded with paper pulp, pulverized charboal coal, or diatomaceous earth. The bonding material is diluted with water so as to obtain a clear paste which is poured into the filter. The brandy that passes first is cloudy and needs to be filtered again.
[SOS It is hard to say what is happening here. Either they are creating a composite filter by stacking different times of material or they are adding a fining agent as a filtering aid. We do get some clues from a French speaking colleague:
As you wrote, they seem to talk about adding a fining agent as a filtering aid, and this is what I went too because of the word “encoller” they used: it most frequently means “to put glue on something” as “coller” generally means “to glue”, but in this case it must means “to incorporate a fining agent” (which is a very specific occurrence), as in the context of spirits, “coller” means “to use a fining agent”.
It may be in order to have a very intimate contact between fining agent and its target(s), originally dispersed in the volume and hard to catch, but soon to travel through the filter and in this case easy to reach (transpose to policemen, at first trying to find someone in a moving crowd, and on a second time at the door of a festival scanning the people one by one: it’s much easier for them to catch someone then, as EVERYONE as to travel in front of them sooner or later).
And, to complete the panel, maybe they try to improve the nature of the filtering mass by adding this fining agent in the hope that it acts as a prefilter or a “reticulation” agent, making the matter more tough, reducing the pores’ diameter and thus improving efficiency and/or reducing channeling which is a phenomenon that may very well happen with depth filtration.]
In filters without pressure, eau-de-vie slowly circulates in contact with the air. If the resulting oxidation improves the bouquet of the product, there is at the same time a loss of alcohol. Also, for the treatment of less fine-quality spirits, preference is often given to pressure filtration, working away from the air, which will have a much higher efficiency and minimal alcohol losses. There are many models of these devices (filter presses, bag filters, plug filters, etc.), which are connected by rubber hoses, with the feed placed on a upper level, and the receiving cask located below the filter.
When louching is produced by an excess of essential oils, filtration and fining often remain ineffective. Undissolved materials, can form a stable emulsion with the liquid and pass through the filters and are not always fully entrained by the fining aid.
[Essential oils in this case are likely fusel oils. aka higher alcohols.]
In this case, we often arrive at satisfactory results, stirring the liquid with a substance capable of fixing the essential oils, like some smectic clays and especially the light magnesia of commerce, then passing it through a filter loaded with the same filtering substance.
[Smectic clay is bentonite which is a common fining aid. I’m not sure about the magnesia.]
However, the method of choice for obtaining clarification is refrigeration. The vessel containing the eau-de-vie is surrounded by a thick layer of crushed ice, mixed with cooking salt, so as to lower its temperature to a few degrees below zero, and immediately upon achieving this temperature the liquid mass is filtered on light calcined magnesia. The eau-de-vie is then clearly opalescent, but the filter layer charged with magnesia, retains in passing all the impurities of the alcohol separated from their solvent at the temperature of the operation, and the clear liquid which is obtained does not louche again at a higher temperature.
[Chill filtration is the industry standard these days.]
Treatment of defective eaux-de-vie.
Spirits with bad tastes, odors or discolouration generally require treatment other than fining or filtration, which is sometimes sufficient when these defects are not very marked.
Bad taste. — The bad tastes that we meet most often in the eaux-de-vie are the piquant taste, the musty tastes, metal, burnt, fat, putrid smell.
The piquant taste commonly found in rums is due to the production of acrolein during the fermentation or distillation of musts, when the temperature is high. It usually disappears during aging, if it is not too accentuated.
[This is also found in whiskeys where they call them peppered. The INRI of Martinique attributed it to Corynebacteria which produces acrolein.]
The musty taste and odor, the acrid taste are due either to the use of poorly preserved vinasse or molasses, or to the uncleanliness of the cask. They are very difficult to remove.
[Many people want to torture their dunder, but here we see a non-specific warning of the consequences.]
The taste of metal, also called the boiler or copper taste, comes from the dissolution of copper salts during distillation. It happens in new stills or in those that have been out of order for a time, and have not been cleaned before use. It is often accompanied by blue tinted alcohol. To avoid this, it is important to always distill pure water before putting the appliance into operation.
Burnt taste is observed in spirits obtained with discontinuous appliances, when the distiller negligently leaves materials (lees, marcs, etc.) in the bottom of the boiler. It is due to the formation of tarry and empyreumatic products. It is rare in rum distilleries, where one usually sends clear musts to the still.
The taste of fat and the taste of oil are found especially in alcohols distilled by means of stills heated by direct steam. The oil used for the lubrication of the steam engine can pass into the exhaust steam and be driven by the alcoholic vapors. It is also necessary to incriminate sometimes cane grinder grease (distillery of cane juice) and butyric infections.
[I wish I knew more about butyric infections as a flaw. I suspect it could regard infections that produce butyl higher alcohols as opposed to a fatty acid.]
The putrid odor occurs in musts with too low acidity. Bettinger also observed it in Martinique in tanks that had received bagasse ashes to quench leaks. Although the mash is fairly acidic, the ashes, whose reaction is alkaline, manage to disrupt at the beginning the normal process of fermentation: there is formation of glycerin, aldehydes and sometimes even a smell of putrefaction. Finally, grand arôme rums, produced in the presence of a large quantity of more or less autolyzed yeasts, quite easily acquire the putrid taste. This is also one of the main pitfalls of making this type of rum.
[We learned earlier in the text about peptonization and how yeasts may be treated and broken down to overcome this issue.]
One can still point out: the sulfur taste, due to the presence of sulfur compounds in the eau-de-vie: the bitter taste, resulting from an excessive production of aldehydes and which shows up quite often when the vats spend some time under microbial veil before being distilled (Bettinger); the yeast taste, coming from the decomposition of the nitrogenous matter suspended in the must (yeast cells, etc. during the distillation, etc.);
[This last bad taste is the dreaded tufo.]
To rid the spirits of their bad tastes, we mainly use charcoal filtration. For the musty taste, it is preferred to add per hectolitre 500 gr. of charcoal powder, washed beforehand and diluted in 1 liter of eau-de-vie. Shake several times for 2 or 3 days, and finish by fining. Olive oil, at the dose of 1/2 liter per hl, as well as paraffin, pure and free of any shale odor, are also good absorbers. The latter must be used hot, at the temperature of 55°, which is its melting point.
[In the very olden days, possibly 19th century, some wines were shipped with olive oil floating above the wine as a preservative.]
For the purification of eaux-de-vie, we may still use oxidants in general (especially hydrogen peroxide and permanganate) and hydrogen in the presence of a catalyst. In the case of certain bad tastes (metal taste, for example), it is preferable to subject the spirit, brought back by addition of water to about 25°, to a new distillation. In other cases (sulfur taste), it must be treated with lime, potash or soda, but without reaching the point of neutrality.
Finally, it should be noted that some bad tastes are masked (acrid taste, copper taste), by adding a small amount of ammonia to the eau-de-vie.
Woody eau-de-vies. — Eaux-de-vie which have remained too long in new, unbroken in barrels, contract an astringent flavor and a too dark. Both a portion of the color and tannins are removed by finely pulverized charcoal treatment followed by filtration. If the “boisage” is not too pronounced, a simple fining with gelatin or isinglass is enough. One can also use olive oil, in the proportion of 100 gr. per hl. : shake quickly, then immediately decant the oil that floats.
Acidic eaux-de-vie — These come from the distillation of musts that have undergone acetic acidification, or use for the rehabilitation of pricked casks. Rums obtained in the past by the fermentation of the defecation foam were often acidic. To correct this defect, milk of lime or chalk powder was added to the eau-de-vie, in such proportion that the spirits remain acidic to litmus; it is stirred for a few moments, taken off after standing and distilled.
[I have never seen this regarding making rums with skimmings. Skimmings could possibly have yielded instant grand arôme rum. The old literature also mentions that skimmings, which had a sugar content, often fermented and went acidic which would likely constitute a large amount of acet acid in addition to the long chain acids from the breakdown of the cane wax. The big mystery in Jamaican grand arôme rums is how do they get rid of all the vinegar when not using H.H. Cousin’s “high ether process”?]