The Birectifier in Rum Manufacture (1945)

The birectifier can be purchased here as a kit for $2100USD. This is part of an ongoing series to fully explore and document the tool.

I have long collected papers from Rafael Arroyo which were pretty much lost and not indexed by google. I thought I had them all until I got new leads when I bought a rare hardcover first edition of Studies on Rum from the estate of a Seagram employee. Tucked inside was an ancient photostat of the third article digitized here. From two references on that document, I found the others.

Arroyo, himself, talks up the birectifier seemingly hawking & peddling from beyond the grave. He attributes the tool to Dr. Luckow who he no doubt corresponded with, but Karl Micko already had a slightly less refined version of it. My version, from an old engineers drawing, has some pretty specific diameters to make it all function correctly. I had my prototype before discovering the photostat and sent it back to to be fitted with more contemporary fittings they didn’t have way back then such as a ball joint for the condenser and threaded thermometer fittings. What we came up with is spot on and other things are falling into place, such as modern temperature controllers, and an eventual automation kit to reduce active time collecting all the fractions.

The Birectifier in Rum Manufacture (1945)

A Tool of Many Uses in Distilleries from Yeast Selection to Regulation of Quality and Maturing Period
By Rafael Arroyo, Ch.E., S.E.

The birectifier (Dr. Luckow’s) is a small laboratory fractional distillation unit, so constructed as to be capable of extremely high rectification and dephlegmation during fractionation. Its manipulation is very simple. After having used this apparatus for over nine years of research in rum manufacture we are ready to pronounce it the most valuable single tool available for this kind of investigation. Its introduction into the routine work of rum distilleries would represent a great step forward in the scientific control of manufacture, and in the production of standard types of rum of the highest uniformity in chemical composition and quality. How this unique piece of laboratory equipment helped solve many of our most intricate research problems will appear in a research bulletin now in preparation for the press, under the auspices of the Experiment Station of the University of Puerto Rico, with which the writer was connected as director of industrial chemical research from 1931 to 1944.

Meanwhile, the present article will deal with our views as to the services the birectifier could render to the rum industry. Let us start with a consideration of the important subject of yeast selection for the rum distillery. In general terms we may define a veritable rum yeast as one fulfilling the following requirements:
(1) producing a fair yield of alcohol, based upon the total sugar content of the substrate, in a fermentation period of reasonable length;
(2) producing a raw distillate capable of acquiring the desired degree of maturity in the shortest possible curing period;
(3) the raw rum thus produced should possess a well balanced chemical composition; and
(4) the yeast should be a fair producer of rum oil.
The rum distiller, therefore, should have means of ascertaining whether the strain he intends to use, or is already using, meets these requirements. The first two requirements are comparatively easy to investigate, although sometimes at the expense of much time and money losses; but not so the last two. And what makes this investigation so difficult is the fact that the ordinary routine analysis, as now executed in most distilleries, is of itself of very little help for purposes of quality determination and appraisal of a given rum. It gives meagre and sometimes misleading information about the chemical composition and balance of the spirit, and as to detection of the presence or absence of the important rum oil in the sample, the routine analysis is absolutely inadequate. Here is where the intervention of the birectifier becomes so important and beneficial by supplementing the ordinary analysis with the fractional distillation of a portion of the sample under the conditions provided by this apparatus.

The fractionation of a rum sample is carried in the birectifier in the following manner: The sample is diluted with distilled, neutral water, to an alcoholic concentration of 40.0 percent by volume. Then 250 milliliters of this solution are placed in the distilling flask of the birectifier, and the liquid is brought to a gentle boiling by carefully heating with a gas flame whose intensity and volume may be readily controlled by the operator. The distillation is so conducted that 25 milliliter portions are collected at intervals of fifteen minutes, so that eight fractions of 25 milliliters each are collected in two hours’ fractionating period. The fractions are collected into graduated glass cups provided with glass covers. During the fractionation of the sample some important observations are recorded:
(1) temperature range within which each fraction passes over;
(2) characteristic aroma of each fraction;
(3) presence or absence of turbidity or opalescense in individual fractions;
(4) appearance of oily droplets floating over the surface of individual fractions;
(5) odor and appearance of the residual liquid left and appearance of the residual liquid left in the distilling flask.
The various fractions are then diluted to one hundred milliliters with distilled, neutral water, and the characteristic odor and physical appearance of each fraction is re-noted. After this, each fraction is submitted to chemical analysis for the determination of:
(1) alcohol percentage by volume;
(2) total acidity;
(3) esters;
(4) aldehydes;
(5) higher alcohols (fusel oil).
The constituents thus determined, with the exception of the ethyl alcohol, are expressed in milligrams per 100 milliliters of undiluted distillate.

From the analytical data thus obtained a more intimate knowledge of the true chemical composition of the rum sample is gained, and certain important ratios and relations among the constituents of the rum taste and aroma are determined. These ratios and relations have a direct connection with the quality of the fractionated spirit, and offer a clue by which the rapidity with which the given raw spirit will mature may be predicted. The fractional distillation reveals also the important question of presence or absence of rum oil in the sample; and when present, if in generous, moderate, or meagre amounts. It will be found that the first fraction contains most of the esters and aldehydes of low boiling point and low molecular weight, besides a large amount of ethyl alcohol. The second fraction has a similar composition to the first, but the amount of esters and aldehydes is much diminished. The third fraction is practically made up of ethanol, with traces of aldehydes, esters, and higher alcohols. The fourth fraction could be called “the higher alcohols fraction,” as from 70 to 75% of all the higher alcohols present in the sample will make their appearance in this fraction. The fifth fraction may be said to regulate the quality of the sample as a beverage, for here we find the major part of the esters and aldehydes of high boiling point and high molecular weight which play such an important role in rum taste and aroma; what is still more important, we find here also the major part of the invaluable rum oil. Fractions sixth to eighth will be made up mostly of water with a little ethyl alcohol and very minute amounts of very high molecular weight, high boiling point, esters and aldehydes. However, when the rum sample under fractionation has been poorly fermented or distilled, these fractions will contain malodorous substances derived from protein degradation and decomposition products. If these latter substances are present in liberal amounts they may tend to mask the aromatic effect of the other rum ingredients mentioned above.

What has been stated above shows at once the importance of the birectifier in the scientific selection of a suitable yeast for the rum distillery. The fractional distillation work with its help will prove that different strains of yeast will produce different products of metabolism other than ethanol, and that this difference is related not only to the amount of these by-products, but more particularly to the kind. These secondary products of alcoholic fermentation taken as a whole form what has been nominated “the non-alcohol-number” of a given rum sample and it is to this “non-alcohol-number” that rum owes its peculiar aroma and taste. Hence the importance of having accurate means at our disposal to investigate thoroughly the “non-alcohol-number” produced to by the yeast selected to manufacture our rum.

In the first part of this article it was demonstrated in what manner the birectifier could be of invaluable service to the rum distiller in the important work of yeast selection. This second part treats of how the Luckow birectifier will be of equal or greater help in following the maturing process of the raw distillate during its curing period under natural aging in the traditional oak barrel. When freshly distilled, the raw rum possesses inherent characteristics by which the experienced distiller may judge not only its value and quality as a raw spirit, but also may predict the probable aging period in which the raw will mature. This is only possible, however, if the distillery is equipped with a Luckow birectifier and with personnel experienced in its use and in the interpretation of the results obtained during the fractional distillation, and analyses of separate fractions. Undoubtedly the birectifer will greatly facilitate the task, and will besides direct the distiller to the necessary changes or improvements in his manufacturing methods to secure the proper type of distillate. When these conditions of proper chemical composition in the raw spirit are not being attained, the necessary changes, alterations, innovations, or modifications, may involve a substitution of the fermentation agent itself, or different techniques of fermentation and distillation, or even pre-treatment or change of the raw material used for mashing.

Since the cause of a poor chemical composition and balance in the raw distillate may have its origin in such diverse sources, it is evident that without the proper orientation, the correction of these conditions may be very complicated and obscure task for the distiller. This will not be the case, however, if he knows how to use a Luckow birectifier and interpret and analyze the results. Up to the present time the distiller has been guided in most cases by his senses of taste and smell, perhaps by the routine analysis of the raw distillate. While the organoleptic tests for rum aroma and taste are undoubtedly of great value when performed by the right person, their subjective nature disqualifies them for the detection of minute but often important irregularities in the chemical make-up of the sample which bear a direct influence on the quality of the spirit. This will be especially so when the person or persons performing the organoleptic tests are also responsible for the production of the rum.

As to the routine analysis as performed in most rum distilleries, its influence on the appraisal of quality is almost nil. Our experience has shown us that two samples of rum of apparently identical chemical composition as disclosed by their respective routine analyses, may actually prove as different as night is from day. This is due to the fact that the routine analysis really gives but meagre and often misleading information as to the true constitution of a given rum, and may make two rums which are really very different appear as of identical chemical composition. If it is thus so difficult to ascertain the merits of raw rums by the ordinary means used, it becomes infinitely more difficult to judge their ability for quick maturing merely from consideration of organoleptic tests and the results offered by the routine analysis. The routine analysis merely informs us that a certain raw distillate possesses a given degree of alcoholic concentration, besides certain amounts of aldehydes, esters, acidity, and higher alcohols. These ingredients are expressed respectively under collective terms: aldehydes as acetaldehyde; esters, as ethyl acetate; acidity, as acetic; and higher alcohols, either as amyl or isobutyl. Nothing is indicated as to the presence or absence of the most important rum oil in the sample. But research workers have demonstrated that the true chemical composition of rum is so complicated that many of its components (and these presumably the most important in determining quality) are still undiscovered or undetermined. Those that have been found to appear in different rums, from different countries, produced by different fermentation and distillation methods, and from different raw materials, are given below. Of course, no single rum sample would contain all of these substances. The several groups of rum constituents other than ethanol and water are as follows:
A. Acetals: acetal.
B. Alcohols. Monohydric Saturated Alcohols: methyl, propyl (normal), isoproply, butyl (normal), isobutyl, amyl (normal), amyl (secondary), hexyl, heptyl, octyl, decyl.
C. Aldehydes: acetaldehyde, propaldehyde, isobutaldehyde, butaldehyde, hexaldehyde, heptaldehyde, butaldehyde, hexaldehyde, heptaldehyde furfural.
D. Ketones: acetone.
E. Organic acids, saturated aliphatic series: formic, acetic, propionic, butyric, caproic, heptoic, caprylic, capric.
F. Esters: (1) Acetates of methanol, ethanol, propanol, butanol, isobutanol, pentanols. (2) Propionates of methanol, ethanol, pentanols. (3) Formates of ethanol, propanol, butanol, pentanols. (4) Butyrates and isobutyrates of ethanol, pentanols. (5) Oenanthate, caprylate and caproate of ethyl alcohol.
G. Bases: pyridine, amines.
H. Essential Oils: rum oil, other essential oils.

The foregoing list of possible components of rum taste and aroma will indicate the broad generalization effected by the conventional method of reporting rum analyses according to the routine way. Among the components listed are some detrimental, others of a neutral influence, and some beneficial to rum taste and aroma. Therefore, it is not so much the amounts of group constituents reported under conventional methods of analysis that count, but rather the kind and amount of the individual constituents in each group and the ratios existing among individual components and group components. To acquire this type of information, fractional distillation and individual component determinations become absolutely essential, and for this work no better tool is available than the Luckow birectifier. The data obtained from the proper fractionation of the sample serve to draw a set of curves which, taken together, produce a graphic representation of the sample’s chemical structure. These graphs and analytical data are kept for comparison with other future similar data and graphs obtained at periodical intervals during the ageing period. By this means, the exact time at which the rum acquires full maturity may be ascertained closely, at a savings of much time, money and labor.

The initial chemical structure of the raw distillate will be the essential factor in obtaining early or late maturity during the aging period, other factors affecting the maturing process being constant. This is the reason why in industrial practice we find raws that reach full maturity in a very short period of curing (in from two to three years), while others under similar conditions take twice or even thrice this time. Hence, it becomes a matter of the utmost importance to have means to appraise a given raw distillate as to its inherent maturing capacity and qualifications during curing; and if the raw spirit shows not to be a quick maturing one, to make the necessary changes or innovations in the culture, manufacturing methods, or raw material used, so as to secure the desired chemical constitution of the raw spirit that will guarantee rapid attainment of the mature condition. The state of maturity may be judged in genuine rums from an examination of the true chemical constitution; but more so by the ratios existing among different constituents and group constituents. For instance, a raw distillate will be a fast maturing rum under natural aging if it fullfills the following requirements:
(1) A low, or moderate numerical value (expressed in milligrams per hundred milliliters) in the constituents of the first fraction.
(2) A low ratio of first fraction components to those of the fifth fraction.
(3) A high ratio of total non-alcohol-number to the members composing the fourth fraction
(4) A high ratio of esters to volatile acidity and to aldehydes.
(5) Presence of liberal amounts of rum oil in fractions five to eight inclusive.
(6) Absence of malodorous bodies in fractions six to eight inclusive.
(7) High ratio of high molecular weight esters and aldehydes to low molecular weight esters and aldehydes.
The information necessary for this kind of chemical control in the distillery is greatly facilitated by the introduction of the Luckow birectifier into the daily, routine work of the distillery laboratory.

As the raw rum matures in storage, the successive fractional distillations performed at intervals of three months’ time, will show the manner in which the raw spirit reaches maturity. At first there will be great changes in the composition of individual fractions and of the amounts of individual components present in different fractions. The graphs showing these changes will be quite different also. But these differences will become less accentuated and striking as time passes and the maturing process goes on, until the time comes when the rum constituents show such states of balance and equilibrium that differences in analytical results and in the shape of graphs become so inconspicuous as to be insignificant. At this point the rum has reached maturity, and we may expect and hope for very little improvement of taste and aroma thereafter. It is true that it takes time, labor, and expense to follow in this manner the maturing process of the raw rums in industrial practice; but at the same time the work is highly interesting, very enlightening, and above all profitable. Therefore the adoption of this method of chemical control is to be recommended to all rum distilleries. There is no question that through its use rums of more stable composition and of better quality will be produced.

[The last article was from the journal, Sugar. International Sugar Journal turned around and put this next brief article in their notes section. It paraphrases the above but adds weight to the recommendation.]

The Birectifier in Rum Manufacture.
Rafael Arroyo. Sugar, 1945, 40, No. 4, pp. 38-40 and 41.

Dr. Luckow’s birectifier is a small laboratory fractional distillation unit, so constructed as to be capable of extremely high rectification and dephlegmation. Its manipulation is very simple, and after having used it for over nine years’ research work in rum manufacturing, the author pronounces it as the most valuable single tool available for this kind of investigation. Its introduction into the routine work of the rum distillery would represent a great step forward in the scientific control of manufacture, and in the production of standard types of the highest uniformity in composition and quality.

In the present article information is give as to the service of the birectifier can render to the important subject of yeast selection for rum manufacture. A veritable rum yeast is one fulfilling the following requirements:
(1) it produces a fair yield of alcohol;
(2) it gives a raw distillate capable of maturing in the shortest time possible;
(3) it affords a rum of well-balanced chemical composition; and
(4) it should be a fair producer of rum oil.
Of these the first two are easy to investigate, but not so the last two. Ordinary routine analysis as now executed in most distilleries is of very little help for the determination of quality and the appraisal of a given rum. Its information is meagre and often misleading. Here is where the invention of the birectifier becomes so important and beneficial by supplementing the ordinary analysis with the fractional distillation of a portion of the sample.

Fractionation in the birectifier is carried out in the following manner: The sample is diluted with neutral distilled water to an alcoholic concentration of about 40 per cent. by volume. Then 250 ml. are laced in the distilling flask of the birectifier, and the distillation so conducted that 25 ml. portions are collected in two hours’ fractionating period. During this time some important observations are recorded on each fraction, viz.
(1) its temperature range;
(2) its characteristic aroma;
(3) its clarity, or turbidity or opalescence; and
(4) the presence of oily droplets;
lastly the odour and appearance of the residual liquid left in the flask are noted.

These various fractions are diluted to 100 ml. with neutral, distilled water, and the characteristic  odour and physical appearance of each is again noted. After this each fraction is submitted to chemical analysis for the determination of:
(1) alcohol percentage by vol.;
(2) total acidity;
(3) esters;
(4) aldehydes; and
(5) higher alcohols (fusel oil);
these constituents with the exception of the alcohol being expressed in mgrm. per 100 ml. of undiluted distillate.

This analytical data affords a more intimate knowledge of the true composition of the rum sample than could otherwise be obtained. Certain important ratios and relationships among the constituents of the rum taste and aroma are determined. These ratios and relationships have direct connection with the quality of the fractionated spirit, and offer a clue by which the rapidity of maturing may be predicted. Further, the fractional distillation reveals whether or not rum oil is present in the sample, and its approximate amount.

It will be found that the first fraction contains most of the esters and aldehydes of low b. pt. and low molecular weight. The second will have a similar composition, but with diminished esters and aldehydes. The third will be practically made up of ethyl alcohol with traces of aldehydes, esters and higher alcohols. The fourth could be called “the higher alcohol fraction” and from 70 to 75 per cent. present in the sample will appear here. The fifth may be said to regulate the quality of the sample as a beverage, for here are found the major part of the esters and aldehydes of higher b. pt. and molecular weight, and what is more important the major part of the rum oil. Fractions six to eight will be made up mostly of water, but when the rum under consideration has been poorly fermented or distilled these fractions will contain malodorous substances derived from protein degradation and decomposition products. If these are present in considerable amount they may tend to mask the aromatic effect of the other rum ingredients mentioned above. (In the second part of the article the author considers the value of the Luckow birectifier in following the maturing process of the raw distillate during its curing period in the traditional oak barrel).

[Arroyo replied to his own articles and whatever discussion it generated with this next piece.]

Dr. Luckow’s Birectifier.
An Indispensable Apparatus in Spirit Analysis and Research.
By Rafael Arroyo

[image taken from the photostat found in a hardcover of Studies on Rum owned by a Seagram employee]

Chemical analysis alone, as usually practiced, is almost entirely ineffective in the appraisal of the rum aroma, nor does it give any indication as to which particular constituents of the non-alcohol number of rums are mainly responsible for the nature of their flavours. Had it not been for our fractional distillation work with the help of the birectifier invented by Dr. Curt Luckow, of the Institute of Fermentology, Berlin, we would never have discovered the presence of the invaluable rum oil in Puerto Rican rums.

We intend, therefore, to review the application of this simple yet highly efficient piece of laboratory equipment to our investigations in rum manufacture. It would be proper to start with its description. Referring to the accompanying sketch, alcoholic vapours rising from the boiling flask A, through the top-sealed glass chamber B are forced to enter the air condenser C, from the top of which they pass down through the external glass coils shown, in which the condensation of the high boiling constituents takes place. A mixture of liquid  and vapour passes along tube D into the head-tube E; there the vapour rises up the neck-tube to pass on through the exit to the condenser and receiver (not seen in the sketch).

High boiling constituents in the liquid phase descend through the inner bulbed condenser F, and are returned to Flask A through the glass syphon tube G acting as a water seal. It will be seen that vapours arising from the boiling liquid in flask A are thus prevented from rising up through the inner condenser F. As may be seen, there are thermometers to take the temperature of the vapours in compartments C and E.

Fractionation is carried out in the birectifier in the following manner: The sample of rum is diluted with distilled water to an alcohol content of 40 per cent. by vol., 250 ml. of which solution is placed in the distilling flask connected to the birectifier, the liquid being brought to gentle boiling by careful heating with a gas flame of variable intensity. The distillation is so conducted that 25 ml. portions are collected at intervals of 15 minutes between fractions, so that eight fraction of 25 ml. each are collected in a 2-hour fractionating period. The temperatures of distillation at the start and finish of each fraction as well as the physical appearance of individual fractions are recorded. The different fractions are collected into graduated glass cups (that form an accessory of the birectifier), provided with glass covers. These have the shape of the tasting cups used by professional tasters of alcoholic beverages. During distillation of the sample observations are made, such as:
(1) temperature range within which each fraction passes over;
(2) characteristic aroma of each fraction;
(3) presence of turbidity;
(4) presence of oily droplets on the surface of the liquid of individual fractions.
Then the odour and appearance of the residual liquid left in the distilling flask are also observed, and the various fractions diluted to 100 ml. with distilled water, the characteristic odour and physical appearance being also noted.

Among the many constituents that enter into the composition of a genuine rum there is none so important as the essential oil, or mixture of essential oils, to which the name of “rum oil” has been given. Micko working with Jamaican rum found that all pure genuine rums of this class contained this oil in variable quantities, and that the specific odour of Jamaican  rum was due principally to this aromatic constituent. Our own work has proved that this or similar essential oil form the fundamental aroma of any genuine rum, and that some varieties of yeast will produce it in variable quantities, but always in very small amounts.

The use of the birectifier in yeast selection work makes it possible to detect its presence. We found that this essential oil usually appeared in the fifth fractions, and in some cases, when present in comparatively large amounts, in the sixth, seventh, and eighth fraction in successive decreasing quantities. It was always more noticeable in the fifth. In our yeast selection work it was a matter of great interest to ascertain the extent to which a given yeast was able to produce this substance. Using ordinary chemical analysis by official methods, the presence or absence of this valuable ingredient could not be identified.

The birectifier again becomes useful in the classification and appraisal of commercial or experimental rums, and in the case of the former ones in also becomes a valuable and convenient tool in the detection of artificially added aromatic and flavouring substances. We feel certain that if ever government regulation of rum quality is established by law in Puerto Rico, the birectifier will prove an invaluable asset in its successful operation, in this way protecting the public health.

[A lot more can be said, but I favor not diluting the fractions to 100 ml, but rather following later established ideas where 5 ml of each fractions goes towards an exhaustive test while 20 ml of each fraction goes towards conventional drinkable dilution. The highly alcoholic samples (1-4) are diluted from 20 ml to 60 ml by adding 40 ml while the low alcohol samples (5-8) are diluted 20 ml to 40 ml. Few small distilleries will be performing full on chemical analysis and will be mostly organoleptic. Procedures can change as analysis gets more sophisticated.]

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